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Hemi 5.7 overheating after new thermostat and air purge. #2853154
11/29/20 10:48 PM
11/29/20 10:48 PM
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Ok. Changed the thermostat and began sudden over heating that l didnt have before. So the video l found suspected air trapped. I got an Allen wrench and ratchet and pulled the purge plug above the thermostat and had some air, so l was excited that l resolved the issue. But on test run, the thermostat stayed middle like it should look, but the engine got HOT AND steamed and smoked from below the Coolant well. What is Going on?!?!?!?!.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853188
11/30/20 12:33 AM
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Bad thermostat maybe. Take it back out and put it in boiling water to se if it opens.You do have it installed like the picture right. What was the reason to swap the thermo to begin with?

thermo.jpg
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: stumpy] #2853191
11/30/20 12:45 AM
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This is the second try at the thermostat. Returned one in case that was what's wrong.
I put it in exactly as the first one came out.
The thermostat sometimes Reads right. And jumps up hot, then after an air purge and refill of fluids it will get got but stop at middle of the dial for temp. Like it's perfect temp but not.
I can pull it in the morning and check its positioning again. I have no prob checking that.
It appears to be right but lm no professional. I 'believe " I have put it in correctly. I can be wrong.
Rather be wrong and learn. Just wanna figure this out.
The thermostat Does work half the time. The other half of the time it acts like its perfect but l am boiling anyhow. Like it reading half the temp. Can you really get 2 bad thermometers in a row. Lol

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853192
11/30/20 12:46 AM
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I will boil it in the morning and look

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853194
11/30/20 12:49 AM
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You say the temp gauge reads correctly in the middle. Where is the water you saw? What are you referring to when you say coolant well? Engine should be running at about 210*. What year and model is the vehicle?

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: stumpy] #2853226
11/30/20 07:59 AM
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This is a very common problem on all 5.7 and 6.4 ( thermostat failure). When you drain the cooling system on these you have to be patient and bleed the system several times. It will take a while but its not a huge deal. I am curious about something though- I've changed thermostats on 2 separate 5.7 and a 6.4 and never had to bleed the system. I saw a clever backwoods way to do it. Just crack the housing off on the corner and hold a plastic ziplock bag under to collect coolant. When it stops running out ( yes, you have to clamp rad hose)
you can throw the new stat in, refill and be on your way.

Does it make a rushing water noise on start up ( noise from behind dash)?

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparjim79] #2853228
11/30/20 08:14 AM
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moparjim79 so just loosen or remove the bolt, or do you actually separate the parts at the gasket surface? Thanks

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparjim79] #2853273
11/30/20 11:22 AM
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Originally Posted by moparjim79
This is a very common problem on all 5.7 and 6.4 ( thermostat failure). When you drain the cooling system on these you have to be patient and bleed the system several times. It will take a while but its not a huge deal. I am curious about something though- I've changed thermostats on 2 separate 5.7 and a 6.4 and never had to bleed the system. I saw a clever backwoods way to do it. Just crack the housing off on the corner and hold a plastic ziplock bag under to collect coolant. When it stops running out ( yes, you have to clamp rad hose)
you can throw the new stat in, refill and be on your way.

Does it make a rushing water noise on start up ( noise from behind dash)?



DId same thing on my Magnum with 5.7 . . . just took the bolts off, got the housing loose and let coolant drain into ziplock bag . . . pulled old stat, put in new stat (making sure gasket around stat is in place correctly), put on housing, bolted up, and added the coolant from ziplock bag to overflow . . no issue.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: stumpy] #2853286
11/30/20 11:57 AM
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Do you see the recessed Allen behind the thermostat housing?

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853416
11/30/20 03:48 PM
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Originally Posted by KcCrown
Ok. Changed the thermostat and began sudden over heating that l didnt have before. So the video l found suspected air trapped. I got an Allen wrench and ratchet and pulled the purge plug above the thermostat and had some air, so l was excited that l resolved the issue. But on test run, the thermostat stayed middle like it should look, but the engine got HOT AND steamed and smoked from below the Coolant well. What is Going on?!?!?!?!.


If I understand what you've posted correctly it doesn't sound like the thermostat is the problem.

You don't specify what kind of vehicle it's in.

You say that the temperature gauge is staying in the normal range.

Guessing that it's a car (Charger, Magnum, 300).

Is there damage (crack, hole) in the coolant reservoir anywhere?
There are two chambers in the reservoir, one pressurized and one is the overflow bottle.

The pressurized is obviously where the radiator cap is.
If there's a hole or crack in it the cooling system won't build pressure.

The side closest to the outer fender is the overflow area.
If it looks full cooling system pressure has filled it, it shouldn't be full.

You need to know exactly where the coolant is coming out from.

You also need to check the system with a coolant pressure tester.

It will help diagnose where coolant is coming out at.
You can probably rent one from an auto parts store (usually rental is free with a deposit).


Kayse can't keep up at all now. lol
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: a12rag] #2853489
11/30/20 06:18 PM
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I replaced thermostat and things are fine for 2 to 3 weeks.. then, suddenly overheat.
I suspect l have air locked in system. I finally got Allen wrench to break the bleeder open and thought it was fixed, then over heated. I will bleed again now and continue to try to resolve this. From everyones info it very likely is a air pocket l have to get all the way out.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: a12rag] #2853494
11/30/20 06:30 PM
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My cousin who knows a lot more than l basically did this . He cracked the housing and bled it off this way and it worked a while. He did it several times and it lasted a mnth. So basically it seems somehow after a mnth of running l pull air somehow and have to deal with this again. Is my fluid getting too low and then sucking air? Not sure . For now l am gonna pull the bleed bolt again and do it several times and see if l can get all the air out. This MUST be what's wrong from everything l have read. When l change the thermostat out it seems to resolve for a while. But not always. Now lm using the bleeder bolt and seeing if this is a better location at higher level above the thermostat level to get it all out. Fingers crossed.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: a12rag] #2853498
11/30/20 06:33 PM
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This basic method seems to work for 3 to 5 weeks then sudden issue. Like somehow l pull air into the system over time or suddenly after several seeks. Is the fluid getting low and allowing air in. ? Do l need to keep my eye on the fluid level constantly.?
My 5.7 has a bleeder bolt right above the thermostat housing. I am TRYING TO bleed it out from that. This is 3rd attempt. It seem to be taking many times bleeding. But that sounds normal maybe

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853503
11/30/20 06:48 PM
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If you are not loosing coolant and it stays full you might have head gaskets or cracked head. You can get a test kit that will show if there is combustion gasses in the coolant.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853505
11/30/20 06:54 PM
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On my 06 Magnum, I followed the service manual instructions. You open the bleeder, fill the reservoir and let the coolant drain into the car until it comes out of the bleeder. I did this over a year ago when I changed my water pump and thermostat. Never had any issues. It took all afternoon, but it worked.


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Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: NITROUSN] #2853537
11/30/20 08:15 PM
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Coolant drops into system normal and has to be refilled. No fluid in oil whatsoever. 1

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: GTSDart340] #2853538
11/30/20 08:17 PM
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This what l am doing. However. I open the bleeder and it flows out the bleeder and l fill it. I start the car and right away steam from under the engine.. gauge doesnt even rise much before the engine and fluid are obviously hot. I shut it down. Am waiting to cool down to pull the bleeder again. So far all 3 times lve done this, l have air again to bleed. Not sure [censored].

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2853539
11/30/20 08:23 PM
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No leaks are apparent. Fluid stays full and pressurized.
Fluid only drops after the engine warms and the thermostat opens. Then it drops. Steam does roll up from the bottom if the engine once it's hot. Not sure why. But it doesnt seem to be a leak? It doesnt drop in level or pressure. It is under pressure. It seems like l might have air trapped and it may be taking several times to bleed it all out.
I dont get it.
This is its second thermostat. It acts fine for weeks after the thermostat is installed. Then 5 weeks after it suddenly over heats and acts like it has pulled air into it somehow. Then the air is trapped.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: GTSDart340] #2853540
11/30/20 08:25 PM
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So. Curiosity. What part took all afternoon. Did you have to open the bleeder several times like l am doing.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853541
11/30/20 08:25 PM
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Originally Posted by KcCrown
This what l am doing. However. I open the bleeder and it flows out the bleeder and l fill it. I start the car and right away steam from under the engine.. gauge doesnt even rise much before the engine and fluid are obviously hot. I shut it down. Am waiting to cool down to pull the bleeder again. So far all 3 times lve done this, l have air again to bleed. Not sure [censored].


Ok, KC, we are trying to help you, dont get frustrated. You have a breach in your cooling system. As stated above, at this point , get a pressure tester( buy or rent) pressurize it cold and if you have to, walk away from it for a while. Some pressure tests reveal the issue immediately, sometimes its a slow seep. I thought at first maybe you had a bad rad, but then you talk about steam from under the engine. This is the tricky part of online diagnostic steps. What one person sees as a problem someone more familiar with cars may see a slew of different issues all related/causing the "issue". Hang in there well get it. Go get your pressure tester boy!

Last edited by moparjim79; 11/30/20 08:27 PM.
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2853545
11/30/20 08:30 PM
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It doesnt seem like a thermostat or a leak. Pressure is fine. It's under full pressure.
Fluid doesnt go anywhere except through the engine when heated up. The thermostat opens and the fluid drops.
It seems like l must have air trapped and it is taking many times to bleed it all out possibly. ? I am hopeful this is all that is happening. But lm unsure yet.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: BB14404SPD] #2853550
11/30/20 08:35 PM
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Yes. This is what lm doing. On the 3rd time now

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: stumpy] #2853557
11/30/20 08:42 PM
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Initially, I overheated and had NO TEMP on the gauge dash at all. Total thermostat failure. Changed it and had no problem for 4 weeks. Then acted like l had air trapped. My cousin purged the air out the hose housing until it was almost fixed but not 100%. I then changed thermostat again in case l had a bad one... and everything seemed resolved for 3 weeks until a sudden over heat... so l went back to trying to purge and could get the Allen bolt to turn at first so l opened the thermostat up and filled it till it poured from there and it resolved again... then suddenly several days ago it overheated again. I finally got better leverage on the allwn bolt to purge air and am on my 3rd time purging air from there. It does have air when l open it, so ... l continue to purge it

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853561
11/30/20 09:10 PM
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I do t want to discourage you to much, but its becoming apparent you shouldn't be working on cars. Don't get upset, do exactly what we told you. If it seems like too much is there for you to deal with/ too involved, have a garage work it and save yourself the agony. Even the best shade tree wrenches get beat sometimes and need a pros help
.

You didn't get any CELs did you? Like a temp sensor or the like, right?

Last edited by moparjim79; 11/30/20 09:14 PM.
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853574
11/30/20 09:49 PM
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Read back to what I told you. My bets are combustion is getting into the system causing the air. You can get a simple test kit to see if it is combustion gas.

Test kit

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: NITROUSN] #2853598
11/30/20 10:40 PM
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Originally Posted by NITROUSN
Read back to what I told you. My bets are combustion is getting into the system causing the air. You can get a simple test kit to see if it is combustion gas.

Test kit


iagree

I agree, you may possibly have a head gasket issue.
A compression test and a block leak test would help identify if that's the problem.

Any idea if the water pump has ever been replaced?

Make sure that the weep hole on the bottom of the water pump isn't seeping coolant.

You said that steam was coming from below the engine.

The wife's Charger was using some coolant slowly and it was the water pump weeping coolant very slowly.


Kayse can't keep up at all now. lol
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: NITROUSN] #2853614
11/30/20 11:20 PM
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Originally Posted by NITROUSN
Read back to what I told you. My bets are combustion is getting into the system causing the air. You can get a simple test kit to see if it is combustion gas.

Test kit


Thought I was going crazy, but im not. People are not reading responses posted. I shouldn't be surprised.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparjim79] #2853624
11/30/20 11:47 PM
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Oh no worries at all . I'm not offended. I work on my own car only up to what lm able to diagnose and comprehend a s learn to do. After that l seek professionals. This SEEMED like a resolvable issue initially. But as l go, l am wondering what's really going on here.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2853625
11/30/20 11:53 PM
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My shop put in 3 new heads and sealed it all up brand new 3 months ago. New water pump. New head. New gaskets all around. New new new. Everything ran beautifully for 5 weeks. Then the first over heat but bad thermostat. I replaced the thermostat and all was resolved,,, for 4 weeks when it over heated but the thermostat worked and showed what was happening. This is when l found out about air getting trapped and purging. So now lve been trying to resolve it through purging air,
I agree that some of the behavior made me wonder about head gasket but.. it has full power, full pressure, no water oil mixing nothing else behaves head gasket leaking except the over heating itself.
Yes when l idle , it gets hot down under the engine. It stems from down below the engine and then the reservoir gets too hot and boils and steams pretty quickly. Even before the thermostat says so. The thermostat almost seems delayed.

It also seems like when l open the thermostat port it resolves it briefly.
Not permanently. This is why l kept thinking it was air.

So. Can l have a tiny head gasket leak that hides. ?
That doesnt draw power. Doesnt mix water and oil and takes a few days to draw air into the system before there is an issue?

Last edited by KcCrown; 11/30/20 11:56 PM.
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparjim79] #2853629
12/01/20 12:02 AM
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Not sure why l sound upset. I'm not at all. I'm totally good. I appreciate everyone input. That's why l came here. I am no mechanic and appreciate all the information. I guess sometimes typing reads different than how the person actually feels in their mind? Lol.. regardless. Dont worry about me. I am good. Keep sharing experience and info and l will keep trying ideas and trouble shooting with more information. Thanks.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparjim79] #2853630
12/01/20 12:05 AM
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Ok. Tomorrow a pressure tester. Sounds good. Will do. PARTS STORE maybe loan with deposit. Sounds good. That will answer that question. Makes sense

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853663
12/01/20 07:39 AM
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if it pressure tests good try jacking up the front of the car and do your bleeds again

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853698
12/01/20 09:30 AM
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Originally Posted by KcCrown
My shop put in 3 new heads and sealed it all up brand new 3 months ago. New water pump. New head. New gaskets all around. New new new.


Why are you even messing with it?

Take it back to the shop and have them fix it.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: Sniper] #2853800
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has the radiator cap been replaced, or is it the factory original ?
i have seen several caps that the seals were bad, allowing transfer of coolant into and out of the overflow, but also sucking air at the same time.
look closely at the radiator sealing surfaces as well, making sure they are ok and not nicked up.
lots of things to check, but you can do it !
beer

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853809
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Quote
So. Can l have a tiny head gasket leak that hides. ?


Yes and for the last time you need to have a test for combustion gasses in the cooling system. A pressure test will show nothing until the leak gets real bad. Simple logic here so read and listen. Cooling system pressure is minimal. Compression pressure could be 10 to 20 times greater. So what will leak first? Coolant in the cylinder or gasses in the cooling system. Your problem is not rocket science. You most likely have never had a bad thermostat. The thermostat needs to be immersed in coolant to operate correctly. Air that traps on the spring side will not allow the thermostat to open as scheduled. Instead it allows the engine to get to warm and possibly overfill the recovery tank and blow out before it opens. Continual bleeding of the air is just a temporary fix until more air gets in the system. You should never need to bleed after initial bleeding after repairs. Get the test done.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: Sniper] #2853885
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That doesnt help what so ever.

The answer is ... all that work cost 2grand and they will gladly charge me 130 an hour again. I needed to Try to resolve small issues on my own and fix small problems without purging cash out my ass. THATS WHY .
now that we are past that. Back to what's letting air in.
I have also read today that air can seep in around the Thermostat gasket area.. putting the thermostat in without and Gasket or goop in the seal can leak? Air can draw in there.
It does seem to pull air from somewhere without it being a big draw. Something small is allowing small amount of air into the system.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: NITROUSN] #2853890
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I think it's funny you are irritated. If you are cool assisting with information Thanks. If l am too stupid for you, Go away. Simple. Dont bother yourself. Lol. Crack me the hell up. I am A perfectly smart guy who has trouble shot this pretty easy. I grasp what everyone has said and lm working through the input one thing at a time and giving the car a chance to show me what is really happening, assuming nothing. I Am grabbing a pressure tester today. You say it should need to be bled very much yet people who also appear to have experience have shared that it can take all afternoon and several times bleeding and warming and bleeding which is time consuming. Requiring patience on my part while l look here for more information.
Based on what's happening with the car, l am more and more leaning towards a small leak right around the thermostat port. Where the pipe seals up behind the thermostat, could need a little gasket glue and not using anything right there might be allowing a tiny leak . It could potentially be that simple. There are several possibilities. And lm patiently working through each thing one at a time

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparx] #2853892
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I agree. It might be pulling air in a very simple place like this. I am working down a short list of these ideas. I appreciate everyones help.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853929
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Ok. MAYBE found it.

I pulled the second thermostat in 8 weeks....
To test it on the stove. .
I didnt believe it was that, because , seriously, 2 bad brand new thermostats in a row?? The more expensive one? Junk from the git go? But. It went up to temp, opened up and Stuck open. Froze in the open position. Removing it from the hot water, it refused to close back down. I had to force it to close l0ng after it cooled. So. I gotta assume a problem with the thermostat. This time I will but the gasket for it. In case there is any kind of air leak around the housing. And seal it up better on install.

Does everyone agree .. this could be what's wrong.? .

Bonefishmastr. When lm done putting in the new thermostat and using a gasket.. l am going to jack up the front to bleed it out. Maybe if l do all this stuff 100% on point . I can come away running like a champ.

Is there anything that can destroy thermostats? Just curious.

Last edited by KcCrown; 12/01/20 06:25 PM.
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2853944
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If it were me I would use a mopar t stat.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: mopars4ever] #2853982
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Originally Posted by mopars4ever
If it were me I would use a mopar t stat.


Why? Because Mopar stuff doesn't fail? Uhhhyeah.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparjim79] #2854006
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You really need to check for combustion in the cooling system.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2854160
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Originally Posted by KcCrown
Ok. MAYBE found it.

I pulled the second thermostat in 8 weeks....
To test it on the stove. .
I didnt believe it was that, because , seriously, 2 bad brand new thermostats in a row?? The more expensive one? Junk from the git go? But. It went up to temp, opened up and Stuck open. Froze in the open position. Removing it from the hot water, it refused to close back down. I had to force it to close l0ng after it cooled. So. I gotta assume a problem with the thermostat. This time I will but the gasket for it. In case there is any kind of air leak around the housing. And seal it up better on install.

Does everyone agree .. this could be what's wrong.? .

Bonefishmastr. When lm done putting in the new thermostat and using a gasket.. l am going to jack up the front to bleed it out. Maybe if l do all this stuff 100% on point . I can come away running like a champ.

Is there anything that can destroy thermostats? Just curious.
the one main thing that can destroy a t-stat .... CHINA

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: mopars4ever] #2854593
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Ok. Well. New thermostat new gasket. Not fixed.

Sigh.....

I am getting steam and coolant from way down under the block near the drivers side fire wall. It has to be leaking and have a breach in the coolant system/ up -down /in this location.
It is Under the booom and near the drivers side fire wall. What connects to the coolant system here? Heater core? A simple hose fitting? I need to jack this car up high and look at where it's coming out from. Simple ad that.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2854605
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Originally Posted by KcCrown
Ok. Well. New thermostat new gasket. Not fixed.

Sigh.....

I am getting steam and coolant from way down under the block near the drivers side fire wall. It has to be leaking and have a breach in the coolant system/ up -down /in this location.
It is Under the booom and near the drivers side fire wall. What connects to the coolant system here? Heater core? A simple hose fitting? I need to jack this car up high and look at where it's coming out from. Simple ad that.



Head gasket or freeze plug?


'68 Fury Convertible
'69 300 Convertible
'15 Durango 5.7 Hemi
'16 300 S Hemi
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2854655
12/03/20 06:06 AM
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Originally Posted by KcCrown
Ok. Well. New thermostat new gasket. Not fixed.

Sigh.....

I am getting steam and coolant from way down under the block near the drivers side fire wall. It has to be leaking and have a breach in the coolant system/ up -down /in this location.
It is Under the booom and near the drivers side fire wall. What connects to the coolant system here? Heater core? A simple hose fitting? I need to jack this car up high and look at where it's coming out from. Simple ad that.


The heater core is connected at the firewall at the back of the engine.

Have you used a pressure tester on the cooling system yet?

If there's a leak back there the tester should help you locate it.

If there's a leak it will push out coolant when hot and suck in air when it cools off.
The result is the overflow bottle will never work if there's a leak.

You need to figure out where the leak is.

That's what the pressure tester is for.
If it's pushing coolant out a exterior leak (freeze plug,external gasket leak, etc) you will see coolant drip.
It won't help find it if it's internal like a head gasket leaking into a cylinder.


Kayse can't keep up at all now. lol
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2854669
12/03/20 07:54 AM
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Originally Posted by SNK-EYZ
Originally Posted by KcCrown
Ok. Well. New thermostat new gasket. Not fixed.

Sigh.....

I am getting steam and coolant from way down under the block near the drivers side fire wall. It has to be leaking and have a breach in the coolant system/ up -down /in this location.
It is Under the booom and near the drivers side fire wall. What connects to the coolant system here? Heater core? A simple hose fitting? I need to jack this car up high and look at where it's coming out from. Simple ad that.


The heater core is connected at the firewall at the back of the engine.

Have you used a pressure tester on the cooling system yet?

If there's a leak back there the tester should help you locate it.

If there's a leak it will push out coolant when hot and suck in air when it cools off.
The result is the overflow bottle will never work if there's a leak.

You need to figure out where the leak is.

That's what the pressure tester is for.
If it's pushing coolant out a exterior leak (freeze plug,external gasket leak, etc) you will see coolant drip.
It won't help find it if it's internal like a head gasket leaking into a cylinder.



This^^^& also, under your intake manifold, there are 2 coolant crossover tubes that run from the timing cover to behind your engine, both have separate fittings that are quick connect plastic fittings.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: 3hundred] #2854807
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I really dont believe this is a head gasket. There is nothing going on in any other way to indicate head gasket. No powerless. No cross over to oil at all. Very clean oil. Full power and compression.
I did some reading and on this engine there is a Hose that runs exactly where lm describing that can break or split or get pin holes and do this. Also freeze plug is a possibility as well.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2854933
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Read above

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: moparjim79] #2854941
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The over flow cap itself is leaking a little as it comes up to.pressure. the leak is running down the line that goes towards the firewall and dripping on the exhaust manifold. This could honestly be as simple as a Failing Cap. I am running to get a brand new one. I have not pressure tested yet only because my gut believes l have full compression and am chading a simple leak in the system. Process of illumination however if this doesn't cure my ills l will have to go get the test kit next. No options left after this.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2854982
12/03/20 10:00 PM
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Originally Posted by KcCrown
The over flow cap itself is leaking a little as it comes up to.pressure. the leak is running down the line that goes towards the firewall and dripping on the exhaust manifold. This could honestly be as simple as a Failing Cap. I am running to get a brand new one. I have not pressure tested yet only because my gut believes l have full compression and am chading a simple leak in the system. Process of illumination however if this doesn't cure my ills l will have to go get the test kit next. No options left after this.


A cooling system pressure test has absolutely nothing to do with cylinder compression.

It tests the cooling system for leaks, that's all it does.

The tester also has the equipment to test the radiator cap to see if it's leaking or properly holding pressure.

I have a 2007 300 SRT, there is no coolant overflow cap on these cars only a radiator cap.
It's the exact same setup on my wife's 2006 Charger Daytona.

The overflow when it goes out the radiator cap when too much pressure is built up goes into the reservoir that is molded as part of the plastic tank that has the radiator cap.

The hose going to the back of the engine is a coolant hose and will be under pressure when hot.


Kayse can't keep up at all now. lol
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2854997
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Thank you for this explanation. Ok. So. The cap on the overflow is leaking and running down that line that goes to the back of the firewall. Then dripping onto the manifold and steaming off if that. There is no radiator cap. Only this cap iff the over dlow where the fluid is added. Different system than lve ever has before. But. Feom everything lm reading it sounds like this cap cant leak. It must seal. And then it will allow the system to operate correctly. Is this true

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2855026
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Illuminating

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2855067
12/04/20 02:29 AM
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Originally Posted by KcCrown
Thank you for this explanation. Ok. So. The cap on the overflow is leaking and running down that line that goes to the back of the firewall. Then dripping onto the manifold and steaming off if that. There is no radiator cap. Only this cap iff the over dlow where the fluid is added. Different system than lve ever has before. But. Feom everything lm reading it sounds like this cap cant leak. It must seal. And then it will allow the system to operate correctly. Is this true


There is no cap on the overflow.

There is only a radiator cap on the reservoir.
[Linked Image]

The small black hose in the pic is the overflow hose.

The two nipples at the back of the coolant tank are both on the pressurized side of the coolant tank.
There should be NO LEAKS there.

If there are, there's a problem, either a cracked coolant tank or a cracked or not seated hose.

The one hose that comes out the back of the coolant tank goes back to a t-fitting in the heater hoses.
The t-fitting is usually plastic and could be cracked.
Pic below video link.




IMG_2390.JPG
Last edited by SNK-EYZ; 12/04/20 02:29 AM.

Kayse can't keep up at all now. lol
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2855776
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Yes. This all makes perfect sense to me. Sorry l did use the wrong word. You are 100% right.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2855777
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[15min idoling with cap off.. it is bubbling an air bubble every 30 seconds and steaming a bit.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2855779
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After 18 min idoling and bubbling slowly, it finally opened the thermostat and fluid dripped a bit, l refilled back to full and am watching.
I wonder honestly if l am still just getting trapped air out.

It suddenly pushed coolant up to top of Cap hole and over slowed a touch then dropped back to about normal.
When l turned it off, it over slowed a little and then dropped back to normal. Its warm but not crazy hot.

16072058990652743382641076368490.jpg
Last edited by KcCrown; 12/05/20 06:07 PM.
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2855825
12/05/20 08:30 PM
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I've tried to remember everything I've read; you have always purged with heater on high, right?

And the pressurizers are great because you can really look all around the cooling system closely without fear of burn, steam in your face, etc.

Those reservoirs are actually pretty cheap. I replaced mine with Mopar one just to have a clearer view, and I believe it was about $40.


Facts are stubborn things.
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: larrymopar360] #2855849
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No actually No one said to have the yester on? Every one including the video l watched have the engine cold and off to purge. ?
What does the heater on do??

And, I just went on a test drive. Coolant is literally boiling in the reservoir. wow. Boiling. Crazy. The thermostat stayed perfect on the dash for the ride. And it didnt Steam until l got back and turned the engine off.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: larrymopar360] #2855852
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I dont see any leak from the Reservoir. It honestly seems like l am still purging air from inside. Like it is incredibly stubborn to purge.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: KcCrown] #2855877
12/05/20 11:32 PM
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pull the spark plugs and see if one looks a lot different than the others!!=head gasket


my ladder of success is missing some rungs
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: rhad] #2855883
12/06/20 12:03 AM
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Originally Posted by rhad
pull the spark plugs and see if one looks a lot different than the others!!=head gasket


iagree

Pull one plug from each cylinder and look for signs of coolant.

Bad head gasket symptoms

Quote
White smoke coming from the tailpipe.
BUBBLING IN THE RADIATOR AND COOLANT RESERVOIR.
unexplained coolant loss with no leaks.
Milky white coloration in the oil.
Engine overheating.


Just because it doesn't seem to run bad for now doesn't mean there isn't a head gasket problem.


Kayse can't keep up at all now. lol
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: SNK-EYZ] #2855886
12/06/20 12:13 AM
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You can have a blown headgasket and not have water in the oil.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: stumpy] #2855892
12/06/20 01:25 AM
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You said you drove for a few weeks before the problem started. Air would purge out on it's own long before then.
Did you fix whatever the leak was at the reservoir? If not that can be causing the problem. The reservoir with the rad cap is part of the pressurized system and if it has a leak on that part and not pressurizing properly it can cause problems.
It sounds like you still didn't bother pressure testing the system yet? Without doing that you're wasting a lot of time guessing. Same with checking for other problems people mentioned. Just because parts are new doesn't mean it doesn't have a problem.

Last edited by 5thAve; 12/06/20 01:25 AM.
Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: 5thAve] #2855991
12/06/20 12:51 PM
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iagree

There is air entering the system somewhere. I would pressurize the system with the spark plugs out. With pressure on the system, use a borescope to look into the cylinders. You may see the leak in there. A coolant leak in a cylinder will knock the carbon off and make it look clean/newer than the rest. So note that as well while doing a borescope. It may be external as well. Use some windex or something on the top of the tank where there's no coolant. The windex will bubble where there's air leak. You might not find any leaks either. With the engine cold, it might be fine. When it's hot, it changes the growth of the metal/gaskets, and will leak then. I've pressure tested cylinder heads and are fine when cold. Wen they get to 180°, then they opened a crack. This is what I would do. Take it or leave it.
Like mentioned, new parts aren't always good parts, so don't rely on that to fix a problem. Maybe something wasn't installed correctly? Maybe something has been damaged during all the overheating the engine has encountered lately?

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: 440_Offroader] #2856001
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I worked on a diesel engine that had a small crack in one of the cylinders. The crack would not allow coolant into the cylinder, but would allow hot gases into the coolant passage. The engine could idle for hours without a problem. When the engine was under load (full boost) it would boil the coolant in minutes.

Re: Hemi 5.7 overheating after new thermostat and air purge. [Re: tahoechallenge] #2856225
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Posts: 472
Central NY
You need to test for combustion gasses in the coolant,also does the fan work?

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