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5.2 magnum not building coolant pressure## fixed thanks all #2576174
11/09/18 02:03 AM
11/09/18 02:03 AM
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Alabama
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Bama ram Offline OP
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Hey guys please help if you can, 93 5.2 magnum.(Heater core bypass during all the testing) With a radiator pressure gauge I hold 16psi with no drop. Cap tested and pass also.. 2nd water pump in a week I can take heater hose off while running and it pumps water out fine, I can pinch the heater hose and it doesn't affect the top return hose to radiator pressure wise.. block flshed through block drains thermostat opens and trickles out enough to get top tank of radiator hot.. cap on and I don't build pressure and starts to over heat. Would cracked heads do this or can someone please point me in the right direction.. it built pressure one time during testing just long enough to cut truck off, crunk it up and it was gone again

Last edited by Bama ram; 11/11/18 06:23 PM.
Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576195
11/09/18 02:49 AM
11/09/18 02:49 AM
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Lincoln Nebraska
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RapidRobert Offline
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Quote:
cap on and I don't build pressure and starts to over heat.
It is overheating? what temp? confirmed with a good gauge? idling/around town or interstate? More details please.


live every 24 hour block of time like it's your last day on earth
Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576217
11/09/18 03:39 AM
11/09/18 03:39 AM
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Freeport IL USA
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poorboy Offline
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Cracked heads or bad head gaskets that leak into the cooling system tend to build more pressure in the cooling system, not lower the pressure.

Are you sure you have the serpentine belt running around the water pump pulley the correct direction? I've seen the belt routed around the water pump the wrong direction and that causes all kinds of problems.

What does "thermostat opens and trickles out enough to get top tank of radiator hot,,cap on and I don't build pressure and it starts to over heat" mean?

How do you know the cooling system is not building pressure? Do you have a pressure gauge on the cooling system someplace?

How hot is it really getting? Do you have a known good temperature gauge on it?

Is the radiator plugged, or partially plugged? Are you loosing coolant? A system that holds a consistent 16 lbs of pressure with a pump that has no sign of a leak should be pretty sound. Gene

Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576228
11/09/18 05:31 AM
11/09/18 05:31 AM
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in a cattle trailer down by th...
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Guitar Jones Offline
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Radiator is partially plugged. Went through this many times.


I never learned to count my blessings, I choose instead to live inside my disasters.

The Scamp is sold, now just two old trucks and one new one.
'92 D250 Club Cab CTD, 47RH conversion, pump tweaks, injectors, rear disc and hydroboost conversion.
'74 W200 Crew Cab 360, NP435, D44, D60 and NP205 divorced transfer case. Magnum 5.2 MPI and NV4500 coming soon.
2019 1500 Long Horn Crew Cab 4WD, 5.7 Hemi!
Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576253
11/09/18 10:57 AM
11/09/18 10:57 AM
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Alabama
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Bama ram Offline OP
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Alabama
With the thermostat open their is suppose to be a good amount of force/pressure that pushes the engine coolant out of the block to the radiator to cool it down. That's what I'm not getting. The radiator is fine it works. I'm not getting the water back out of the block so it can cool down.. I can drive for an hour and open the radiator cap and not get sprayed. That's the "pressure" I don't have

Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576269
11/09/18 11:51 AM
11/09/18 11:51 AM
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Chicago
PurpleBeeper Offline
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My gut instinct is that your radiator cap is bad, even though it tested good...or maybe just not sealing well on the radiator fill neck. It certainly would explain a lack of pressure in the system + your overheating.


70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"
Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576624
11/10/18 01:18 AM
11/10/18 01:18 AM
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Freeport IL USA
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poorboy Offline
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My gut instinct is that you have the serpentine belt running on the pulleys the wrong way (or you have the wrong water pump) and you are turning the water pump backwards. Did the problem start after someone changed the 1st water pump, or maybe after someone changed the serpentine belt? Those belts have to go around the pulleys in the correct direction for everything to function correctly. Gene

Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576627
11/10/18 01:29 AM
11/10/18 01:29 AM
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Conroe , Texas
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iapco103 Offline
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Lack of pressure in the cooling system is not the problem, Lack of water circulation IS the problem.
Focus on that.

The suggestion about belt routing is a good one , it is all too easy with a serpentine belt to route it wrong and think its right. Paul

Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576766
11/10/18 01:57 PM
11/10/18 01:57 PM
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St Louis, MO 63026
convx4 Offline
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Could have the wrong water pump. The wrong pump for the wrong application causes issues like your having. Could be wrong with the following: LA water pumps are clockwise rotation. Magnum are counter clockwise.

Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576770
11/10/18 02:01 PM
11/10/18 02:01 PM
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Every Magnum water pump I have seen comes with the pulley attached, not to mention they look way different and the LA pump is longer. Probably not an LA pump.


They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2576879
11/10/18 08:45 PM
11/10/18 08:45 PM
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Badham Co.
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Y3 70 BEE Offline
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Sure you dont have a partial pressure radiator cap?

Re: 5.2 magnum not building coolant pressure [Re: Y3 70 BEE] #2576931
11/10/18 10:46 PM
11/10/18 10:46 PM
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Posts: 14,818
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Supercuda Offline
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Originally Posted By Y3 70 BEE
Sure you dont have a partial pressure radiator cap?


that jogged a memory cell, so I dug it up,

http://www.allpar.com/fix/engines/cooling-caps.html


They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
Re: 5.2 magnum not building coolant pressure [Re: Supercuda] #2576943
11/10/18 11:05 PM
11/10/18 11:05 PM
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Lincoln Nebraska
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RapidRobert Offline
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Supercuda, good read/info, thank you!


live every 24 hour block of time like it's your last day on earth
Re: 5.2 magnum not building coolant pressure [Re: Supercuda] #2576987
11/11/18 01:28 AM
11/11/18 01:28 AM
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Atlanta, GA
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Early style 5.2/5.9 magnum pumps had a bolt on pulley.

Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2577036
11/11/18 08:36 AM
11/11/18 08:36 AM
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Guitar Jones Offline
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All the magnums have the fixed pulley with the single nut fan clutch. Only the 91 318 Dakota had a bolt on pulley with the serpentine belt.

So let's recap, water pump replaced, pushes water out the heater hose so it's moving water. Tstat opens, cap tests good and it holds pressure. Block has been flushed out. Hmm, radiator is still partially plugged whether he wants to believe it or not.


I never learned to count my blessings, I choose instead to live inside my disasters.

The Scamp is sold, now just two old trucks and one new one.
'92 D250 Club Cab CTD, 47RH conversion, pump tweaks, injectors, rear disc and hydroboost conversion.
'74 W200 Crew Cab 360, NP435, D44, D60 and NP205 divorced transfer case. Magnum 5.2 MPI and NV4500 coming soon.
2019 1500 Long Horn Crew Cab 4WD, 5.7 Hemi!
Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2577195
11/11/18 06:24 PM
11/11/18 06:24 PM
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Posts: 3
Alabama
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Bama ram Offline OP
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Alabama
Hey guys thanks for all your help help and suggested reading material. It was in fact the radiator cap, I ran down to the Dodge dealer and got one of their 15$ caps and it might be the only place I'll be buying caps from here on out. Sorry for the long wait I had water inside my computer causing it to pulsate the ground for the sensors and it wouldn't crank up which drove me crazy trying to troubleshoot a no start. You guys aren't so bad I'm going to have to stick around and check out what this site has to offer

Re: 5.2 magnum not building coolant pressure [Re: Bama ram] #2577269
11/11/18 09:42 PM
11/11/18 09:42 PM
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Lincoln Nebraska
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RapidRobert Offline
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Quote:
You guys aren't so bad I'm going to have to stick around and check out what this site has to offer
You just caught us on a good day (fasten your seat belt), you'll see!


live every 24 hour block of time like it's your last day on earth
Re: 5.2 magnum not building coolant pressure [Re: RapidRobert] #2577493
11/12/18 02:29 PM
11/12/18 02:29 PM
Joined: Sep 2003
Posts: 10,566
north of coder
moparx Offline
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Originally Posted By RapidRobert
Quote:
You guys aren't so bad I'm going to have to stick around and check out what this site has to offer
You just caught us on a good day (fasten your seat belt), you'll see!


like my old man usta say : "it's all good. just some gooder than others!" biggrin
beer


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