Moparts

5.2 magnum not building coolant pressure## fixed thanks all

Posted By: Bama ram

5.2 magnum not building coolant pressure## fixed thanks all - 11/09/18 06:03 AM

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
Posted By: RapidRobert

Re: 5.2 magnum not building coolant pressure - 11/09/18 06:49 AM

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.
Posted By: poorboy

Re: 5.2 magnum not building coolant pressure - 11/09/18 07:39 AM

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
Posted By: Guitar Jones

Re: 5.2 magnum not building coolant pressure - 11/09/18 09:31 AM

Radiator is partially plugged. Went through this many times.
Posted By: Bama ram

Re: 5.2 magnum not building coolant pressure - 11/09/18 02:57 PM

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
Posted By: PurpleBeeper

Re: 5.2 magnum not building coolant pressure - 11/09/18 03:51 PM

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.
Posted By: poorboy

Re: 5.2 magnum not building coolant pressure - 11/10/18 05:18 AM

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
Posted By: iapco103

Re: 5.2 magnum not building coolant pressure - 11/10/18 05:29 AM

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
Posted By: convx4

Re: 5.2 magnum not building coolant pressure - 11/10/18 05:57 PM

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.
Posted By: Supercuda

Re: 5.2 magnum not building coolant pressure - 11/10/18 06:01 PM

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.
Posted By: Y3 70 BEE

Re: 5.2 magnum not building coolant pressure - 11/11/18 12:45 AM

Sure you dont have a partial pressure radiator cap?
Posted By: Supercuda

Re: 5.2 magnum not building coolant pressure - 11/11/18 02:46 AM

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
Posted By: RapidRobert

Re: 5.2 magnum not building coolant pressure - 11/11/18 03:05 AM

Supercuda, good read/info, thank you!
Posted By: mgoblue9798

Re: 5.2 magnum not building coolant pressure - 11/11/18 05:28 AM

Early style 5.2/5.9 magnum pumps had a bolt on pulley.
Posted By: Guitar Jones

Re: 5.2 magnum not building coolant pressure - 11/11/18 12:36 PM

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.
Posted By: Bama ram

Re: 5.2 magnum not building coolant pressure - 11/11/18 10:24 PM

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
Posted By: RapidRobert

Re: 5.2 magnum not building coolant pressure - 11/12/18 01:42 AM

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!
Posted By: moparx

Re: 5.2 magnum not building coolant pressure - 11/12/18 06:29 PM

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
© 2024 Moparts Forums