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-   -   high pressure in cooling system hours after shutdown (http://www.jeepgarage.org/f203/high-pressure-in-cooling-system-hours-after-shutdown-67023.html)

MN_wjLIMITED 10-23-2013 06:49 AM

high pressure in cooling system hours after shutdown
 
The local dealer told me a faulty t-stat although heat works great can cause pressure build up, im no dummy but is this true? 99 wj 4.7

Frango100 10-23-2013 08:54 AM

Re: high pressure in cooling system hours after shutdown
 
That sounds strange. A failed open thermostat would cause low coolant temps and a failed closed thermostat overheating. Also the radiator cap would relief pressures over 18 PSI. As soon as the engine cools down, the coolant volume reduces and an underpressure should draw back coolant from the overflow reservoir. So can it be that the radiator cap doesn't open and causes too high pressure which takes longer to reduce?

MN_wjLIMITED 10-25-2013 01:03 AM

I have no clue, replaced the cap a couple weeks ago but no good result. Just replaced temp sensor and Im going to bite the bullit and do the t-stat in the morning and go from there.... and I tested the e fan and it works but isnt kicking on so im going ti checj the NEW relay and wiring out and see what the hell is going on.

hoffmanestates 10-25-2013 08:56 PM

Does head gasket cause psi?

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Frango100 10-25-2013 09:14 PM

Re: high pressure in cooling system hours after shutdown
 
Quote:

Originally Posted by hoffmanestates (Post 917549)
Does head gasket cause psi?

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A leaking headgasket could cause gasses to go into the coolant, or coolant into the cylinder or into the oil. But the pressure should not get higher, because the radiator cap will release the pressure when it goes over 18 PSI.

MN_wjLIMITED 10-25-2013 09:14 PM

Im sure it does but ive pressure tested the system twice with no bad results

Frango100 10-25-2013 09:21 PM

Re: high pressure in cooling system hours after shutdown
 
Did you change the t-stat this morning?

MN_wjLIMITED 10-25-2013 09:37 PM

No, working overnights finally got to me... waiting for it to warm up a bit I passed out on the couch and woke up just in time to go to job 2


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