i have a 99 limited 4.0L 2wd
The coolant is going to the over flow bottle and just coming out the top.
i have noticed that it seems like the system has a lot of pressure building up on the hoses. this thing has a remand WP and a new radiator so any help would be great.when it goes into the overflow it is as soon as the therm. opens as when it is started it is fine. it does bubble when going in to the over flow. i just did the head and put a 97 head (0631) on as the old 1 was cracked. i pull the code p0118 most of the time when starting but the temp ect sensor is working fine. i also replaced the tps as there was a code for it.
also the top hose gets hot before the bottom and thats just not right... right?

 

If you have bubbles while the engine is running and excessive pressure building up, that's a sign of a bad head gasket, cracked head or other breech between cylinder(s) and a water jacket. Get a cooling system pressure tester and see if the system holds.

 

the thing is that it only does it after the therm. opens and not before.
if that where the case wouldnt it do it from the start?

 

Have you tried replacing your radiator cap? Sounds like maybe it's stuck and constantly allowing all that pressure and coolant back into your overflow bottle when you get up to temp.

 

i was going to do that but the hoses are really hard and there is alot of pressure thats why i dont think it is the cap. and besides, its new before i bought the jeep 1 month ago.
what are the chances that it could be the head i pull in the JY?
it looked fine on the surface and it was on a jeep that was wreaked not just scraped.
could it be a cracked block?

 

You probably should have had that head shaved at a machine shop before installing! A head from a JY is risky business to me...you never know how that Jeep might have ended up there in the first place, could have been a blown engine/head and the PO just didn't want to deal with it.

 

i said it came off a wreaked jeep and i had a flat edge to test it. it was good

 

If you replaced the head gasket it could still have issues.

Radiators don't typically cause over pressurization.

Like previously said...its usually the combustion chamber adding the extra pressure.

Logically the HG is in question...

 

Also keep in mind that coolant expands as its heated.

Maybe its coincidence that the tstat opens when this happens. Maybe its because the tstat opens at that certain temp, and the pressure is still building as the temp climbs...

Lots of things to check into.

 

Could have very well been a stolen recovery. Borrow a cooling system pressure tester and see whats up, just guessing gets expensive after a while.

 

i went to auto school and i finally got a hold of him and he confirmed its the head so im going to have to buy another head but thanks for the help everyone and ill keep updating.

 

just got another JY head and sent it to the Machine Shop (MS) and it had no cracks but was twisted so had it skimmed. all and all $80 later it is ready for me to reseat the valves.

ill keep updating

 

Good luck!

 

Thanks for keeping us posted!

 

well got it all back together today and im having the same prob.
i think it might be the block.
and before u all start saying that is a 1;1000000 chance, i know but it has to be.

has anyone had a bad block?