Overheating... head gasket??

[JeepDude04]

Okay, I had some problems with my 1987 Jeep Cherokee Laredo 4x4 overheating this past summer. The temp would climb while sitting at a traffic light. Problem was sourced to be a bad radiator fan clutch... replaced it and fixed the problem. Then, I had issues with it running hot again this fall.. I replaced the thermostat and the problem was fixed.

Now, my car is running hot AGAIN! This time I think it's more serious. Car starts and runs fine, but if you drive it or run motor for more than 10 minutes, the car starts running hot, overpressurizing the upper cooling system and boils over the fluid.

So, I'll give the run down... due to this problem, I've had the equivalent of 3 complete flushes with new Sierra coolant and distilled water... the radiator appears in good shape and keep in mind I have the "high capacity cooling system", I've got ANOTHER new thermoststat in there (figured I'd replace it again and see what happened... didn't fix it), a relatively new fan clutch, a new expansion tank and cap, and many new upper cooling hoses and hose clamps.

So, I'm a wits end... What do you experts think is the problem? I don't think it has anything to do with the radiator as it starts overpressirizing the expansion tank and boils the fluid before the temp guage gets to 195 and therefore, before the thermostat opens and lets coolant to the radiator. Oh, I've also tested my water pump and it is working. My friend thinks it is due to a blown head gasket and somehow exhaust or heat from combustion is leaking out into the water and overheating/overpressurizing the cooling system.

I wanted to run the symptoms by the list before I went out and bought a head gasket kit and start pulling the head.

What do y'all think??? Anything I'm missing here?

Any help appreciated.

Dan Hussey
'87 Jeep Cherokee 4x4 (factory "Off-Road Package")
'89 Porsche 944 S2 (Baltic Blue/Linen)
Seattle, WA

 

[sjx40250]

Dan,
Sounds really familiar! 'Bin there done that. You didn't say how many miles on the Rad. I would pull it and have it cored. I found that mine was 30% plugged even after flushing. Replace hoses. Test the water for HC (rad shop) indicating head gasket leak.

I finally got mine under control a few weeks ago when I installed a MAP adjuster and richend the A/F ratio. But I think my real problem is that I have over 166K miles on the injectors!

 

[NCSUcherokee]

check the color of the oil, if it is milky then you probly have a problem with the head gasket, if not look somwhere else.

since you said you had previous problems with the cooling system, and you recently did work on it, are you sure that it was burped corectly? this happend to me, the system was not burped completely which caused it to over boil which made me loose more coolant which made the problem worse ect. untill i burped it out.

 

[JeepDude04]

Okay... my Jeep has like 202K miles on it. It's old, but in excellent shape and still runs strong, and finding another 5 speed Cherokee like this with the factory off-road package would be tough. Basically... I love my Jeep, so I want to get it fixed and keep it!

Anyways... I would think it was the radiator, pull it out and have it re-cored, but the car is overheating before the thermostat is even opening! So, I don't think this is my problem?? Any other ideas???

Thanks on the "burping suggestion"... You may be onto something... I remember hearing a gurgling sound down by the heater core just before having this problem (like maybe there was air in there).

Anyways, how do I properly "burp" the system?? All I know is I'm not overheating in the sense of the term that I think you and I know... It's like MEGA-OVERPRESSURIZING the upper part of the cooling system... like crazy high pressure and blowing coolant out past the cap when it's on! Really bad!

Someone has to have had this happen before. According to my friend, there are two ways a head gasket can go. It can let coolant into the oil (my oil looks fine), or it can let combustion into the coolant getting it VERY hot! This would explain why the coolant is getting so hot before the engine really gets that high in temp.

Any ideas? I need to figure this out soon so I can order the appropriate parts and get my Jeep back on the road. I'm having to drive my Porsche every day now.... and with our 70 degree sunny days here in Seattle, you can imagine how afull this must be! ;^)

Thanks,
Dan Hussey
'87 Jeep Cheroke Laredo 4x4 (aka "Ski Bitch")
5 speed, factory Off-Road package, Bilstiens

 

[Glenn B]

Damn Dan. Suffering by "having" to drive your Porsche? LOL.... the weather has been nice though lately.

I suggest taking it to a shop and having them do a block test. All the posts about "milky oil" etc.. are nice, but you need to check other things. Might cost ya $45-70 but worth it.... IMHO. Better to go in with as much info as possible.
Glenn

 

[5-90]

If there is an air bubble in the system (closed Renix system,) it will collect behind the thermostat and prevent its opening, thus preventing the flow of coolant. This is why I so often advise the drilling of a pair of 1/16" holes in the thermostat flange and making sure they are mounted at 12:00 and 6:00, which will make the system self-burping (the air will flow thru the top hole, and the water flow from the lower hole will compensate. It's a simple solution to a simple problem, which can have very complex consequences.

Since you are overheating, you will need to change your thermostat anyhow (always assume it's wrecked the first time you overheat, and they're cheap anyhow.)

Considering the low basic compression of the 4.0, I'd think it unlikely that you've lost the head gasket so soon. Drill and replace the thermostat. The system will burp itself with about 20 minutes of runtime.

5-90