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Overheating mystery

Overheating mystery

Homerhammer

Jeeper
Posts
2
Thanks
0
Location
Austin, Tx
Vehicle(s)
1985 CJ7 4.2L v6 258cu in.
85 jeep CJ7 inline v6 AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l
Installed new exhaust manifold due to exhaust leak, installed new water pump because it moved fan up and down when revving engine, guess bearings going out. Installed new radiator. Installed new thermostat. But now it is overheating after driving about a mile or two. My guess is that I was sold a defective water pump or thermostat, or possibly radiator. A mechanic I know said it appeared to be getting water flow thru engine because hoses were hot. You can see pressure build up when it is running with radiator cap off. Mechanic thinks it could be bad engine gasket, causing pressure to build up. I think bad thermostat. Question - What causes pressure to build up and not circulate, bad thermostat or bad engine gasket or something else.
 
Thermostat
 
WELCOME :chug:
There are 2 water pumps for our year Jeep.
One for serpentine belt(reverse rotation WP)and then one for 'V' belt('normal' rotation).
You may well have either the wrong rotation WP install'd or it was a mis-boxed WP that show'd the correct part number.
You need to compare impellers between what you took out to what you have now.
Also, did you 'burp' the cooling system for trap'd air?
Is the t'stat installed correctly with the temp node in the block?
BTW: What in hell is an 'engine gasket'????
LG
 
My first thought was burping the air as well. If you haven't done it, do that first. And when you start to run the engine cold, does it warm up normally and then stop at an appropriate temp first or just keep climbing ? I am wondering if the thermostat is opening at all. You can test it by pulling it and dropping it in water hot enough to trigger it. Again, an easy/cheap test.

Good luck. Overheating sucks.
 
I haven't replaced my thermostat in a while and I can't remember if it's possible, but could it be facing the wrong direction?

-Jon
 
Had to change my Homerhammer user name and email because I was unable to log back in and password reset not working; IT must be doing upgrades this weekend.
Thanks for replies. I think it is the wrong water pump (for serpentine belt, mine is v-belt) and the impeller blades are opposite direction. Trying to contact mechanic who did that part of work to see if he checked impeller direction. He did mention that the new pump had a larger size outlet for the heater hose and he put on larger hose. Do serpentine WPump have larger diameter outlet for heater hose?

I replaced thermostat and will test that tomorrow when I have more time. Did not see word Reverse on parts of pump I could see.

Meant to say Mechanic said head gasket problem could cause pressure build up, although there are no problems occurring related to blown head gasket.
 
The reverse water pump sounds like THE problem. If not my first thought is, turn the thermostat over. By the way you can't have an inline V6. :) you either have an inline engine or a "V" engine.
 
When was the last time you had a full 'rod-out' done on the radiator and a engine block flush?
LG
 

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