Hello all, I have a 1990 Cherokee 4.0. It's runs hot, if I let it idle it runs cool, and if I'm driving on flat ground its fine, as soon as I hit a hill it slowly climbs. Even if its parked in the driveway, an I hold rpms at 2500 in park it slowly climbs to the red. As soon as I let it idle, it cools down. Now I have brand new aluminum 2 core radiator, second radiator I have installed. Brand new t stat, waterpump 2nd water pump. All new hoses, new sending unit. Even did a block test, came back clean. And it is converted to open system.
I really hate to start a new thread, but this has me stumped and I am a mechanic. And I have checked temps with a oinfared gun, and it is getting hot. And one more thing, it seems to be getting worse, I use to be able to drive up hills if it was 70 degrees outside, and it would be fine. Now I just took it out Sunday morning it was cool outside, and it got hot, not to the red, but would have if I didn't pull over. O and it is converted to 2 electric fans, and yes there on.
Thankyou.

 

Are you sure you have the correct waterpump, is the belt routed correctly?

 

Yes, I even took the wp back off this weekend to confirm it was turning the right way.

 

Have you done a compression or cooling system pressure test?

 

Have you burped the radiator?

Raise the front end, with the cap off let the motor get up to temp. You Could have a large amount of air in your engine. And are you electric fans pulling air in the correct direction?

 

Rock, I have burped it so many times its ridiculous. Lol

 

Turbo, I have not done a coolant pressure test, but have done a block test. I have done a compression test, and 3 cylinders were at 40#. Now in all the years I have been working on cars, I have never seen low compression cause this problem. Another wierd thing is that it takes 90# for a cylinder to fire. And it runs like a top and just passed comifornia smog. But I will say, I am starting to think that is my problem.

 

Have you checked your bottom hose? Could you be getting vacuum effect pinching off your lower hose not allowing coolant to pass freely?

 

I put a brand new hose, with new spring it 2 weeks ago.

 

Any other advice?

 

pressure test it

 

Ac condenser clog maybe? . Never hurts to check if u put in the thermostat in correctly. Sometimes it might limit the amount of coolant flow. Umm right coolant/ water mix? . Just throwing stuff out there maybe u didn't check lol

 

Also, no mention of a new fan clutch. Has it been inspected/replaced yet?

 

Mati I have triple checked all of that. Sthon it is converted to dual electric fans.

 

Go back to stock setup