94 Grand Cherokee Heats up fast

TFWFXDR

MEMBER
1994 JEEP CHEROKEE

I purchased a 94 Grand Cherokee w/ the 4.0L engine. If the vehicle is started in the morning (sitting all night) almost instantly there is a lot of heat under the hood. It will then run about 200 degrees. I flushed the coolant system. Didn't see anything abnormal but still no help. I removed the thermostat, now it runs about 180. It had an bad muffler so I thought maybe a backed up convertor was casuing the heat. I took it in and had everything new installed from the tail pipe to the exhaust manifold. Thought it might be a water pump or radiator, but the engine compartment will get too hot to touch within a couple minutes. Seems like either a water pump or radiator would take longer. Not to mention it still does not have a stat installed. Could it be an exhaust mainfold? The one on the Jeep looks good, can't see any holes and don't smell exhaust? First jeep I've ever owned, not sure if there is something typical or expected for this model.

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Try bleeding the air out of the cooling system and see whether it helps, also at night time start it up and look at the exhaust manifold is it glowing.

Last the fan clutch could be slipping-that's if it has one.

Running it w/o the Stat is not a good idea, the computer needs the correct temperature from the coolant temperature sensor to fine tune the A/F mix.

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Wednesday, September 5th, 2007 AT 4:50 PM

TFWFXDR

MEMBER
2 POSTS

Try bleeding the air out of the cooling system and see whether it helps, also at night time start it up and look at the exhaust manifold is it glowing.

Last the fan clutch could be slipping-that's if it has one.

Running it w/o the Stat is not a good idea, the computer needs the correct temperature from the coolant temperature sensor to fine tune the A/F mix.[/Quote:1de080eca0]

I checked the exhaust manifold last night, no glowing. I forgot to mention I already changed the clutch. That was the my first thought also. If it was a radiator or water pump, would the engine get that hot that fast? I only removed the stat to see if it would take longer to heat up. Which it should. Makes me lean towards a bad pump, but I still don't understand why the engine gets so hot so fast. Thanks for anything you can add!

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Thursday, September 6th, 2007 AT 1:28 PM

RASMATAZ

MECHANIC
75,992 POSTS

Try bleeding the air out of the cooling system and see whether it helps, also at night time start it up and look at the exhaust manifold is it glowing.

Last the fan clutch could be slipping-that's if it has one.

Running it w/o the Stat is not a good idea, the computer needs the correct temperature from the coolant temperature sensor to fine tune the A/F mix.[/Quote:a5e66a3439]

I checked the exhaust manifold last night, no glowing. I forgot to mention I already changed the clutch. That was the my first thought also. If it was a radiator or water pump, would the engine get that hot that fast? I only removed the stat to see if it would take longer to heat up. Which it should. Makes me lean towards a bad pump, but I still don't understand why the engine gets so hot so fast. Thanks for anything you can add![/Quote:a5e66a3439]

All it takes is 5 mins. For an engine to overheat stationary. Sounds like circulation problem- Remove the cap fill it to the brink don't put the cap back on, now start it up-is the coolant swirling around. Now squeeze the upper hose for a few secs-let go -did the flow increases-

Check the radiator fins it should be evenly warm across-they shouldn't be any cold spot.

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Thursday, September 6th, 2007 AT 3:30 PM