Overheating Grand Cherokee 4.0L 1998 - JeepForum.com
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post #1 of 7 Old 05-26-2005, 04:36 AM Thread Starter
Mark Purbrick
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Overheating Grand Cherokee 4.0L 1998

Hopefully someone can help me out with this one......I am currently having problems with an overheating engine.
The coolant level warning light came on within a couple of miles of home so I proceeded watching the temp gauge...it didn't go over normal operating temp.
Next morning I topped up the overflow tank and checked level in rad, then drove a few miles before the coolant warning came on again. This time I called the recovery truck and had the car taken to a local garage.
It transpired that the bottom of the rad was leaking badly so the guy ordered a replacement.
After fitting the new rad the engine was run up but the top of the rad was hot and the lower cold.
The guy then took out the thermostat (which was subsequently found to have failed shut) and ran the engine, rad was then hot on top & bottom hoses.
The car was run for 15-20 mins before it started overheating and the dash board 'check gauges' warning came on, at the same time the overflow tank started to overflow.
Now somewhat confused.....I am hoping that the 'new rad' has a problem so he is returning it as 'defective' and getting another supplier to rebuild my original rad with a bigger core.
Please....please could anyone advise on what the potential problems could be and how to resolve them.
Many thanks, Mark

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post #2 of 7 Old 05-26-2005, 06:37 AM
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The cooling system was probably burping. Depending on how he refilled the system, there are air pockets in the coolant. They make the sensors read like you are overheating and everything overflows for a minute while it pushes the air out. A way I try to avoid this is by refilling the cooling system utilizing the thermostat housing. By filling it up from there, it helps get the engine loaded with coolant first, instead of gravity feeding from the radiator. I still have to top the radiator off, and yes, there's a little air from the upper radiator hose that get's stuck. To help that though, I squeeze the hose after install to move air out and suck coolant in.

See if it continues to do this or if it goes away. One of my trucks burped three times prior to working correctly.

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post #3 of 7 Old 05-26-2005, 08:39 AM
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Also, just to make sure you don't have a cracked head or blown gasket check to see if there is any coolant in your oil. Just to be on the safe side.

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post #4 of 7 Old 06-01-2005, 01:56 AM Thread Starter
Mark Purbrick
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Overheating Grand Cherokee

Hi Guys,

Well the latest news is that I've taken my old rad to a supplier for refurbishment and its due back this afternoon.....it seems that they deal with a lot of GC's.

So as to maximise success in replacement of rad/filling of rad/air purging of the system etc......can anyone please advise on the process to ensure a happy running GC with hopefully no overheating thereafter.

Many thanks......Mark
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post #5 of 7 Old 06-01-2005, 05:32 AM
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Well you have eliminated two of the three vital components of the cooling system. Now check for flow. Remove the Rad cap and start the engine. Watch for the fluid to flow, after the thermostat opens. You can raise the front end. This should force any trapped air to burp out at the Rad cap area.

Cheers Steve

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post #6 of 7 Old 06-01-2005, 07:30 AM Thread Starter
Mark Purbrick
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Overheating Grand Cherokee

Thanks Greasefingers......

The guys plan is to run the engine without the thermostat first and hopefully purge any air from the system....I'll let him know to lift the front of the car up to help this.

We're hoping that the new rad will sort the problem out (everything is crossed). He will then fit a new thermostat as the old one failed shut and hopefully I'll be back on the road again.

Cheers, Mark
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post #7 of 7 Old 05-10-2012, 10:15 AM
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water pump

after replacing radiator,2 thermostats,and fan clutch took water pump out andfound impellor missing. should have checked earliier.1994 grand cherokee laredo 105k miles
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