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jsouza111 06-21-2011 10:18 AM

Heating Problem!!
 
hi guys. i have a 99 grand cherokee 4.0. jus wondering wat u guys think could be my problem.. my truck tends to go ova the heat temp of 210 if its fully warmed then i shut it off to run into a store and then start it back up it begins to go ova the 210 and one time n started to shake on me while i was pullin off. but if i pull away rite away it slowly goes down to 210..HELP!!!

Frango100 06-21-2011 12:46 PM

Re: Heating Problem!!
 
I would start by checking the cooling liquid level first. Which kind of cooling fan do you have, the electrical one or the viscous coupling one driven directly by the engine? The cooling fan could be inop.

JeepMe 06-21-2011 12:47 PM

Re: Heating Problem!!
 
Not sure exactly what you're saying, but I'll try to make sense of it.

Are you saying that your Jeep overheats when you drive it, but then cools off when you pull over?

The first thing I would check is if the fan is coming on or not and coolant levels. If it's not, it's most likely the relay (located under the passenger headlight). Is there enough coolant? If so, then I would look at the thermostat and water pump.

jsouza111 06-21-2011 04:33 PM

Re: Heating Problem!!
 
Frango100

thx for the help.. i got the viscous coupling one driven directly by the engine lol


JeepMe

but yae na it dont overheat while i drive... say if i went from point a to point b the truck will be warmed at 210.. now if i shut it off n run into a store or suttin and turn it back on and drive away it will slowly creep past the 210 then go back to 210.. one time when i didnt pull off rite away it started to do a lil shake on me untill i pull down the street ... thx for ur help to

Frango100 06-21-2011 05:39 PM

Re: Heating Problem!!
 
It can be that the viscous coupling is bad and wonīt drive the fan (enough). The next time you see the temperature rise, have a look if the fan is running.
And just to put the things straight, you donīt have a heating problem, but a cooling problem.:lol:
If the fan seems to be running ok (producing a lot of airflow, take care with the hands and loose clothing), it is maybe time for a cooling system flush, a new thermostat and fresh liquid.

2004wjmedic 06-21-2011 06:59 PM

Re: Heating Problem!!
 
Are you saying that your temperature gauge goes up if you turn off the engine for a few minutes and then start it back up after it already being at the normal operating temp? If so it could be because when the engine is off the coolant is not being circulated around and when you start it up again the coolant is circulated again and thus cooled down by the radiator.

I have the 4.7 and my Jeep will do the same thing on a hot summer day but always cools right back down and never has an issue.

jsouza111 06-21-2011 08:16 PM

Re: Heating Problem!!
 
thx frango will check..

2004wjmedic

yae thats wat im sayin... but see one time when i started it up n pulled out of my driveway n had to wait in traffic before i could get it above say like 10 mph it started to do like a death shake and it worried me... thx for the help

2004wjmedic 06-21-2011 08:33 PM

Re: Heating Problem!!
 
My dad has a 99 WJ with the 4.0 and his does that occasionally.

JeepMe 06-21-2011 08:34 PM

Re: Heating Problem!!
 
Quote:

Originally Posted by 2004wjmedic (Post 435279)
Are you saying that your temperature gauge goes up if you turn off the engine for a few minutes and then start it back up after it already being at the normal operating temp? If so it could be because when the engine is off the coolant is not being circulated around and when you start it up again the coolant is circulated again and thus cooled down by the radiator.

I have the 4.7 and my Jeep will do the same thing on a hot summer day but always cools right back down and never has an issue.

Yeah, that' exactly what happens and is normal. Basically, the head is cooled by the coolant that is [more or less] continually circulated when the engine is on. When you turn the engine off, the water pump is no longer turning. This means all the heat from the heat will dump into the coolant that's around it. Your temp gauge will read this and register hot.

When you start your engine, the water pump should turn and circulate the coolant. This will cause the cooler coolant to enter the head and the temp gauge will drop to normal. If the gauge doesn't cool down quickly, you most likely have a problem with your water pump (not circulating the coolant properly). Or maybe a thermostat (but pump would be my primary guess).

Frango100 06-22-2011 03:00 AM

Re: Heating Problem!!
 
If you have a problem or not all depends on until how high the temperature rises. After switching off the engine the water pump stops, but also the combustion. There is some residual heat from the heads and the heat sink effect that will be absorbed by the cooling liquid. As soon as you start the engine again, there can be a slightly higher then normal temperature indication, but that should go down quickly. When the Jeep is standing still and the temperature will rise significantly, you probably have a problem with your cooling fan. If the waterpump would be bad, you also would expect problems during driving.

2004wjmedic 06-22-2011 10:29 AM

Re: Heating Problem!!
 
If it were the waterpump I believe it would be a little easier to figure out than the fan. I know my waterpump went out in February and I got all kinds of warning lights and the temperature gauge spiked. When my dad's wj's cooling fan went out the temperature would go up significantly when sitting in traffic but then start to come down again when underway again.

JeepMe 06-22-2011 12:40 PM

Re: Heating Problem!!
 
Quote:

Originally Posted by 2004wjmedic (Post 435678)
If it were the waterpump I believe it would be a little easier to figure out than the fan. I know my waterpump went out in February and I got all kinds of warning lights and the temperature gauge spiked. When my dad's wj's cooling fan went out the temperature would go up significantly when sitting in traffic but then start to come down again when underway again.

Water pumps can fail drastically (like yours) or be minor failures. Sometimes the shaft gets loose, causes the impeller to scrape the housing, and then won't provide proper flow. Causes vehicles to overheat at idle (when there's very minimal flow) but not when driving (when it's spinning faster). I've had that happen before. On my 66 Mustang I've also had the pump completely bind up and throw the fan through the radiator.


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