ADNC

First let me start by saying HI. I have a 98 Cherokee 4.0 and it just began to overheat so i am looking for advice. I did a little digging but wanted to see what you guys think.

To start, about a month ago i put some radiator stop leak in the system to stop a leaking heater core, and it worked like a charm, no more greesy mist on the windshield. everything since then has been fine until today i went to pick up my sister's kids at the bus stop.

While the car sat at idle the temp rose to 210 but i noticed the air coming out of the vents was cold...about 5 minutes later the heat came in nice and hot. after about 5 minutes of that the temp (quickly) rose to redline and the check gauges light came on. i shut down the car and let her sit for about 10 minutes and she started right back up and went to 210 and i drove off.

When i got back to the house and parked it shot back up.

The fan is running.
I DO have heat.
The resivour is filled (i mean filled to the brim).

I am guessing the thermostat but i have been wrong before..thanks in advanced for the help

ZINGGG

With the rapid change in temperature like that, thermostat is definitely a suspect. In the future, do not use a product like stop leak. Although it might stop the leak, it tends to clog up the few cooling system components, which it sounds like finally happened. Drain all the coolant by taking off the lower radiator hose (where it connects to the radiator), do a flush of the system, and start replacing components. I'd start with the thermostat and water pump (if it hasn't been replaced in a long time), as well as flushing the radiator (hopefully that will help even though there's a chance you clogged it putting stop leak in it. Also, bite the bullet and put in a new heater core. Stay away from stop leak in the future!!

Sideways99

id say thermostat
also since you mentioned bars leak, run a flush through your system to clear out the extra gunk, leaving that float around in your cooling system too long is not the best thing for it.
nor is it a permanent soulution, kinda like a t-case drop it more bandaid than full on fix

Sideways99

you beat me to it

djb383

The proper way to "fill" the cooling system is (motor COLD) remove the rad cap and fill the radiator to the brim. The reservoir should NEVER be filled to the brim.....but rather somewhere between the 2 marks on the side of the bottle.

tjwalker

1. What is the history of routine cooling system maintenance? IE; when was the last time the coolant was changed?

2. How old are all other cooling system components? Radiator, water pump, thermostat, radiator cap?

3. Like the others, I'm not a big fan of stop leak products. It can help, but it has "side effects" and that includes clogging of the cooling system.

4. You may want to start with a flush/fill, a new 195 degree MOPAR thermostat and a new radiator cap and see where you are at after that. You may eventually have to pull that heater core out if it begins to leak again. Not a fun job, but don't use any more stop leak.

ADNC

I wanted to do a heater core, bought one and everything...figuring the worst thing it could do (in a short period of time) would be not work resulting in a heater core replacement and coolant flush anyways. not my finest moment, but it worked.

I did wounder about excess stop-leak, i did find it concerning that a product could stop leaks yet be safe to stay in a cooling system

The coolant botle was filled to the "fill" bar on the side when the Jeep runs properly, I found it odd that it had an excess in the bottle thats why i mentioned it, more to aid in diagnosis.

the coolant was flushed about two years ago (although the jeep sat all last year) when i started driving it again the coolant was green and tested good at the oil change place. As far as i know the cooling system is original.

I agree that the car is probably overdue for a thermostat, i will probably due a water pump as i will due a full flush and there is no point doing it twice.. This is actually my wife's Jeep, it is in great condition 171K with a two year old rebuilt trans, it sat because the cat was clogged and i finally got the money to fix it right, so far i added a cat-back, hi-flow cat, K&N Panel, new battery, starter, undercoating...it figures the cooling system would be next..lol

Anyways thanks for the advice guys i'll get to it this week end

ZINGGG

Man, if the cooling system is all original at 171k, it's definitely time for an overhaul. In all honesty, if you're in there already with it drained and you're replacing one component, I'd do all of em, especially at that amount of miles. It's great assurance cause you'll never know when something else is going to crap out on you

freegdr

over heating at idle clutch fan should be checked