Jeep Garage  - Jeep Forum

Jeep Garage - Jeep Forum (
-   Troubleshooting/Problems (
-   -   ANOTHER overheating WJ (

R0CKKR4WL3R 07-03-2013 09:48 PM

ANOTHER overheating WJ
Did a search of the site and read almost all of everyone else's problems. Found some to be very informative and others could have been, but the thread stops with someone's insight, but no fix or remedy. Your idea sounded good, but "how"?

So on to my jeep...'01 Grand Cherokee Laredo 4.0 with 250,000 miles. Cooling fan is engaged ALL the time. Even when off, I need to remove the fuse or disconnect the fan plug. Up until today, the temp gage USED to read correctly. I found at 210-degrees, the radiator cracked and puked coolant all over the ground without warning. I was actually quite happy until that moment, that it was running great aside from the fan issue. This is the THIRD radiator in a month that I've had to install. Every day it has exploded, the temperature outdoors was 86-92 degrees and humid. Thus making me VERY unhappy!

The radiator, cooling fan, and waterpump were replaced before I bought it. I've had it a year and a half and now I'm at the mercy of the cooling system.
So far I've replaced the cooling fan once, the fan relay 8 times with some working fine and dying, others keeping the fan on all the time, and some not turning it on at all.
As I stated, the radiator has been replace 3 times (not by choice), and the thermostat replaced once.
The heater core is BRAND NEW, from Mopar.
At this point I'm about to replace the waterpump...again, and the Temperature control sensor.
I'm just trying to have a NORMAL RUNNING VEHICLE, in which at this point, I've forgotten what that's like to own. This is my first Jeep after 12 GM vehicles and I'm trying to build a loyalty to the brand, but finding it difficult as my patience is running VERY low. Especially after installing 3 radiators in a month and 2 in under a week. So now it's sitting as I use public transportation, which I hate, until the ENTIRE cooling system is brand new.
If the factory cooling system was touchy from the beginning, has anyone come up with a good aftermarket build that keeps the engine cooler than factory? Trophy truck style? I love building this thing, but I HATE repairing the cooling system every week!
Thanks in advance.

R0CKKR4WL3R 07-03-2013 09:49 PM

Re: ANOTHER overheating WJ
Also...Using Mopar bright orange coolant straight from the dealership.

Frango100 07-04-2013 07:43 AM

Re: ANOTHER overheating WJ
You have any idea what could cause the radiator cracking? Where does it crack to start with, at the plastic tank, or the aluminum core? Does it really crack, or does it form a small hole?
Was the radiator cap changed as well? The radiator cap has a pressure relief valve and if that one doesn´t work (well), it could cause overpressure and a consecutive failure of the weakest part in the system.
The cooling fan issue is strange as well. You see it happen quite often that the fan relay fries, but thats most of the time due to a bad fan which draws too much current. You changed the fan already, so that should be ok. The temperature sensor and the PCM are now left over. But the fan running with the ignition in off, means another fried relay.
I would check all the ground wires, because a bad ground could cause the current flow through other less resisitve paths.

R0CKKR4WL3R 07-04-2013 08:27 AM

Re: ANOTHER overheating WJ
No idea on reason for radiator cracking..if I knew that, I wouldn't come to this site for help. Tired of it cracking though!!!

The first time since I owned it, that it cracked, there was a 10" crack down the driver's side plastic tank. The second time, the crack was small and hidden, I assumed it was near the top, as I was able to limp the vehicle home by stopping, allowing to cool and adding fluid.
This last time, there was a 3" crack near the top of the plastic tank near the radiator cap, surrounded by stress marks or white lines in the plastic.
The cap came with the Jeep and shows no signs of damaging wear, although the release valve in the cap does not seem to exist.
Check all the grounds? In regards to the fan and relay and what else? I just want to make sure I don't miss anything. The relay ground might be a bit of a challenge due to it's location under everything. An access panel has been cut into the heavy plastic, but from there, I have no idea wear that wiring harness goes.
Does the relay use it's mounting bolts to help it ground out through the heat sync into the fender well? Was thinking there might be corrosion in the metal and the mounting location might need to be moved.

R0CKKR4WL3R 07-04-2013 08:49 AM

Re: ANOTHER overheating WJ
Wanted to add...when it overheats, I'm usually in a high traffic area, lots of cars moving slow and lots of red lights. On the highway, it does okay.
The temp gauge, up until yesterday, would go up to 240 and just under 260 before it would pop. At these moments I would pull over and let it cool before it would do so. It would release fluid from the reservoir while sitting for a few minutes. With the fan constantly running, the engine would cool within 20 minutes and I'd be on my way. Yesterday it just barely passed 210 and as soon as I parked it, the radiator popped with a 3" crack and stress marks up high on the driver's side plastic tank.

Frango100 07-04-2013 10:49 AM

Re: ANOTHER overheating WJ
There is a good change that the radiator cap is not releasing the pressure to the overflow tank. That will result in something to break, the weakest point in the system, which probably is the plastic radiator tank. It is always a good idea to change the radiator cap when changing the radiator, its cheap and then at least you know the pressure release valve should be ok. Most of the time the valve opens too early or stays open all the time, preventing pressure buildup and lowering the boiling point of the coolant. In your case it seems to be the opposite.
Did you use the original mopar fan, or some paralel part?
Thinking further about it, you say it would release pressure from the reservoir, you mean the overflow reservoir?
Could be that you have a failing head gasket, which is causing the high pressure and overflow. I would start with a leakdown test to be sure that the head gasket is not the problem.

Carlos Brown 07-04-2013 11:22 AM

Re: ANOTHER overheating WJ

I have never seen this before, sorry! I will say however, that you have several issues here that are not necessarily related. So tackle them as different problems...

Your fan is an issue separate from the overheating issue, although still a problem. If the fan is constantly running (as long as the polarity is not reversed), this is not an overheating issue.

The radiator cap does have to be considered, since a properly operating radiator cap will relieve system pressure long before your radiator would crack. It is only rated at 15 PSI or so, and the radiator will handle quite a bit more pressure than that. So, although cap ay look fine it may still be defective, assuming system pressure is exceeding 15 PSI. If pressure is not the issue then radiators must have some sort of defect or the manner in which they are mounted to the frame is stressing the unit and causing failure.

Now back to system pressure! The system pressure should not get high enough to vent past the cap, particularly if the thermostat is functioning properly and circulating the fluid as it reaching the set temperature. So, does the upper radiator hose get hot once the coolant reaches it's set temperature? This will verify whether or not the thermostat is functioning properly.

Since the system functions fine at speed, your fluid is sufficiently cooling when there is increased flow. So this is normal... However, when there is reduced flow across the radiator you experience reduced cooling.

A few potential issues!
  • Water pump not cycling enough volume at low RPM (defective)
  • Radiator not cooling a high enough volume of coolant as temp rises (clogging)
  • Fan not pulling enough air across radiator to cool coolant (not the issue)

Now regarding the possibility of radiator clogging! Certain coolants will cause a gel to form in the cooling system that can eventually clog the heater core and radiator. Unfortunately, changing these units does not remedy the probem because the gel remains spread throughout the cooling system. I have changed both of these units before and have had the same clogging reoccur within one week. If this probem occurs, traditional system flushing does not clear the system. Flushing will exchange the fluid, but not usually the heavy solids.

How has your heat worked in the Winter? I started removing the heater hoses from the engine and forcing water through them from each direction to clear them. Works much better than the Prestone Flush Kit. This is much more difficult with the radiator however due to it's size and volume.

From Frank:

Could be that you have a failing head gasket, which is causing the high pressure and overflow. I would start with a leakdown test to be sure that the head gasket is not the problem.
Do you notice any constant bubbling in the coolant with the Jeep running? If so, this could be signs of a head gasket problem...

When did the previous owner change the heater core and radiator, and why? How many trouble free miles have you put on the Jeep?

P.S. I can tell when my thermostat opens because at 210* the needle drops 3/16" almost instantly...



R0CKKR4WL3R 07-04-2013 11:34 AM

Re: ANOTHER overheating WJ
Replaced original fan with another Mopar fan. Yes, it is coming from the overflow reservoir, however, hasn't happened in the few days after changing the thermostat. Of course, it's only been a week and before the overflow reservoir could boil out, the radiator cracked instead.
Going to buy a new radiator cap, water pump and temperature control sensor. Thinking about buying a different Mopar fan along with a new relay as well. Just so they're matched, new fan and new relay. In the meantime, the jeep is parked for the week. I can't trust it to cross town if the temp gauge isn't registering the correct engine temp. I'll look into having a leakdown test of the head gasket done as well.
Thanks again for the help!

R0CKKR4WL3R 07-04-2013 11:47 AM

Re: ANOTHER overheating WJ

Previous owner had Jeep and on first hot day popped the radiator. He claims he replaced the rad, water pump and fan. Used Jeep for 2+ years before selling it to me. I racked up 25,000 miles before this issue has occurred with me.
I got it with a cracked heatercore that was seeping. The result was no heat. I replaced the heatercore.
As stated above, I'm letting the Jeep sit for a week until I can acquire the proper parts needed to rebuild the cooling system.
Upper radiator hose IS getting hot and lower is warm, or not as hot as upper hose.
Clogging doesn't seem to be an issue, as I replaced the lower hose yesterday no gel or solids visible. Upper I could see into...same thing. Radiators are new going in, so those definitely are not clogged, and the heatercore I can only assume is the same way. All clear.
Bubbling occurs MOSTLY right after I shut off the engine, I haven't noticed the bubbling otherwise, due to engine noise while running.
Oil does NOT look like a milk shake. Never a puddle on the ground, so it doesn't seem to be leaking any fluids. No white smoke or sweet smell from the exhaust.

Thank you Carlos!

Carlos Brown 07-05-2013 05:49 PM

Re: ANOTHER overheating WJ

The lower radiator hose should be slightly cooler than the upper hose since the hot coolant enters the radiator through the upper hose, cools as it flows down through the radiator, and flows back into the engine through the lower hose. This is good!

R0CKKR4WL3R 07-05-2013 07:37 PM

Re: ANOTHER overheating WJ

FINALLY! Some good news! Thank you! I needed that! So water pump is operating accordingly....correct? No need to swap out?
When it comes to my screen name, you can just spell it out. No need to add the numbers in. It gives me a hard time, sometimes, when I'm logging in. Kicking myself for the choice.
I started the Jeep today with the cap off and let it run. The fluid eventually came up and then dropped down a bit before coming back up again. Unplugging the temp control sensor though, wreaked havoc. The engine kicked up in RPM's a bit and shortly after the radiator boiled over. Temp gauge was at 120 when disconnected, and within moments the radiator just erupted. Plugged in fuse for the fan, killed the motor and restarted a few minutes later and all was back to normal. I'm wondering if the temperature control sensor works intermittently. When it fails, I blow the radiator(s)? Unplugging it made the gauge read absolute zero. which never usually happens when I'm driving. What do you think?
I bought a Stant Radiator Cap with the red release valve today. Valve releases at 18 PSI.

R0CKKR4WL3R 07-06-2013 04:12 PM

Re: ANOTHER overheating WJ
UPDATE: Installed a new Temperature Control Sensor. Let it run for quite a while with no overheating, didn't even budge from the second notch. Let it run a while longer and still no movement in the needle. Checked everything over and no boiling over of the overflow reservoir.
No boiling over, no eruptions, no cracks in the radiator, no leaks, no drips....seems pretty solid. Could this be it? Temperature control sensor wreaked this much havoc?

If that's it, then on to the cooling fan issue and relay. Going to buy a new relay and quite possibly a new fan. I've heard of people saying the relay fails and something gets reversed. "What" is getting reversed? The fan is spinning the opposite direction? What exactly was meant by that? Looking to learn a little bit of how this relay is thinking.

Thanks in advance!

All times are GMT -5. The time now is 12:29 AM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 2012 - JeepGarage.Org
The Jeep Grand Cherokee Owners Community