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  #1  
Old August 23rd, 2015, 19:02
kc_eiland kc_eiland is offline
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Still Overheating. EVERYTHING changed.

I've searched here, and there, and over the web and everyone says to do the same things to remedy the overheating issues.... well I've done all of them and its still overheating. As the title states, my 2000 4.0 is still overheating after I've changed every part in the cooling system. It only overheats at idle (stop lights, drive thru lines, etc...). It WILL overheat with AC turned off but takes a while, but it overheats within 5-10 mins with AC on at idle. While driving/moving, it maintains 210* (with or without AC on).

It started overheating at the beginning of the summer. Since then, I've replaced/done:

Radiator
Upper Radiator Hose
Lower Radiator Hose
Thermostat (195*)
Thermostat Housing
Coolant Temp Sensor
Water Pump
Hood Vents
Fan Clutch (First replaced with XJ fan clutch, then tried ZJ fan clutch which is currently installed now)
Radiator Cap
Flushed coolant (twice)
Checked for head/gasket leaks by certified mechanic (no oil in coolant, no coolant in my oil, no exhaust in my coolant, no coolant leaking into my exhaust, bore scoped every cylinder for traces of coolant, checked compression, leak checked coolant system, etc...)
Checked electric fan, (comes on around 218*ish) -- best I can tell from the temp gauge.
Checked for cracks/leaks in the overflow bottle.... none found.

All checks are good. Jeep runs great. I'm at a loss. The ONLY thing I haven't changed is heater core and heater core hoses.

Someone please help. I'm willing to try anything (including changing the stupid heater core if someone mentions it). I'm really debating getting rid of my Jeep if I cant get this problem solved.
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  #2  
Old August 23rd, 2015, 20:02
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stockerwithalocker stockerwithalocker is offline
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Re: Still Overheating. EVERYTHING changed.

What are you considering overheating? Meaning it boils over or the temp gauge rises above 220? From what you are describing it sounds like somehow your e-fan (I read you checked it and it works) is not functioning correctly, especially if it overheats so quickly with the AC on.
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  #3  
Old August 23rd, 2015, 20:05
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Re: Still Overheating. EVERYTHING changed.

what brand/type radiator?

bypass the heater core to test.
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  #4  
Old August 23rd, 2015, 21:50
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Re: Still Overheating. EVERYTHING changed.

Heater core shouldn't effect your cooling negatively if it is plugged. Just means no heat. Only way it can cause an overheat is if it is leaking and you are loosing coolant but you tend to notice it. Maybe a cracked cylinder head? 00 and 01s are prone to cracking between cylinder 3/4 but usually you just get coolant in the oil and it eventually wears out your lower end. Only other thing I can think of is to do a compression test and see if you have a bad head gasket.
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  #5  
Old August 23rd, 2015, 22:26
md21722 md21722 is offline
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Re: Still Overheating. EVERYTHING changed.

Otherwise unexplainable temperatures are frequently a blown head gasket or cracked head or both. Sometimes the head/head gasket will test fine cold but will open up when hot. I would check to make sure the condenser isn't clogged with dust and dirt. You probably did when you replaced the radiator. What was the old and new radiator make/model?
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  #6  
Old August 24th, 2015, 10:51
kc_eiland kc_eiland is offline
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Re: Still Overheating. EVERYTHING changed.

Thank you all for the replies. As for "overheating" the temp will slowly creep to the 230* range then peg to the redline with the "Check Gauges" light on. As soon as I start driving/moving, it will drop back down to the 230* range and slowly creep back to 210*... until I hit another red light and it starts to creep again. It pegging to the red has only happened twice and stayed there for 5-10 seconds before I either started rolling or turned the Jeep off.

Additionally, If the Jeep was running around 220*ish, it will sometimes boil over from the radiator cap after parked.

The radiator I replaced was the original radiator. The new radiator I installed was from NAPA (the more expensive aluminum one).

As for the heater core, the heat does work. The system was tested for leaks/pressure loss while hot (210-220*). Coolant levels are high, except when it boils over but I immediately refill what was lost after it cools down.

As for the cylinder head, I had the mechanic check specifically for the cracks, leaks, etc... He was well aware of the 0331 heads and the problems those carry. He performed a compression test as well with no negative findings. He also pulled the plugs and bore scoped (ran camera) thru every cylinder to look for traces of coolant/wear. All looked great. All of this was done with the Jeep at 210*ish.

As for the condenser, I will double check that. The AC is ice cold which leads me to believe that the condenser is clear, but it definitely wont hurt to check again.

Thanks again for all the input. Please keep it coming and hopefully we can find a solution. FYI, I've ordered the triple fan set up from Dirtbound. I will give that a shot whenever it decides to arrive and post the results. I definitely don't want to "mask" a problem(s) I may have. I'd like to find the root cause (if there is one other than airflow) and get it fixed.
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  #7  
Old August 24th, 2015, 11:34
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Re: Still Overheating. EVERYTHING changed.

Key is that it works properly at highway speed then explodes at idle. That really points to the fan or the water pump (low RPM at idle = low CFM), but could also be some kind of restriction in the airflow (or fluid flow). One thing to check, when you come to a red light try holding the RPMs up and see if the behavior changes any.
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  #8  
Old August 24th, 2015, 11:58
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Re: Still Overheating. EVERYTHING changed.

There are several things that are left that can cause overheating. The first would be running too lean. Get a vacuum gauge and follow the instructions on measuring and evaluating the meter's actions. You could have a vacuum leak. Most common is under the battery. Do the brakes work OK? A leaking vacuum booster can cause a ton of extra air.

The next would be to test the MAP sensor.

How is the power? If it falls off at higher speeds, it could be a clogged CAT.
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  #9  
Old August 24th, 2015, 12:01
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Re: Still Overheating. EVERYTHING changed.

make sure the belt isn't misrouted and turning the coolant pump backwards.
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  #10  
Old August 24th, 2015, 12:43
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Re: Still Overheating. EVERYTHING changed.

I have hard but never experienced this myself that if you replace the lower radiator hose without reading the spring insert that goes into that the original would have had that it can collapse causing flow restriction.
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  #11  
Old August 24th, 2015, 13:01
cliff h cliff h is offline
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Re: Still Overheating. EVERYTHING changed.

I did this mod. and it seemed to help some:

http://www.go.jeep-xj.info/HowtoRadiatorRestrictor.htm

I also had an issue where my gauge was pegged to full hot on occasion. I had air in my cooling system that I did not discover untill I replaced my coolant temp. sensor located in the thermostat housing. When I removed the sensor, there was no coolant touching the sensor when I removed it. Since I already had the sensor, I replaced it, and filled the cooling system thru the sensor hole before I replaced it.
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  #12  
Old August 24th, 2015, 13:18
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Re: Still Overheating. EVERYTHING changed.

Kill your order with Dirtbound. Your stock fans move WAY more air than those. You are wasting your money with that.

Let's go back to the beginning.

When did it start overheating? Was there any work done or parts replaced just prior to your overheating issues?
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  #13  
Old August 24th, 2015, 13:21
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Re: Still Overheating. EVERYTHING changed.

Quote:
Originally Posted by devildog0 View Post
make sure the belt isn't misrouted and turning the coolant pump backwards.
Or turning the fan backwards. I have also seen where a new water pump had an impeller for clockwise rotation instead of counter clockwise.
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  #14  
Old August 24th, 2015, 13:34
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Digger87xj Digger87xj is offline
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Re: Still Overheating. EVERYTHING changed.

The electric fan should be on or cycling frequently with the a/c on.
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  #15  
Old August 24th, 2015, 14:56
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Re: Still Overheating. EVERYTHING changed.

Quote:
Originally Posted by cliff h View Post
I did this mod. and it seemed to help some:

http://www.go.jeep-xj.info/HowtoRadiatorRestrictor.htm

I also had an issue where my gauge was pegged to full hot on occasion. I had air in my cooling system that I did not discover untill I replaced my coolant temp. sensor located in the thermostat housing. When I removed the sensor, there was no coolant touching the sensor when I removed it. Since I already had the sensor, I replaced it, and filled the cooling system thru the sensor hole before I replaced it.
Restrictor would be fine in a cold environment, but not in Vegas. A good quality high-flow thermostat is what he needs -

http://www.summitracing.com/parts/em...merican-motors
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