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Another Overheating TJ.. what next?

18K views 65 replies 27 participants last post by  eruji 
#1 ·
Another Overheating TJ.. what next? **SOLVED**

2001 TJ sport 4.0

Ever since the weather has been getting into the 90 here in so. cali my jeep overheats while idling. This only happens on my way home from work and after ive been on the frwy then stop at a drive in or let it idle for more than 5 minutes. Also, it will sometimes boil in the reservoir as soon as i turn the motor off.

Whats strange is that the temp guage does not slowly raise it goes from 210-220 to redline instantly. If i can get back out on the road and do at least 40mph it will then quickly go back down to 210-220. Seems like the gauge is acting funny. Ive tried turning on the heater and dont notice any reduction in temp. So im not sure if its actually overheating or the gauge or sensor is screwy.

What ive done so far:
New heater core a couple of years ago
new aluminum radiator one year ago
new water pump since april
new thermostat as of this last weekend
new serp belt last weekend
new fan clutch last weekend
EDIT: new rad cap last weekend

no change. still overheats at idle and boils after shut down.

what next?

runs fine otherwise..

is there any way i can monitor engine temp with another device.. diy temp sensor? something? seems strange to me.

where is the temperature gauge getting its data from? ( i think ive read that its not the coolant temp sensor)
 
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#36 ·
I have a 2002 Jeep TJ 4.0 with the same issue, Changed the radiator, therm, hoses, water pump, added a second electric cooling fan 15" pulling 12" pushing and it still overheats only under a load and or with the A/C running. My fan failed and it did get hot on the way home one day. I did the block test and it failed one time however I had a shop repeat the test and it passed three times. No smoke, no water in oil and runs great outside of overheating. Shop thaught it was my Cat. converter.
 
#37 ·
Yup, im still having the problem too. So frustrating. i have not gotten the chem test yet. (how much do those typically cost at a shop?)

I did change the oil this weekend, looks fine, no sludge. I flushed the radiator. filled with distilled and waterwetter only. Changed the thermostat (again). Cleaned the AC evaporator as best as i could. Still overheating.

I just got a bluetooth OBD reader and im using an android app to monitor the temps and such. I will post if I see anything strange.
 
#41 ·
I would verify that the waterpump you put in is designed for the direction it's actually turning. It sounds to me that you may have low water flow. If you look carefully, there are some reverse direction pumps out there, you may have the wrong one. Another thing is that the thermostat on this car should have a jiggler valve in it to eliminate air pockets behind the thermostat. Most parts store ones do not have this. This valve should be located at 12:00 to vent the system right.I always buy thermostats form the dealer only.
 
#42 ·
had a similar issue, top tank was starting to split in the middle. Not the seam. Replaced radiator and have yet to see 220F
 
#43 ·
I would verify that the waterpump you put in is designed for the direction it's actually turning
yes, im leaning towards this now too since it would fit the timeline okay. I had the radiator last summer with no issues, but the water pump was put in this April. Is there a way to test the flow by filling a container a certain volume within a timeframe? Also, if the water pump was flowing in the incorrect direction would it just flow in reverse? or not at all? Where is there a diagram of the path and direction?
 
#49 ·
Will do. I have the original pump so I will compare this weekend. By the way I used my new scanner and software to monitor the coolant temperature on the way home and it went from 205 on the freeway to 245 while idling. And the dash temp gauge hovered around 210 the whole time.
 
#50 ·
Am having exactly the same symptoms in a yj - have had the radiator & thermostat checked out, system flushed etc. My issues started when I had a garage switch my water pumps as the old one failed - am going to check the pump on Sunday to make sure the correct one was put in.
Oh the joys of 'specialist' 4x4 garages....
 
#51 ·
You could save serious money on these changes..just tune it up, most cars this old are 20% down on power due to old O2 sensors, dirty throttle bodies and filters , old plugs an dwires and so on. A good tune up could increase your power 20% while the other stuff you mention is going to be barely noticeable in actual driveability.
 
#52 ·
Filters have all been replaced not very long ago - but o2 sensor, plugs, wires, distribution cap, throttle body etc are all planned for once the suspension is in.
Unfortunately my front left spring is very bent and all the springs (stock I think) have completely sagged, so that's a priority really.
Any power I can get is needed for out here - only stuff around is lots of sand to play in - so no trails, just big dunes to have fun on :)

Back on topic - checked the pump and it seems to be the correct one, so radiator cap next. Had a bit of a play in the sand today with it and as long as the AC is off I hit 210 max on highway driving, and sit at around 200ish idling which is doable.
Unfortunately its around 105 min here during the day at the moment so AC is a necessity (or at least, it is for the gf)
 
#53 ·
One, year later and i think i finally have the solution. Since its Summer again and temps have been increasing my overheating TJ is again an issue. I finally took it to a mechanic who did a chemical test (negative) and a radiator pressure test and noticed that coolant was coming out of the ac condensate tube. I watched him pressurize the system and it was indeed leaking down that tube and onto the floor. I always assumed that it was just water coming out, plus i had replaced the coolant with distilled water and an anti-corrosion and lubricant additive. So the leak looked just like regular water. Im going to bypass the heater core to ensure this is the issue. Hopefully i will be able to finally end this thread with a happy ending.
 
#54 ·
So, that prior post was not the actual solution, yes I did see some leaking from the ac condensate tube, but after bypassing the heater core the overheating was still happening. Last Saturday I broke down and pulled the thermostat out, water pump off and valve cover off, (not necessary, but i wanted to take a look at the top of the head to see if noticed any cracks and to clean all crud building up on the valve cover.) I also took the radiator out and back sprayed the ac fins. While i was looking through the ac fins i realized that my radiator (which i bought new two years ago) i could not see through the fins because they were uniformly mashed on both sides. I cant believe I installed a messed up radiator. The mashed pattern looks very even on both sides, so i just assumed that it was okay, but when i held it up to light i coulsd not see through it. So i called the two dealerships in town to get an OEM one, but neither stocked it and would not get it until maybe tuesday. So i went to my local autozone, they had it in stock and i had him pull it out of the box to check that all the fins were straight and they were.

Here is the radiator that caused me so much grief, the fins on the very edges had less of the mashed pattern than all of the rest of the radiator:


Just for fun, here are my graphs of coolant temp, intake temp, mph,time and such from the Torque android app and my bluetooth OBD reader: (some of the colors changed, but the coolant temp is green in both pics.)
Before:


and After:


Happy to report the jeep is no longer overheating, just have to fix the heater core before the winter. Still cant believe that i put that damn radiator in that condition.
 
#56 ·
I don't believe you installed the radiator in that condition. It looks to me like the tubes swelled from pressure and collapsed the fins to the point where they blocked air flow.

Can you tell by looking if the tubes are straight sided or bulged outwards?
 
#57 ·
Mr. Blaine, thanks for the reply. i took a look at my old radiator and indeed the tubes are swelled in the middle so if you were to slice the radiator in half laterally the tubes would look like this <> <>, so they have swelled so much that the airflow was almost cut off and the fins are folded and blocking it even more. What would cause this? over flow not working properly? cheap radiator. I found my receipt for the radiator and im going to file a claim.
 
#59 ·
The swelling of the tubes is due to either an overpressure situation or a cheap radiator.

Overpressure could come from a faulty radiator cap, but if I were to believe 1/10th of what I see on the 'net, the plastic tanks should have failed first.

Since they didn't, I'm going to go with poor quality radiator.
 
#58 ·
I scanned most of this... have you used compressed air or high pressure water to blow thru the cooler and rad? We play in some soupy stuff down here is south FL and even though there is nothing on the surface does not mean there is nothing in between the fins... I blew out more than 2 pounds of sugar sand with the air then high pressure nozzle out even more... be careful that the pressure is not so extreme that it bends the cooling fins... never mind... Blaine to the rescue

buy good parts... you jeep loves you show it some love back!
 
#60 ·
Thanks guys, feeling a bit better about myself now. I did a google search for similar issues and found a pic of another radiator that has the same folded pattern from the swollen radiator tubes. BTW, no high pressure air or water used to flush things out.
 
#63 ·
Fan clutch is bad.
 
#66 ·
quick update, jeep is still not overheating. new radiator is working. I took it through a slow drive through on a very hot day (100 degrees) and it slowly got to about 222, but quickly down to 210 after moving. No boiling sound when i stop.

peopenn.. how about other components?

entire coolant system: can you pressure test to make sure there are no leaks
heater core: is it clogged up, can you flush or bypass for testing
thermostat: is it working, you can replace or remove for testing
lower hose: does it have the spring in it? is it collapsing under pressure
radiator cap: you can replace or have it tested
water pump: is it failing? usually leaks through weep hole
ac condenser: is it clogged with mud and bugs
assuming your radiator and head is sealed correctly Im not sure what else you can check
 
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