Still overheating

JEEPenn

JEEPenn

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Joined
Sep 22, 2023
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8
Location
Austin Texas
My 89 YJ still overheating and I have invested thousands of dollars trying to address the issue over the last few years.
Replaced the radiator with an all aluminum high performance radiator twice (2 different brands)
Replaced thermostat at least 5 times with everything from 160 degree too 190 degree and even tried leaving it out.
Had head checked for cracks and rebuilt.
Replaced head gasket making extra effort to insure correct orientation of the new gasket.
Replaced fan clutch with correct rotation clutch.
Replaced water pump twice with correct rotation pump.
Tried two different high output electric fans and fan shrouds.
Removed the freeze plugs and pressure washed inside the water jackets on the block.
Replaced all hoses (upper and lower radiator and heater) twice.
Replaced the distributor three times.
Replaced the carburetor twice including completely rebuilding the original 2bbl Carter/Weber 2 times before opting for a Motorcraft 2105.
Flushed entire cooling system with a chemical flush twice and also had a shop use a cooling system flush machine flush the cooling system as well.
Added a high efficiency coolant additive to the manufacture recommended coolant mixture.
Checked that the correct factory OEM radiator fan was being used.
Replaced the serpentine belt three times.
Replaced the harmonic balancer thinking that the outer ring with the timing marks may have slipped slightly causing a slight difference in the accuracy of the timing.
I raised the rear of the hood to allow the engine compartment to vent heat thinking that the heat was not able to escape.
Replaced the temperature sending unit.
Replaced the entire exhaust system from the exhaust manifold to the tailpipe (including the catalytic converter) thinking there was a little restriction.
I did install an a/c (the dealer installed type used in 89) and put an electric fan in front of the condenser (didn’t have that addition in 89).
The overheating issue occurs when the outside temperature is above 60 degrees and ether at idle or driving below 20 mph for around ten minutes (quicker with a/c is on) or when pushing it up above 60 mph especially on inclines (again worse when running the a/c).
If I run the heater it helps bring the temperature down where it stabilizes to around 240 degrees and as low as 220 degrees if it turn off the a/c (when it is 110 degrees outside running the heater becomes unbearable inside the cabin.
If I spray water through the grill the temperature drops to 210 degrees and stays there even when it’s 110 degrees outside and the a/c is on high.
WHAT AM I MISSING???
🙏🏻PLEASE HELP if you know of a fix!
 
Is it puking out coolant? Have you verified the actual temp with a infared temp sensor, their cheap all things considered. How do you know the gauge is reading correctly. Ive had some 12 jeep and several dodge/chrysler vehicles and the electrical systems are piss poor in my experience.
 
It's important to burp the cooling system by raising the front end and start the engine to get the coolant flow moving once the thermostat opens. You can see the air come out with the radiator cap off. The 4.0 and 4.2 are notorious for having air trapped in the back of the cylinder headand disrupting water flow.

I learned that from a dealership who said many shops didn't know about that. That was back in the early 90's.
 
Gilaguy23 said:
Is it puking out coolant? Have you verified the actual temp with a infared temp sensor, their cheap all things considered. How do you know the gauge is reading correctly. Ive had some 12 jeep and several dodge/chrysler vehicles and the electrical systems are piss poor in my experience.
Click to expand...
No not pushing any coolant into the recovery tank.
I have verified the temperature with my IR meter in the past and the temperature is definitely around ten degrees cooler than the gauge inside indicates.
When it reaches around 240 degrees by the gauge the a/c starts to be much less cooler and the oil pressure drops slightly as well as a reduction of engine horsepower and a significant increase in crankcase blow by.
If I continue to push it I’ve noticed that it results in some oil consumption although I have not noticed any exhaust smoke
 
Flyer58 said:
It's important to burp the cooling system by raising the front end and start the engine to get the coolant flow moving once the thermostat opens. You can see the air come out with the radiator cap off. The 4.0 and 4.2 are notorious for having air trapped in the back of the cylinder headand disrupting water flow.

I learned that from a dealership who said many shops didn't know about that. That was back in the early 90's.
Click to expand...
I will give that a try as I have not done that.
Normally I fill the cooling system up with the engine cold then start the engine and let it run adding coolant and the level inside the radiator upper tank until the thermostat cycles several times and the coolant appears to be constantly circulating through the radiator and the coolant level remains within a quarter inch of the cap neck.
I then fill the coolant reserve reservoir to the upper fill line and cap off the radiator and wait to see if the cooling system draws more coolant from the reservoir tank.
 
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Scratching for ideas here. The thermostat in installed correctly. Hows the power like in cam timing off. Positive the water pump is rotating correctly. A pump will pump when running backwards, just not very efficiently. 50/50 coolant mix. fan shroud in place and in good shape?
 
Gilaguy23 said:
Scratching for ideas here. The thermostat in installed correctly. Hows the power like in cam timing off. Positive the water pump is rotating correctly. A pump will pump when running backwards, just not very efficiently. 50/50 coolant mix. fan shroud in place and in good shape?
Click to expand...
Yes to all the above 😉
Take a gander at the huge list of parts and labor that I have done to try and repair the issue.
JEEPenn said:
I will give that a try as I have not done that.
Normally I fill the cooling system up with the engine cold then start the engine and let it run adding coolant and the level inside the radiator upper tank until the thermostat cycles several times and the coolant appears to be constantly circulating through the radiator and the coolant level remains within a quarter inch of the cap neck.
I then fill the coolant reserve reservoir to the upper fill line and cap off the radiator and wait to see if the cooling system draws more coolant from the reservoir tank.
Click to expand...
Flyer58 I have had a chance to try and “burp” the cooling system per your suggestion.
I drove the front up on ramps and deflated the rear tires that placed the vehicle in a 16 degree nose up position.
I opened the radiator cap and started the engine and let it run until the thermostat quit cycling and I had a constant flow through the radiator upper tank then I resealed the radiator cap.
During the entire process no air bubbles were detected in the radiator tank and it did overflow about 1/4 cup of coolant.
I used my no contact temperature tester and at the sensor/sending unit the temperature read 210 degrees and the gauge read 220 degrees.
At the thermostat housing the temperature reading was 180-185 degrees. I currently have a 180 degree thermostat in it.
The outside temperature was around 100 degrees and the humidity was high.
All readings were at idle without the A/C running.
When I turned on the A/C the temperature immediately started climbing and within 5 minutes had risen to 260 degrees.
I checked the electric condenser fan that I had installed about 5 years ago and noticed that it was turning but like it was on low speed.
It was rated at 800 cfm and I recall that it was blowing MUCH harder when I installed it.
I have ordered a new condenser fan that will be delivered tomorrow and it is rated at 1670 cfm.
Maybe that was the the main issue
 
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JEEPenn said:
Yes to all the above 😉
Take a gander at the huge list of parts and labor that I have done to try and repair the issue.

Flyer58 I have had a chance to try and “burp” the cooling system per your suggestion.
I drove the front up on ramps and deflated the rear tires that placed the vehicle in a 16 degree nose up position.
I opened the radiator cap and started the engine and let it run until the thermostat quit cycling and I had a constant flow through the radiator upper tank then I resealed the radiator cap.
During the entire process no air bubbles were detected in the radiator tank and it did overflow about 1/4 cup of coolant.
I used my no contact temperature tester and at the sensor/sending unit the temperature read 210 degrees and the gauge read 220 degrees.
At the thermostat housing the temperature reading was 180-185 degrees. I currently have a 180 degree thermostat in it.
The outside temperature was around 100 degrees and the humidity was high.
All readings were at idle without the A/C running.
When I turned on the A/C the temperature immediately started climbing and within 5 minutes had risen to 260 degrees.
I checked the electric condenser fan that I had installed about 5 years ago and noticed that it was turning but like it was on low speed.
It was rated at 800 cfm and I recall that it was blowing MUCH harder when I installed it.
I have ordered a new condenser fan that will be delivered tomorrow and it is rated at 1670 cfm.
Maybe that was the the main issue
Click to expand...
OMG!!! Just figured out your problem, it’s global warming,,,,,I mean climate change, hashtag tree hugging emoji BS. Crazy uncle Joe has a whole bunch of battery powered trash for us to buy and no more cooling problems. And probably no more traveling problems either.
 
Just by chance, because I've seen it before, is the electric fan spinning the proper direction or is it fighting against the engine fan for airflow direction? Like I said I've seen it when the fan supplier had reversed the wire color and the airflow was butting heads between the two fans. I find it interesting that the AC on would cause this.
 
Flyer58 said:
Just by chance, because I've seen it before, is the electric fan spinning the proper direction or is it fighting against the engine fan for airflow direction? Like I said I've seen it when the fan supplier had reversed the wire color and the airflow was butting heads between the two fans. I find it interesting that the AC on would cause this.
Click to expand...
Yes when I installed it I took special care to make sure that it was blowing air through the condenser and not the grill.
When the AC is on the condenser gets extremely hot especially when the temperature outside is hot and the humidity is very high.
Like I mentioned I recall the condenser fan originally blew pretty hard and you could hear it pushing the air through the condenser when it was on.
I now notice that there is literally very little fan sound.
My thoughts are that if the condenser fan is just lightly blowing air through the extremely hot condenser onto the radiator that it would GREATLY reduce the ability for the radiator to cool down the engine coolant.
This actually makes sense because if I run the heater (basically a miniature radiator) it brings the engine temperature down a good 20 degrees.
There is no super heated air blowing on the heater core and makes it more efficient even though it is much smaller than the radiator.
I will know if that theory is correct in a couple days!
 
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JEEPenn said:
Yes to all the above 😉
Take a gander at the huge list of parts and labor that I have done to try and repair the issue.

Flyer58 I have had a chance to try and “burp” the cooling system per your suggestion.
I drove the front up on ramps and deflated the rear tires that placed the vehicle in a 16 degree nose up position.
I opened the radiator cap and started the engine and let it run until the thermostat quit cycling and I had a constant flow through the radiator upper tank then I resealed the radiator cap.
During the entire process no air bubbles were detected in the radiator tank and it did overflow about 1/4 cup of coolant.
I used my no contact temperature tester and at the sensor/sending unit the temperature read 210 degrees and the gauge read 220 degrees.
At the thermostat housing the temperature reading was 180-185 degrees. I currently have a 180 degree thermostat in it.
The outside temperature was around 100 degrees and the humidity was high.
All readings were at idle without the A/C running.
When I turned on the A/C the temperature immediately started climbing and within 5 minutes had risen to 260 degrees.
I checked the electric condenser fan that I had installed about 5 years ago and noticed that it was turning but like it was on low speed.
It was rated at 800 cfm and I recall that it was blowing MUCH harder when I installed it.
I have ordered a new condenser fan that will be delivered tomorrow and it is rated at 1670 cfm.
Maybe that was the the main issue
Click to expand...
You really should go back to the mechanical fan. Aftermarket electric fans are typically garbage and don’t flow near the proper amount of air. I know you still had issues when you had the clutch fan before, but maybe you had other issues in addition that have since been fixed. I’ve been on the forums a long time and an unbelievable amount of cooling problems are directly related to aftermarket e-fans.
 
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machoheadgames said:
You really should go back to the mechanical fan. Aftermarket electric fans are typically garbage and don’t flow near the proper amount of air. I know you still had issues when you had the clutch fan before, but maybe you had other issues in addition that have since been fixed. I’ve been on the forums a long time and an unbelievable amount of cooling problems are directly related to aftermarket e-fans.
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machoheadgames I AM using the original mechanical fan system.
As I had mentioned on a couple posts that I had replaced the fan clutch (the part that links the five blade steel fan to the water pump hub) a couple of times thinking that the fan clutch had failed and the replacement was defective.
Although I have ALSO Tried the electric fan route going with several different fan configurations before finally abandoning the electric radiator fan concept completely.
I believe that your misunderstanding came from the fact that I am using an electric fan to assist in cooling the condenser in my air conditioning system. The electric fan is mounted to the front side of the condenser between the grill and condenser and ONLY comes on when the air conditioner is turned on.
 
JEEPenn said:
machoheadgames I AM using the original mechanical fan system.
As I had mentioned on a couple posts that I had replaced the fan clutch (the part that links the five blade steel fan to the water pump hub) a couple of times thinking that the fan clutch had failed and the replacement was defective.
Although I have ALSO Tried the electric fan route going with several different fan configurations before finally abandoning the electric radiator fan concept completely.
I believe that your misunderstanding came from the fact that I am using an electric fan to assist in cooling the condenser in my air conditioning system. The electric fan is mounted to the front side of the condenser between the grill and condenser and ONLY comes on when the air conditioner is turned on.
Click to expand...
I see now. I had seen clutch fan mentioned early on, but then only electric mentioned recently which led me to believe the clutch setup had been ditched.

That said, you shouldn't need the aux electric fan to not overheat either. I've heard a lot of bad about the all aluminum radiators, have always seen much better luck with the Mopar radiators, not that those are available anymore though.
 
Just a friendly reminder. The thermostat controls the minimum operating temperature while the radiator is what controls the maximum temps. If I recall correctly the fuel injected engines require the 190 degree stat.

Did you get a new radiator cap with the new radiator? Is it for the correct pressure? Is the coolant level in the reservoir staying within the hot/cold limits after driving several times?
 
machoheadgames said:
I see now. I had seen clutch fan mentioned early on, but then only electric mentioned recently which led me to believe the clutch setup had been ditched.

That said, you shouldn't need the aux electric fan to not overheat either. I've heard a lot of bad about the all aluminum radiators, have always seen much better luck with the Mopar radiators, not that those are available anymore though.
Click to expand...
machoheadgames I really didn’t have an overheating issue when I first installed the A/C but I did notice a difference in the cold air output from when I was driving down the road and when I was stopped in traffic or sitting idle. I hooked up my A/C manifold set and the high side pressure would climb to 250-350 lbs when sitting idle and the pressure would drop back to 200 lbs when I place a 12” high velocity shop fan directly in front of the grill blowing on the condenser.
I installed an 80 amp 12” 800 cfm fan between the grill and the condenser and that fixed the high pressure issue and the air conditioner blew cold whether I was driving or stopped and had no overheating issues then.
That was about 5 years ago
 
update my 95yj, this PCM has 2 fast idle pins , pin 27 and 28
the FSM explains how it works.
in SHORT:
driver flips dash A.C knob to on.
pcm sees that act on 28 , "select sense pin"
then RPM goes to PCM mapped, RPM for AC on, my guess 1000, (still wiring mine up now) << hard to reach wires on mine
then when programmed RPM is reached (ckp sensor RPM) the PCM then engages the clutch of the compressor
and regulates RPM agressively. IAC not gummed up that is.
and it also reads back on pin 27 that clutch did get power.12vdc. (13 to15v actual)

the clutch fan stock is super powerful. with the duct'ed shroud.
agreed!
fans on condenser, may be needed. the FSM states, these run, overheated or A/C is active.
I guess it is solved now?
Mine never overheats, even 110f outside but I am doing the PCM fast idle mode, to make mine just like factory A.C, when AC is on Fast idle is enabled. to PCM
not sure what PCM you run here, 87?

I will post the secret RPM my PCM does, not told an the 3 service, manuals I have SM, EFI and diagnostic, ,it does say it has Idle UP mode for AC but never discloses what.
i have a RPM digital optical hand meter that is dead accurate for RPM. (no DRB here to see RPM)

the IAC is a servo and all cars made run it in 3 modes{or more} (to avoid IAC RPM hunting) the rule is GAIN
at idle in neutral gain is low, so RPM regulation is slow and gentle, but Reliable.
then in DRIVE ( a/t box) it goes aggressive and high gain
the IAC+PCM servo goes to to aggressive mode.
if engine EFI is running great , in closed loop all is well but if not and running lean , the idle speeds fail.

this is why modern cars use TBW throttle by wire. (TB motor drive)
1000RPM is very common RPM on small engines,A/C on, I can name many.
when at that RPM the fan is way more effective say at red stop sign , 110F out and works perfectly

I am not prevy of all your driveline mods so my anwers can be dead wrong. Jeeps tend to be not stock this old, endless examples.
 
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