TJ Cooling System Dilemma

[JayW-2006LJ]

All water pumps are not created equal . My neighbor has an automotive shop and a customer brought in a truck that had the water pump replaced six months prior at another shop . The truck kept running hot . That shop replaced everything in the cooling system and could not fix the overheating problem . My neighbor started diagnosing it by removing the "new" water pump and found that the impeller was spinning on the shaft . Installed a good quality water pump and overheating issue was fixed .

There has been plenty of discussions about aftermarket radiators not cooling as well as OEM .
I just ordered a Koyorad A2102 based on information from Irun's research . Also a Robert Shaw 330-195 thermostat based on macLeanflood recommendation .

It will be a couple of weeks before I can work on it , I have to let the burns heal . This happened Tuesday afternoon a day of wheeling . You can read the thread and find the link discussing the radiator options .

View attachment 621612

ouch! Mechanic doesn't think the water pump is an issue.... I'm letting him replace the rad so I can get back on the road, but I'm ordering a Mopar pump and will put that in one of these weekends. Thanks for the info!

 

[xXDavidCXx]

2025 Update to this 2023 post.....
Recap: 2006 TJ Unlimited (LJ), 4.0 engine, 6sp manual 160,000 mi, owned since new.
Feb 2023: Water pump went out, had mechanic put in a new one, plus radiator cap and thermostat
When they completed it and did a test drive, the heater core blew out, so they installed a bypass (u-turn, not plugged lines)
A few days later, my radiator blew while driving in traffic.
Mechanic was swamped, so I put one in (NAPA) myself.
July 2023: Intermittent overheating at idle. I bled the system, and put in a new fan clutch, just to eliminate that variable
Sept 2023: Still intermittent overheating, installed new thermostat, bled the system of air.
Jan 2024: Still overheating at long idle, replaced thermostatu with Mopar, suspected previous one was faulty
Ran cylinder pressure test, all OK
June 2024: Idling in parking lot for 30+ min with A/C on max (Florida heat); pressure built up and blew hose AND radiator. New radiator, cap and hose. Also head diagnostics to make sure head gasket was not blown - test negative

June 2025 NEW UPDATE: Idling in parking lot for 30+ min with A/C.... Noticed that temp guage was just above center, so I shut it off (probably should have driven to cool things down). 5 min later, radiator BLEW (hole in body of radiator, 3" split in top, next to cap. Mechanic did head test again - still negative. They are putting in new radiator (#3) again.....

Two things:
1. I have an aluminum decorative flag in the grill, in front of the radiator (aluminum, with small holes punched to let air flow through). I installed in 2020, 3 years before the overheating issues. Mechanic is going to remove with this new radiator, just to eliminate it as a variable - Could this be a contributing cause?
2. Should I think about replacing the water pump with a MOPAR model? I can't imagine the water pump is causing these issues, but it all started when this pump was installed in 2023.... There isn't much left in the cooling system.

P.S. heater core bypass is still installed - waiting for me to summon the energy to tear apart the entire dash.

Thanks for any input anyone has!!
JW

1. Temps just above the center, does this mean just right of 210? If so, that's not overheating.

2. When was the last time you did a thermo cure or prestone cooling system cleaner?

3. Sounds like you just have a quality radiator problem.

 

[JayW-2006LJ]

1. Temps just above the center, does this mean just right of 210? If so, that's not overheating.

2. When was the last time you did a thermo cure or prestone cooling system cleaner?

3. Sounds like you just have a quality radiator problem.

1. Temps just above the center, does this mean just right of 210? If so, that's not overheating.

Correct, that is where it was hovering (this time), just before the radiator blew. I didn't want it to "red-line", so I shut it off (I know, I should have driven around instead). Then, 5 min later, it blew. The mechanic found, in addition to the 3" crack next to the filler neck, another pinhole it was leaking from. I am wondering if it had a slow coolant leak, then the gas overheated and blew it out. If the coolant was low enough, it is possible that the temp sensor wasn't registering the hot gases. With the previous episodes, the gauge did get into the red zone.

2. When was the last time you did a thermo cure or prestone cooling system cleaner?

It has been awhile - not sure if they did it with the previous services, but this new replacement work included a flush.

3. Sounds like you just have a quality radiator problem.

I agree. There were some other things (not adequate bleeding of the air in the system) before, but also, the radiators were crap.

1. Temps just above the center, does this mean just right of 210? If so, that's not overheating.

2. When was the last time you did a thermo cure or prestone cooling system cleaner?

3. Sounds like you just have a quality radiator problem.

Thanks for the response!

 

[xXDavidCXx]

Looking forward to better results with the next radiator.

 

[JayW-2006LJ]

Looking forward to better results with the next radiator.

so am i!.... Curious to see if anyone thinks it would be good to just replace the 3-year old after market water pump with a Mopar one, just to eliminate that variable....?

 

[xXDavidCXx]

If the cooling system can’t contain the pressure the temp increases and either blows out at the weak point or maybe boils over if the issue is the cap.

At this point, I don’t think the issue is the pump.

 

[JayW-2006LJ]

If the cooling system can’t contain the pressure the temp increases and either blows out at the weak point or maybe boils over if the issue is the cap.

At this point, I don’t think the issue is the pump.