TJ Cooling System Dilemma

[JayW-2006LJ]

OK, new member here, first post. Forgive if this has been covered...
I've got a 2006 Unlimited, bought it on the showroom in 2005. 150,000 miles Manual transmission (6-speed)
2 weeks ago I ran a 200-mile day trip, which is way more than I ever travel in the Wrangler under normal conditions. Ran perfectly.
Next morning, I started it and heard the tell-tale clanging from the engine and had coolant leaking out the bottom of the water pump. OK, so the water pump crapped. Never been replaced.

Read up on the how-tos and didn't have time, so I took it to my mechanic to have it replaced. Based on research, I also requested a new thermostat while they were at it. Both were original.

They did the work, test drove it, and coolant was pouring out from the A/C condensate line - the heater core had blown out. Was replaced 4 years ago. Since I'm in Florida and heat is not critical, they just bypassed the heater core to get the Jeep back to me.

Two days later, in stop/go city traffic, coolant started spewing from the grill, up, onto the windshield. 3"+ long crack in the radiator, next to the cap. (Yes, the cap had been replaced with the water pump and the thermostat - 18# cap from NAPA).

Mechanic was too busy to look at it, so I took it back and replaced the radiator myself with an after-market model from NAPA. I also replaced the radiator cap (again), just to be safe.
Fearing head gasket issues, I also got the gauge to do a compression test on the cylinders to see if there was any obvious weak spots. I ran the test 2x on each cylinder and got average readings of 151 - 191 on all six cylinders, so I felt better about the head gasket.

Everything back together with no issues, ran with cap off to check and bleed out any air - everything checked out great, no leaks, running at 212 degrees+/-, no overheating.

Today was the first longer trip around town and it ran great with no issues - until I parked for a few minutes with the A/C on max. The temp gauge shot up to the red zone and the warning "Check Gauges" message came on. Turned the A/C off and got back on the road and it cooled right back down. When I got home I checked to make sure the fan was running - it was. I let it idle for 20 min with the A/C on high at home and no problems.....

Original question was going to be about the possible pressure issue (change the water pump and thermo, and suddenly the heater core and radiator both blow out).
Now I'm also wondering if the possibly sporadic overheating might be a separate issue.

Thoughts? I'll probably take it to the mechanic next week and have them pressure test the system and maybe do the die test for exhaust fumes in the coolant.
Thanks!
JW

 

[Zef]

My guess is your radiator was no longer doing a good job. But the heater core was "helping it out". Then your heater core blew. You bypassed it and now your radiator showed its weakness and blew too.

As for your current issue - I suspect you have air in the cooling system. Unscrew your temperature sensor and slowly add coolant to the radiator until coolant comes out the sensor hole. Front of vehicle a little higher than rear... it's either that or the new radiator is bad (if it is I recommend getting a Denso - they're a tier 1 supplier and a perfect fit).

 

[Jerry Bransford]

Absolutely could be air in the system as Zef suggested. But that can also be caused by the thermostat sticking shut, I wonder what brand of thermostat the mechanic installed. If it was a store brand or a cheap brand that is a possibility. My usual go-to brand Stant is no more, I'd run to the local Jeep, Dodge, or Chrysler dealer and get a replacement Mopar thermostat, make sure it's a 195 degree version though that's what is used in most of their engines.

 

[JayW-2006LJ]

Absolutely could be air in the system as Zef suggested. But that can also be caused by the thermostat sticking shut, I wonder what brand of thermostat the mechanic installed. If it was a store brand or a cheap brand that is a possibility. My usual go-to brand Stant is no more, I'd run to the local Jeep, Dodge, or Chrysler dealer and get a replacement Mopar thermostat, make sure it's a 195 degree version though that's what is used in most of their engines.

Thanks to both you and Zef, I'll check the air and look to see what brand thermo they put in. They always get their parts from NAPA, so I suspect it was a cheap one. I've also thought about the fan clutch. Seems to be working, when the engine is at operating temp and I shut it off, it is pretty stiff, definitely not 'free wheeling' - I can only 'spin' it about 20 degrees. Another part that wouldn't hurt to just replace, in case it is an intermittent issue. The clutch is also original, 2006 equipment. I'll report back my findings. Thanks again.

 

[JayW-2006LJ]

My guess is your radiator was no longer doing a good job. But the heater core was "helping it out". Then your heater core blew. You bypassed it and now your radiator showed its weakness and blew too.

As for your current issue - I suspect you have air in the cooling system. Unscrew your temperature sensor and slowly add coolant to the radiator until coolant comes out the sensor hole. Front of vehicle a little higher than rear... it's either that or the new radiator is bad (if it is I recommend getting a Denso - they're a tier 1 supplier and a perfect fit).

Thanks very much - see my response to Jerry as well. I'll try out the suggestions and get back.

 

[tanguay]

WOW - you had a very similar Saturday as I did. 2005 TJ (X 4.0L Manual) stop and go traffic on I4 over heated and now looking to fix it all at once.

I am assuming the fan clutch is done as the fan spins more than I would like.

Trouble is the recommended MOPAR radiator is discontinued. Are there any good replacements out there? @Zef you mentioned Denso - any feedback? @Jerry Bransford - any time you comment i listen. Your words are gold.

Thank you for your help. Been a long time stalker on these forums!!

 

[KennethS]

They always get their parts from NAPA, so I suspect it was a cheap one.

NAPA typically carries several lines of parts, with the higher quality / higher priced parts being better ones, but you have to specify you want the better ones.

 

[JayW-2006LJ]

My guess is your radiator was no longer doing a good job. But the heater core was "helping it out". Then your heater core blew. You bypassed it and now your radiator showed its weakness and blew too.

As for your current issue - I suspect you have air in the cooling system. Unscrew your temperature sensor and slowly add coolant to the radiator until coolant comes out the sensor hole. Front of vehicle a little higher than rear... it's either that or the new radiator is bad (if it is I recommend getting a Denso - they're a tier 1 supplier and a perfect fit).

I've been too busy to get the Jeep to the mechanic for the pressure test, but I did check the air in the system as recommended. I've got a slight slope on the driveway, so that worked for the front end being higher. The temp sensor tip was great - surprisingly, it took over a quart of coolant before it started coming out of the hole. Obviously, there was some air in there! I've run it over 150 miles - all in city, stop/go traffic with the A/C running and the temp at 85 degreees outside. The temp never got more than a needle width above 210 when idling and a bit below 210 while driving.

Thanks very much for the input!

 

[JayW-2006LJ]

WOW - you had a very similar Saturday as I did. 2005 TJ (X 4.0L Manual) stop and go traffic on I4 over heated and now looking to fix it all at once.

I am assuming the fan clutch is done as the fan spins more than I would like.

Trouble is the recommended MOPAR radiator is discontinued. Are there any good replacements out there? @Zef you mentioned Denso - any feedback? @Jerry Bransford - any time you comment i listen. Your words are gold.

Thank you for your help. Been a long time stalker on these forums!!

Once I bled the air out the right way, mine has been running great. For what it is worth, my replacement radiator at NAPA is their brand, part NR 1015B, for $175. They had a much more expensive model, but it didn't list a warranty. This one has a lifetime warranty, so I figured it was worth the gamble.

Best of luck with the 2005!

 

[Jerry Bransford]

Once I bled the air out the right way, mine has been running great. For what it is worth, my replacement radiator at NAPA is their brand, part NR 1015B, for $175. They had a much more expensive model, but it didn't list a warranty. This one has a lifetime warranty, so I figured it was worth the gamble.

Best of luck with the 2005!

Good results, good work. But where a radiator is concerned I'd rather pay more and get a better quality product with a 12 month warranty vs. a lifetime warranty that even the cheapest/shoddiest radiators all seem to come with now. Just like I'd rather have a Mopar radiator with a 12 month warranty than any store brand or cheap online brand radiator with a lifetime warranty.

 

[JayW-2006LJ]

 

[tanguay]

The Denso got delivered yesterday, so the install begins tomorrow.

Got all new hoses too since I've got everything out of the way to replacement them and there is no telling how old they are.

 

[Jerry Bransford]

Install a new 195 degree non-failsafe thermostat too.

If it has a vent hole in it make it gets positioned at the top so it can pass trapped air out. If it doesn't have one, drill one like below.

 

[tanguay]

Bought the Stant Superstat 195 degree, like you suggested above @Jerry Bransford

 

[JayW-2006LJ]

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

 

[ItchyDong]

Was it the NAPA radiator that gave it up? Seems to me like it’s been fine for 2 years and someone warned you about cheap radiators…

 

[JayW-2006LJ]

Was it the NAPA radiator that gave it up? Seems to me like it’s been fine for 2 years and someone warned you about cheap radiators…

First radiator that went was the original (in 2023). 2nd was a NAPA one (in 2024). Not sure where the current one that just blew came from (via my mechanic). Unfortunately, the OEM's for this model have been discontinued for some time. I will need to do some research on what ones are out there as quality, 3rd party units. Thanks!

 

[OldBuzzard]

@Irun just did a review of a bunch of radiators in his "It Just Happened" thread starting here.

 

[Harold&Cat]

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 .

 

[JayW-2006LJ]

@Irun just did a review of a bunch of radiators in his "It Just Happened" thread starting here.

Thanks, I'll check that out!