2004 TJ 4.0 overheating at idle after cooling system overhaul

[Jerry Bransford]

Its an $800+ locally made racing Radiator. The material and craftsmanship is better than any aftermarket radiator. I know this means nearly nothing if it is a poor design for the application though. I do run 200-205F on the freeway though. Wouldn’t this mean my radiator is working correctly?

You've got 65-70 mph air moving through the radiator at cruising speeds, it's easy for a radiator to keep things cool there. Superb materials and craftsmanship don't necessarily it's a good design or a design that is suitable for how a Jeep is driven. It's hard to believe for some but the OE Mopar radiator is really tough for an aftermarket radiator to beat, let alone match, its cooling ability. And make no mistake, more rows in a radiator is no indication it will cool better. Mopar went from a 2 row to a 1 row radiator a year or two after the TJ was introduced and with that redesign better overall cooling was the result.

 

[JSpike]

Let's go back to basics again !!! At a idle in drive way put a fan in front of radiator and see if temp drops,not a huge fan. If temp drops then you have a air flow problem, the air is not being pulled thru radiator. My guess is radiator, 2 row is harder to pull air thru clutch and fan designed for 1 row. You could add a electric fan in front if you wanted to keep radiator.

 

[eastbloc]

Your system has a problem then, Florida doesn't get that hot. We wheel the deserts of SoCal with the OE Mopar radiators without any problems at all. Aftermarket radiator? Bad fan clutch?

Everything is fresh and just the way it should be.
I have no problems, and i dont see how getting to 230-240 in a span of 10 - 30 min while idling in 100+ humid oven weather is a problem.
If that was the case during slow movement/crawl/traffic, that be a different story.


... Matter of fact, i did re-read OP post
"only happens at idle and slow speeds where my temp gauge will get to 220-230 and the engine starts running rough" <—- yes that sounds like a problem

 

[Flivver250]

I have a relatively stock cooling system and my Jeep operates in temperatures that routinely exceed 115°. Sometimes considerably. I can idle all day. As others have stated, radiator and fan clutch are the best starting point. Also, consider the coolant you used. I had a buddy buy a bargain brand that may well have been colored water. We flushed it out and put in a quality coolant and problem solved. I suspect his bogus coolant was a knock off. Something to consider, when these rigs were originally equipped with all stock parts, the rigs did not overheat.

 

[Jacob Boehmer]

You've got 65-70 mph air moving through the radiator at cruising speeds, it's easy for a radiator to keep things cool there. Superb materials and craftsmanship don't necessarily it's a good design or a design that is suitable for how a Jeep is driven. It's hard to believe for some but the OE Mopar radiator is really tough for an aftermarket radiator to beat, let alone match, its cooling ability. And make no mistake, more rows in a radiator is no indication it will cool better. Mopar went from a 2 row to a 1 row radiator a year or two after the TJ was introduced and with that redesign better overall cooling was the result.

I replaced the fan clutch with hayden and reburped the system this morning. Still no difference. I believe the new aluminum radiator is just too thick to pull air through efficiently. I welded my old fan clutch solid and saw a huge improvement in cooling

I have a relatively stock cooling system and my Jeep operates in temperatures that routinely exceed 115°. Sometimes considerably. I can idle all day. As others have stated, radiator and fan clutch are the best starting point. Also, consider the coolant you used. I had a buddy buy a bargain brand that may well have been colored water. We flushed it out and put in a quality coolant and problem solved. I suspect his bogus coolant was a knock off. Something to consider, when these rigs were originally equipped with all stock parts, the rigs did not overheat.

Zerex G05 is what a lot of the experienced members recommend

 

[Jacob Boehmer]

Also found something very interesting. With my unmodified Hayden clutch, a piece of heavy thick paper will hold to the grille. Once it reaches operating temp (210F) or higher, it no longer holds the same paper to the grille. Very stumped on why this may be happening.

 

[Jacob Boehmer]

Let's go back to basics again !!! At a idle in drive way put a fan in front of radiator and see if temp drops,not a huge fan. If temp drops then you have a air flow problem, the air is not being pulled thru radiator. My guess is radiator, 2 row is harder to pull air thru clutch and fan designed for 1 row. You could add a electric fan in front if you wanted to keep radiator.

I definitely do have an airflow problem. I would like to keep the radiator as it has more coolant capacity and greater surface area than an oem mopar one which translates to better cooling as long as I can get adequate airflow through it. I have been scared away from an electric fan after reading about other members experiences with them. I know there are tons of threads on non oem style mechanical fans and clutches that “are better” but does anyone here have frst hand experience with them?

 

[Flivver250]

I definitely do have an airflow problem. I would like to keep the radiator as it has more coolant capacity and greater surface area than an oem mopar one which translates to better cooling as long as I can get adequate airflow through it. I have been scared away from an electric fan after reading about other members experiences with them. I know there are tons of threads on non oem style mechanical fans and clutches that “are better” but does anyone here have frst hand experience with them?

For a century, aeronautical engineers were absolutely certain a bumble bee was too heavy and their wings were much too small for the poor bumble to attain flight. Sometimes reality defies the claims of "translates to better cooling". If you are overheating at idle only, my first suspicion would be fan clutch as long as the waterpump was proven to be good. Would I be suspect of the "better" radiator? I'd let the thermometer be the judge.

 

[DETOUR]

I hope you found the cause ?
Vacuum filling is the answer IMHO