XJ still overheats - have overhauled everything.

[lazyxj]

I think exhaust leaks near the block or transmission or both, causing overheating is a lot more common than people think!!!!! I could not see or hear mine either.

So, anyone have a good way of detecting hidden manifold leaks?
Maybe using an IR gun to look for excessively hot spots, especially near the oil pan?
Another tough to detect problem is a water pump with the wrong impeller (spinning in the wrong direction). They are available both direction, depending on what model Jeep and how the belts are configured.
Have not figured out a way of finding out, short of pulling the pump and comparing to the diagram in the FSM.

 

[Ecomike]

I like the IR near the oil pan idea!!!

I think somebody found theirs by accident recently using Seafoam. When they start the engine back up and it smokes from the Seafoam, they found smoke leaking out of a flange area.

So, anyone have a good way of detecting hidden manifold leaks?
Maybe using an IR gun to look for excessively hot spots, especially near the oil pan?
Another tough to detect problem is a water pump with the wrong impeller (spinning in the wrong direction). They are available both direction, depending on what model Jeep and how the belts are configured.
Have not figured out a way of finding out, short of pulling the pump and comparing to the diagram in the FSM.

I can tell mine is pumping hard by looking at my transparent Renix bottle (the one must people hate on, LOL) when I goose the engine. That tells me the pump is still working.

 

[fsupaintball]

I like the IR near the oil pan idea!!!

I think somebody found theirs by accident recently using Seafoam. When they start the engine back up and it smokes from the Seafoam, they found smoke leaking out of a flange area.

That sounds brilliant!

 

[mako my day]

Here is the tool I used. Now caution, it cost about 10 cents......


24" stick, with 3 pieces of dental floss tied to it, with a 2" mirror taped on the end. I stuck it down around the manifold, shined a flashlight onto the mirror, and BAM. The threads pointed directly away from the tiny little crack.

 

[Ecomike]

And make sure the e-fan is off during the test no doubt. I could do that with my Telescope mirror tool, easy.

Smoke generating Incense stick might work too.

Here is the tool I used. Now caution, it cost about 10 cents......


24" stick, with 3 pieces of dental floss tied to it, with a 2" mirror taped on the end. I stuck it down around the manifold, shined a flashlight onto the mirror, and BAM. The threads pointed directly away from the tiny little crack.

 

[mako my day]

Telescoping mirror would be perfect! I gots non of that fancy tooling at my house.

 

[fsupaintball]

Update to the thread -

I replaced my exhaust manifold this weekend. The old Thorley header had HUGE cracks. New good manifold seal, new donut flange seal, and I also installed a 97+ intake manifold. I also put in a 16lb radiator cap. It fired up just fine, and is much more quiet (no more manifold leak).

The damn thing still overheats on an interstate climb at 70 degrees.

I'm getting into "weird solution" territory now... I'll have a shop check the rad cap to make sure it's actually 16lb. I'll also have a hydrocarbon test done on my coolant to make sure my head gasket is OK (but the last compression test I had run came back fine...) After that... shit, I dunno, hood vents?? Maybe there's a way to test that the water pump moves coolant in the correct direction?

I'm not leaking any coolant. The aux fan kicks on at appropriate times. There's an amp under the passenger seat so I can't check if it's hot from a clogged cat.

I am ordering an IR temp gun. I could check the running temp of the cat and anything pertinent and tell you guys what it says... I don't know how hot that stuff is generally supposed to run.

 

[Talyn]

Thorley has a lifetime warranty.

 

[Shorty]

Another tough to detect problem is a water pump with the wrong impeller (spinning in the wrong direction). They are available both direction, depending on what model Jeep and how the belts are configured.
Have not figured out a way of finding out, short of pulling the pump and comparing to the diagram in the FSM.

The cooling system will always need the coolant to flow from the lower radiator hose to the water pump and all of the XJ 4.0L engines have the lower hose on the driver side. The only factor that would change is what direction the drive belt turns the pump. The XJ 4.0L has always used a serpentine belt that drives the pump with the back (flat side) of the belt. This routing method reverses the direction of the pump from the direction of the crankshaft pulley. Therefore, you will always want the reverse rotation impeller design for a stock belt drive XJ 4.0L.

The confusion comes into play when manufacturers catalog the pump by engine size and design instead of vehicle application. This pump also fits 2.5L and 4.2L Jeep engines that were available with V-belt drive systems and require standard rotation impellers.

hope this helps clear it up a bit

 

[fsupaintball]

Thorley has a lifetime warranty.

Good to know, thanks. I'm not the original owner but I might email them to see if they'll consider sending a replacement.

 

[Ecomike]

LOL, a 70 degree incline is pretty steep, LOL (JK)

What is the engine RPM at that point? Gearing, tires....

Update to the thread -



The damn thing still overheats on an interstate climb at 70 degrees.

 

[fsupaintball]

Kinda high. I've got 31" tires with 4.10 diffs, and I also downshift to 3rd for that section of the highway (65mph, high grade climb for ~4 miles). It's pretty extreme but I have a friend whose jeep (same year/model, but stock) runs pretty ice cold all the time, and it stays decently cool on that same stretch.

I think it runs around 3k up that stretch, but I'll pay more attention and report back.

I took this pic just after getting off the highway today. 68 degrees at the time, and I wasn't running the A/C. Both fans were active.

 

[mgeebxj]

Maybe this is a stupid question but have you confirmed your gauge readings with an IR thermometer?

 

[fsupaintball]

No but my "hand test" tells me "WAY TOO HOT"

There's an obvious difference in the engine bay from normal operating temp vs what I'm seeing.

 

[Ecomike]

Several thoughts, the lift, gearing, tires, and slope are all adding to the problem, and heat rises, so on a slope, and climbing the heat wants to move up, not down and out, and normal draft flow of air gets twisted and swirls under the hood. You need to make sure there are no paths for hot air to short circuit, or recirculate and that the fan shroud is intact. You may need a 3 row all brass CSF radiator and or some custom air flow work. I would check the Colorado guys and the MOD forum for ideas on upgrading the OEM cooling for your situation.

Stick shift or auto AW4?

 

[fsupaintball]

Auto. I already have a 2-row aluminum radiator. I'll check out the custom airflow option but that's not real enticing to me and I want to avoid spending a ton more money. Think hood vents would help?

 

[Ecomike]

Well the problem is one, hood vents tend to leak water on the TPS sensor and ruin them, two on a steep climb the hottest air wants to rise and role towards the highest spot, the front of the hood during a steep climb, and if possible get sucked back into the fan inlets. I know some of the mountain guys in Colorado chapter have fought this issue many times. I have not had to battle the issue. But I had to go to a three row brass CSF radiator and a ZJ fan clutch on my 87 just sitting in the driveway (with the AC on).

Since then, I upgraded the AC Condenser, replaced the AW4, and replaced the leaking exhaust flange donut that was leaking 1/2" from the oil pan :shiver: and got mine under control on flat lands in Houston Texas :sunshine:

 

[fsupaintball]

AC condenser? What does that have to do with overheating? I ask because mine is "noisy" and I have a replacement sitting here in a box.

 

[Ecomike]

AC condenser? What does that have to do with overheating? I ask because mine is "noisy" and I have a replacement sitting here in a box.

I was told old the serpentene condensers are not good enough for R-134a, the head pressure on the compressor gets too high, gets too hot, and draws more power, adding to the heat going from the condenser to the radiator. My AC works way better using a new 97 parallel flow AC condenser on my 87, R-134a converted AC. It got me about another 15 F cooler, and my AC works way better in crawling traffic in a 105 F heat wave day with out overheating the cooling system now.

 

[Got Jeep?]

Ecomike:
First off, thanks for some interesting answers that I haven't seen before. You touched on a few issues I actually have.
I have an exhaust leak somewhere near the manifold. I think it's the gasket. Would that really cause that much of an issue? Also as a side note, I have Thorley headers so I'm not sure if that affects temp, them being a possibly different material than the stock equipment.
I've never replaced the radiator cap.
Also, mud in the AC Condenser? I think mine has issues but probably not mud... it does make a loud, brief whine when kicking in sometimes. I think it's dying but it's too expensive for me to want to replace beforehand.

Sounds like you've got a/c condenser confused w/ a/c compressor. I've never heard a condenser "whine" when the compressor kicks on...