I have read thread after thread about overheating and can't quite find my situation. So here goes.


2001 that had never had any real maintenance done on the cooling system. Overheating regularly. (no the head isn't cracked ) yet...

It was gushing tranny fluid when hot.


I replaced the fan clutch, water pump, t stat, radiator and radiator cap with OEM spec units and flushed transmission.

Overfilled transmission..

I tried and tried to over heat this thing for a month. Couldn't do it. Never got about about 220 and that was only when it was hot outside and running it like a race car up a 8% grade. Still some blow by from the transmission which is to be expected with overfilling it.




Today I get the AC serviced (haven't had AC in a couple years) and when I get to the top of the 8% grade, normal driving, the tranny is puking fluid from the breather and the engine is overheating.

At the top of the Mtn I stop and make a right turn to go to the house.

As soon as I stop to make the turn my check gauges light comes on and I see I'm at 260 degrees.

Whenever I was overheating before it was when I got to the top and stopped to make the right. Almost as soon as I slowed down the temp would spike.


Popped the hood and everything is spinning as it should, mech fan is on, electric fan is on (might not sound so great so maybe THATS the problem?)

No fluid loss, fluid is nice and clean...

So what? Since the e fan is the only thing not replaced (other than heater core) that might be it?

I'm pretty certain the heater core is good as when it gets hot I can turn the heat wide open and the temp comes down quickly.


I know I know...

A billion threads about overheating... Sorry guys...

 

So you tried over and over to kill it, and when you finally succeeded you ask why? lol how are you so certain you haven't blown the gasket/head? Check the oil to see if it is milky. You do have the 01' with the bad head and it takes just one overheat to find that weakness. I am not familiar with the tranny much but are you burning the fluid or just have too much in it? I think those are two separate issues.

 

LOL I got ya! No, the AC was what was different this time.

No milky oil, loss of pressure, junk in filler cap and have had an oil analysys done and all come back clean.

For right now I'm calling myself lucky on the cracked head part.

But back to the heating issue. This was the first time I have run the AC in years and it heated right up.

The transmission fluid spewing has me wondering too...


I'm about at the end of my diagnostic ability and am just replacing parts in the hopes of fixing it. It's getting expen$ive...

 

1. If you have an overfilled transmission, you MUST resolve it. Don't count on the transmission to expel the extra fluid. Too much fluid results in "aeration" of the fluid which reduces the lubrication qualities. It is also tough on transmission seals. Fix this ASAP.

2. The e-fan should come on at approximately 217 degrees. If it is doing that, the fan is not a problem.

 

Your head is probably cracked internally where it can't be seen.

When you buy a head, either get a TUPY which came after yours, or get a brand new one aftermarket.

 

Well, I thought it would correct itself... Ok, draining a little fluid won't take long, I can do that.

 

Ok, I understand the 0331 heads are prone to cracking. I get that.

BUT there are thousands of pre 2000 XJ's with overheating issues not related to a cracked head.

I am going to avoid swapping heads until all other options have been explored.

I may very well have a cracked head. But I may very well not. And once everything else is done and I have to replace the head then I will at least have a new cooling system to protect it.

If I fix the problem before it gets to that point that's all the better.



Now lets assume it's not the head. What would be the next step in diagnosing my issue?

 

since the heater core is the only thing you haven't replaced with the cooling system, could it be blocked even though you flushed it? Is the belt slipping once the ac is on, not allowing the coolant to flow proper? You could have a bad pump even though you replaced it.

 

The heater core concerns me. The belt doesn't slip.

When I turn the engine off I can hear coolant gurgling under the hood.

Still, the transmission thing has got to be related though doesn't it? Since it started with the overheating issue and only does it when it gets hot.

I thought the overfull thing was the culprit but as I type and think about it theres just to much coincidence.

 

Get the transmission to the correct level. It has to be done regardless.

The heater core is usually not involved in overheat issues.

 

Roger that...

 

I assumed we were throwing "usually the problem" out the door once the entire cooling system has been replaced. If the system was really gunked up and flushed incorrect it could have plugged something up like the heater core. I don't know how possible that is, or if it would even matter.

I still say the head is worth checking. Figured I could throw some much less likely possibilities out there if you wanted the head out of the picture

 

I gotcha. This is my DD and my only vehicle. Cracking the engine will be a PITA.

I guess I'm looking for more of a flowchart kinda answer. Try this then that, if this happens do that.

And hoping there is something obvious in front of me that I'm missing.

UGH...

 

You threw money at everything on the flowchart before the head comes up

usually you check fluids, fans/shroud, exhaust for white smoke, then cooling system components. If none of those are the problem, you move to the head. I am not sure if a compression test works for all types/location of damage but look into that before you rip everything apart.

Also, have you verified the engine temp is actually that high? Since the efan is kicking on i would still say yes it is, but since it works off the same sensor I don't know. Maybe someone else could chime in and say whether or not a bad temp sensor can send a false reading to the gauge, fan, and computer?

 

Ok, I can do that. I have access to a IR temp gun. Ill aim it at the tstat and see what it says.

I'm chatting with my brother (builder of 600 and 700 HP Subarus) and mentioned Ive seen the new lower radiator hose collapsed at times. He suggested vapor lock causing an issue...