Overheating - did some research but still need help

Alright, I've been using the FSM to try and get me through this, but I just can't put my finger on it.

Cheesy overheating lamp coming on (no guage).

Here's the stats:

1. '94 XJ SE w/ 121K mi.
2. March of 2001 the radiator was replaced with a Hotline radiator ( I dunno ).
3. New water pump
4. New belt (tensioned to 150 lbs)
5. New radiator cap
6. Coolant has 2 balls floating

I just replaced the water pump because the old one had a bad bearing and was whining anyway. The system is tight and there are no leaks. The Tstat is allowing coolant to pass because the upper hose is hot to the touch. The two heater hoses are hot. The lower radiator hose is warm but I can hold on to it without a problem. The auxiliary fan for the tranny fluid is working. I definately had a bit of air in the system, as I've had to top off the tank. But now I've had it out a couple times and it doesn't seem to be better. Also, I just replaced the belt and checked the tension.

Running the heat full blast helps but does not always get the light to shut off. Running up the RPMs in nuetral also helps.

I noticed that after a cold start and 4 miles of in town driving is when it starts to come on. In particular I've been making short runs to the store, and when I turn right it comes on immediately. I subsequently noticed that right hand turns seem to trigger the light to come on. But I may just be imagining all that.

The coolant has been replaced and should be good.

So good citizens of , I ask you, what's the next step and why?

TIA
Derek in MA

If its overheating when you are idling, check to see if the fan clutch is bad. Its pretty common. Good luck.

Did you replace the hoses and does the lower hose have the spring in it ??
Did you fully burp it ??
The thermostat, did it have a small hole in the flange and did you put that hole in the 12 O'clock position in the Tstat housing ??
I also second the fan clutch if it's original. Does it cool down on the hiway or stay hot ??

RichP said:

Did you replace the hoses and does the lower hose have the spring in it ??

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I did not replace the hoses at all. They look intact to me. The lower hose does have the spring and is not collapsing from suction. There is no significant bloating of the other hoses either.

RichP said:

Did you fully burp it ??

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I guess I don't know how to fully burp it. Since this is an open system, I was under the impression that it is self burping. The fact that I've had to fill up the bottle seems to be proof of that.

RichP said:

The thermostat, did it have a small hole in the flange and did you put that hole in the 12 O'clock position in the Tstat housing ??

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I've never replaced the Tstat. It is the orig, so there has been no change with that.

RichP said:

I also second the fan clutch if it's original.

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I've also never replaced the fan clutch. However, I don't think there is a fan clutch in this version. I have a fan that is mounted on a pulley attached to the serpentine belt, and hence it runs constantly and never disengages.

RichP said:

Does it cool down on the hiway or stay hot ??

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Since the car is now out of inspection, I haven't had a chance to take it on the highway to find out, however, as I mentioned earlier, running the eninge at higher RPM has produced some cooling benefits although it was limited.

Thnx for the ideas folks

Thermostats don't live forever I do mine sometimes yearly but at least every two years, one overheat can destroy a brand new thermostat. I also only use dealer OEM mopar tstat. It also has the correct bleed hole in it.
The mechanical fan that looks like it is mounted directly to the pulley *usually* has a fan clutch. To check this with the engine off see if you can turn the fan, if you can it has a fan clutch. I suppose a previous owner could have gotten rid of it and somehow bolted to the pulley directly but thats doubtful. The fan clutch is a big silver dish looking thing attached to the fan, it engages and disengages with heat so it's temp sensitive.
As far as burping the system that takes about 30 min or so after refilling all the coolant. It involves topping off the radiator, running the engine and allowing it to reach operating temp so the tstat opens, then when the level goes down in the filler neck you top it off again. I keep the level in the neck so I can see it. The air if it's not bubbling out looks like fuzzy green soda. As you run it the air will escape thru the open filler neck like soda goes flat in an open bottle. I also remove and clean out the overflow bottle really good then refill to the hot mark cause no matter how good you bleed it you never seen to be able to get all the air out.
The fan clutch is a good idea to replace, I will be doing my 98's in a couple of weeks after I get the AC fixed when I do my cooling system. I also use OEM dealer supplied one, on the 97+ the depth is important though there are some who use an aftermarket car quest one that is the same dimension. Consensus here is that the fan clutch and rad are good for about 5-7 years. Mine came with idiot lights and I just this past winter replaced it with a gauge cluster from a 97TJ so for the first time I can actually see the temp instead of dreading the 'red light' on the dash.

How much did you pay for the fan clutch? Mine doesn't seem grab hold til the engine's glowing red..

You might want to check the temp sender itself.located on the back /top conor of the head. The wire may be loose or the sensor broken.
Wayne

DeathByXJ said:

How much did you pay for the fan clutch? Mine doesn't seem grab hold til the engine's glowing red..

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OEM fan clutches are on the ~$70 area or so, depends on the discount your dealer gives you...

Do yourself and your Jeep a huge favour by getting rid of that idiot light and replacing it with an Autometer water temp. gauge. They're cheap, easy to install, and come with their own sending unit. Then you'll know exactly at what temp. your engine is running and it'll make troubleshooting a lot easier. It'll also give you an early warning of engine overheating and this could save your engine from major damage. The idiot light only comes on when it's almost too late to prevent overheating from damaging the engine.
If you only have an idiot light for the oil pressure, you'd be wise to install an oil pressure gauge as well.

I agree with checking the Temp. sender. I had dummy lights in mine and I just about drove myself nuts trying to figure out what was wrong with it. Turns out the sender was bad and the light would come on before the XJ even got to operating temp. and stayed while the truck was running. I decided to change the cluster with an actual set of guages out of an 89. Not exactly sure if that is possible with your 94, but I dont see why it would be that much different from my 90. You could go to the junk yard and find one from the same year and just swap them out. I had to change the Temp. sender and Oil pressure sender located on the distributor and the guages themselves and that was it. It was very easy to do and I was able to purchase all the parts for less than $120. The guages for my 90 ran $85, but it was well worth every penny. If you are considering putting in new guages, you might want to consider installing factory guages. But thats just my .02 cents. If anything, I would at least change the Temp. sender located on the back of the head. It might be the only thing wrong, especially if it is triggered by turning right. Good Luck!!!

90red

Here is another gauge option if you don't want to dig into the dash

http://www.quadratec.com/cgi-bin/sg...QA=1&UREQB=2&UREQC=3&UREQD=4&FNM=10&x=53&y=28

Quadratech also has a blank gauge pod that goes in the center of the TJ dash where the change holder is now, on top of the radio but it can easily be adapted to the XJ. Can't find the full catalogs and they are not in the XJ supplemental ones. whoda ever thought I'd have competetion for a jeep parts catalogs in my own house....

Thnx to all who posted. I will replace the fan clutch and Tstat/gasket in the next couple of days. I'll post the results.

On another note, I've wanted to replace the idiot lights and stupid gas/speedo cluster since I bought this heap. I always assumed it'd be a royal PITA, but a quick search showed me that it shouldn't be too much work. Once I get past this cooling issue, and get my lunchbox locker installed I'll look into that as a possible upgrade.

When was the last time the engine had a complete flush,you'd be supprised at the crap that builds up in the block.I try to back flush mine yearly,keeps the rad,the heater core,and the block clean.

Well, I resolved my overheating issue. I replaced the fan clutch and the tstat. I also rebalanced the coolant mixture ratio. I did the fan clutch first, but that did not resolve the problem. After I replaced the tstat and adjusted the coolant ratio it was all good.

The lesson learned here is replace the cheap stuff first.

Well, it's good to be back on the road once again.

Thnx much folks.