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Overheating troubles

UltimateG

NAXJA Forum User
Location
Tahoe
Hi,

Before now, I’ve never had any problems with the cooling system in my jeep. Even on the hottest days, she would stay under 210 degrees. But for the last year, my radiator has had a minor leak that would cause a little coolant to come occasionally drip out. So, I recently replaced the original single row radiator, and installed a two-row all metal model from CSF. I also cleaned/flushed the cooling system, put in a new thermostat from napa and added 50/50 prestone coolant.

Now she’s running hot sometimes, and I can’t tell why. Most of the time, it still runs at the normal 195 degrees, but when driving through the mountains, or highway driving on very hot days, it’ll creep up to about 230 degrees.

What went wrong? Could it be the new radiator? Bad thermostat? Did I do something else wrong?





1994 XJ, 4.0 Automatic transmission. Daily driver, completely stock.
 
Read this from FlowKooler FAQs: http://flowkooler.com/cooling_faq/

The thermostat is supposed to start opening at a set temperature, then fully open as the coolant temperature increases until it is fully opened. If the vehicle should cool down the thermostat will close again to raise the coolant temperature in an attempt to keep the engine running at its designed temperature--which is higher than the set opening temperature.

Do you have an auxiliary electric fan? If so, is it functioning at all?

When was the last time you flushed the transmission fluid? Transmission slippage generates heat, and lots of it.
 
When was the last time you flushed the transmission fluid? Transmission slippage generates heat, and lots of it.



I’ve never done a flush, but once or twice a year, I pull the plug, drain three quarts then refill. But, I’m not too knowledgeable about these things, would Y’all mind giving me some advice regarding ATF?

I just checked today and found the fluid looking pretty dark. It seemed nice and red on the dipstick, but when I drained it into a bucket, it was very dark maroon colored. (but not black, and didn’t smell burnt at all) Is this bad?

-also-

At the start of the summer, I added 3 quarts of Dex/Merc. Since I put it in, I *sorta* had a feeling that the shifts weren't quite the same as before. But there wasn't really a noticeable difference, so I just assumed that I was being paranoid. Now I'm not so sure.

So, now I'm wondering, did I put in the wrong fluid? Here’s what I used:

atf-1-1.jpg
 
Dex/Merc III is correct, you can move up to Dex VI, it is backwards compatible.

The original Dex II/III was good for about 30k miles MAX, and overheating would reduce the life substantially. You have been diligent in changing a little at a time--full flush is about 13 quarts--so I'm a little surprised it would be dark.

Were you using a different type of fluid before you added the Dex/Merc?

As to heat--love Tahoe by the way--you can run 30 ethylene glycol/70 distilled water when its not freezing, say late Spring through early Fall in your area.

You can upgrade to a ZJ HD fan clutch, NAPA 272310 for the 97-98 4.0 in the ZJ, $44, and a direct bolt in replacement. You have to get it through NAPA, the other parts stores will sell you something else they claim is a crossover part--it won't be. Also, you don't want the ZJ MAX COOL, it won't fit. NAPA 272310 if you decide to do it.

You could consider a transmission auxiliary cooler, mounts in front of the radiator. If you decide to do this the best are the "plate" type, and you can often times source one from a salvage yard off a different make vehicles.

Do you have an auxiliary fan? Need to check and verify it is working.

When was the last time you replaced the radiator cap? About two years on those, never mess with the lever-release type, and tell the counter dude at the parts store you want a 16 lb cap instead of the 13 lb cap they will try and sell you. Those extra 3 lbs makes a difference in the boiling point of your coolant. Pressure raises boiling point.

Post up what you end up doing.

Good luck.
 
How's your A/C condenser look? Every now and then I'll pull up a chair, pull off the grill and use a dental pic to clean and straighten out the fins on mine. All kinds of crap gets wedged and driven into those fins, being out front. Can make a difference. Though not always obvious, some get so bad that they should be replaced.
 
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