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Discussion Starter #1
I bought my rubi used and it looked like someone had mixed different kinds of coolant and it was all mucky. The coolant reservoir looked like it had 4 inches of mud in it from the mixing. I did a flush with the flush and fill kit. Afterwards I put 1 gallon of the red mopar coolant and the rest water. That is what the guy at the dealer said do... Its not quite 50/50, but he said its fine in this climate. I went offroading and it is overheating when not getting air on the street. I have heard that it could be air pockets. I took the cap off and tried to vent it and I also added more coolant to up the ratio a bit. It is still overheating, but not loosing fluid. Any ideas? It is not under warranty.

Thanks.
 

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Check that the radiatior is not cloged with mud, that the fan is pulling air (fan clutch), Might have stuck the T-stadt with the flush, but I doubt it.

4xcontractor
 

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Your jeep had a coolant leak somewhere and the previous owner dumped that mud stuff in as a bandaid fix. You can buy it at any auto parts store and it usually works for a while, but be on the lookout for leaks. I used it on an old van once that had a head gasket leak - the stuff looks like small beads of dark black mud in a dark brown liquid and is sold under many different names as a radiator/coolant leak fix. It fixed the leak, but left the mud in the reservoir and I'm sure the abrasive fluid is not good for new engines with aluminum heads. Mine was an old cast iron chevy 350 cid engine. Get it professionally flushed again - and make sure your fan by the radiator is working as well. Good Luck.
 

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Sounds like it had a dose of "Bars Leak" sealer dumped in it. I consider that stuff an emergency measure only but I do carry it.

Make sure the cooling system is pressurized. After the engine is hot wrap a rag around your hand and squeeze the upper radiator hose. If it is squishy the system is not sealed, it should have pressure in the hose. If the system is not pressurized it will boil at a temperature about 30 degrees lower than when pressurized.

A logical first place to look is around the aluminum/plastic crimped seal on both the top and bottom of the stock radiator. If you find a leak, it means you need a new radiator, not "Bars Leak".

If you still think you have air bubbles get the Jeep's nose as high as you can. I use ramps on my sloped driveway, and drive up the driveway and up the ramp. The idea is to get the radiator and cap higher than any part of the engine and radiator hoses. Then when you rev the engine, the air bubbles go to the top of the radiator under the cap, and are eliminated when you top-off.
 

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Discussion Starter #7
Thanks for all the advice guys. I replaced the T-Stat today just to rule that out. I will do the air bubble thing tomorrow.
 

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Discussion Starter #8
OK, after replacing the thermostat it is not overheating anymore. However, when I tried sqeezing the upper radiator hose like the poster above said, it was squishy. So I guess I am not holding pressure. Any ideas on how to check where the leak is?
 
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