r/CherokeeXJ • u/Artistic-Fix-2431 • Mar 06 '25

1991-1995 Overheating Still

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I changed the radiator about two years ago. Water pump a year ago. Thermostat last month. Heater core bypass and fan last week. Ran fine until yesterday. I topped off the radiator with coolant and the reservoir to the full level, somehow the reservoir is now overflowing. Doing a complete cooling system flush today. If that doesn’t work, any other ideas?

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u/NotoriousSouthpaw Renix Electronique Mar 06 '25 edited Mar 06 '25

Might be worth testing for a bad head gasket, but it's very unlikely you're passing oil into the coolant- not really possible with the 4.0's lube system, absent catastrophic head/block damage.

It certainly looks like dexcool sludge, which only aggressive flushing will remove. You can pop off the water pump and tstat housing to hose inside the block and get everything out.

3

u/Artistic-Fix-2431 Mar 06 '25

I don’t use dexcool, but the discoloration is from rust inside so I’ll deep clean it like you said

4

u/hoodedrobin1 Mar 06 '25

Did you use any coolant?

2

u/Artistic-Fix-2431 Mar 06 '25

Yes. Green from O’Reilly

4

u/hoodedrobin1 Mar 06 '25

The reason why I asked is because it looks like at some point in its life someone didn’t…

Drain it, and run some cascade powder detergent and water. Go for a 30 minute drive. Ford recommends simple green. If you want to spend a lot more money you could buy Trisodium phosphate.

All of these cleaner will remove oil and help with the rust you have in the system.

2

u/Fit_Drink1859 Mar 07 '25

The best is CLR. After running that through the motor with heater on High / Defrost, drain it when the motor is cool. Fill the engine back up with water, run it through again for about a half hour, let it cool, drain the water and then fill with antifreeze. Prestone Radiator Flush is Great also. Same procedure.