Coolant appears to be mixed with oil

1999 JEEP GRAND CHEROKEE
129,866 MILES • 4.7L • V8 • 4WD • AUTOMATIC
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JACQUELINE POUDRIER
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The coolant appears to be mixed with the oil in the oil fill cap. But not present at all on the dip stick. No oil in coolant reservoir or radiator.
The vehicle was running rough before replacing it with a brand new radiator, thermostat and transmission fluid. (I actually did not look to see if the oil was contaminated previous to radiator change.)
Vehicle is running great though no white smoke, no overheating, runs smooth.
Should I buy the kit to check for head gasket damage? I also have blue devil head gasket repair fluid but hesitant to use encase it is not the problem.
Mar 19, 2018 at 7:17 AM
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PATENTED_REPAIR_PRO
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I would stay away from any repair fluid because it really does not know where the leak is located, it just clogs everything including the tubes in the heater core and that brand new radiator and may not even clog up the head gasket leak.
I would though go ahead and use the combustion gas leak detector.
Are you saying that when you remove the engine oil fill cap, there is a milky like substance on the underside of the cap?
Mar 19, 2018 at 8:14 AM
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STEVE W.
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If you see only the crud on the cap it is more likely from moisture in the air getting into the engine and mixing with the crankcase vapor. I would start with draining the oil, any coolant will come out first as it will settle to the bottom. If you do not find any the next step would be to do a pressure test on the cooling system. If it holds pressure it is not likely you have a leak and the goop is condensation. (Pressure test kit is a loaner tool at many parts stores)
It is common to see that if the vehicle sets unused for a while or if it is not used for longer trips that get the oil hot.

If you are really worried you could do a combustion gas test, those are also a loaner tool (you pay for the liquid though).
Mar 19, 2018 at 8:23 AM
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JACQUELINE POUDRIER
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PATENTED_REPAIR_PRO
To your question. yes, there is the milky white residue on the oil cap and not on dipstick. no oil in coolant reservoir or in radiator when i removed cap.
Mar 19, 2018 at 8:16 PM
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JACQUELINE POUDRIER
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I bought the vehicle with visible radiator leak, put brand new radiator and thermostat. Complete oil change (did not notice any residue then) and then has sat parked and not operating for close to six months. I just noticed this residue when checking my fluid levels and topping off oil.
Mar 19, 2018 at 8:22 PM
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PATENTED_REPAIR_PRO
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Can you post a photo of the underside of that oil fill cap?
Mar 20, 2018 at 7:52 AM
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STEVE W.
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Setting for that long will build up condensation in the engine. When you start it up the water heats up along with any of the fuel vapor and other light contaminates in the oil. That circulates through the PCV system and will collect on spots that disrupt airflow.
Mar 20, 2018 at 12:38 PM
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JACQUELINE POUDRIER
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Phew...thank you guys so much for the helpful advice...very much appreciated!!!!!!
Mar 21, 2018 at 8:22 PM