What do I have in my oil?

[eighty1toyota]

I have a 93 xj 4.0 187,000 miles and recently, as the engine warms up from a cold startup, the temp gauge will get up to about 225, then back to normal. It stays at 210 after that and has never overheated. I think that I have a bad thermostat because my upper hose stays cool until the temp gauge reads 225 and then the hose gets hot and the gauge goes back down. I also thought that I may have a leaking head gasket so I checked the condition of the oil on the dipstick. at the end of the dipstick there was a milky white liquid. The jeep had been sitting all night so I decided to drain the oil (thinking that if there was any coolant in the oil it would come out before the oil and I would know that I had a blown head gasket) so I drained all of the oil and there was no coolant or any discoloration to the oil. I pulled out the dipstick again and it still had white stuff on it. I kept cleaning it off and checking again and every time it was the same, even with the oil drained. I am stumped on this one? do I have a blown head gasket or is there something else contaminating my oil?

 

[Kejtar]

condensation in the disptick tube maybe?

 

[eighty1toyota]

I checked it last week, and then I checked it again this morning and the condition still has not changed

 

[RichP]

When the oil is new and the engine is cold you change it, then you heat the engine up and the oil gets hot. Then you shut it down and the engine cools off, sucks in cold moist air and you repeat again and again. Normally this is not an issue IF you allow the oil to reach operating temp and the moisture is cooked off in normal operation. When you do a whole bunch of short startups and shutdowns this process does not work, the moisture is never cooked out of the oil and you get a brown sludgy build up, usually also shows up on the the filler cap of most engines cept jeeps because the screw in vs having a hollow indentation like most caps...
It can take 20-30 min of operation for the oil to reach operating temp, try it, fire the engine up and wait till the tstat opens, then pull the dipstick and feel the oil, it will still be cold or at most warm but not hot... of course it depends on outside temps too...

As for the thermostat waiting till the last instant to open, thats fairly normal, some thermostats open gradually as they approach temp, some don't. My guess is that you don't have a factory OEM thermostat with the little bleed hole, otherwise you would get *some* coolant flow as soon as you started the engine.

 

[eighty1toyota]

That makes perfect sense, I have seen condensation on oil fill caps before and that is exactly what this looks like, but I drive 25 miles each way to work, in rush hour traffic. one drive cycle lasts 30-40 min. so why doesn't the condensation burn off?

 

[RichP]

Check your CCV system, that normally pulls alot of moisture out. I have a 98, 240,000+ mi and have been running Mobil-1 since breakin, never noticed this on mine. Daughter has a 97TJ and drives 8 miles to school, 8 miles home, again Mobil-1 and have not noticed it on hers or my sons TJ, he does 10mi one way to school and 10 back.

 

[eighty1toyota]

I checked the vent tubes from the valve cover to the intake. they seem to be ok, I did replace them within the past year. I still cant figure out how I am getting do much condensation in there. it never used to be like that.