I have a 98 Lincoln Navigator and I have a problem where my motor oil got into my radiator water reservoir and I checked the motor oil and it's clean

there is a chance that the transmission oil cooler in the radiator failed. that would be the easy fix. if you are sure it is motor oil, then you most likely have a bad head gasket. have a combustion leak test done and it will tell you if the head gasket is bad. hopefully, if it is the head gasket the head itself isn't cracked. Lets all go home tonight hoping for you that it is tranny fluid and the tranny cooler is leakin. good luck.

It is motor oil because I have been putting motor oil in the motor more often than usual so am sure it's motor oil because it also looks like when you add milk to a cup of coffee and if it was transmission oil I think it would look red wouldn't it?

Yup, sounds like oil. Get that combustion leak test done and see if it is a head or head gasket problem. There are some good videos on you tube or if you don't feel up to it, take it to a pro.

How do I get that done the combustion leak test?would I be able to do it myself or do I need to take it to a shop to get that done?

There is a kit from Napa, or whatever store you like, that is about 40 bucks. It involves a clear tube that you hook to your radiator cap hole. You put in the blue test fluid an run the car. You want to be able to pull air through the fluid from the radiator with some kind of a little vac bulb that should come with the kit. There again, search you tube, there are some good vids on the procedure. I would at least call around, and see what a mechanic charges for the test. If they will do it for40 or 50 bucks, why put yourself through it.

Thank you I will do that I really appreciate your suggestions thank you again

How would motor oil get into the coolant and not the other way around? I know coolant in the oil is head gasket. Never heard of the opposite happening? Just curious?

Did you ever fix your problem?? I have the same issue