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Navarrotruckinginc · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

hey guys couple weeks ago I noticed a film of oil on the top of my radiator Reservoir so I flush it out cleaned no oil for about 2 weeks then film appeared again.so wondering if its oil cooler seal or its the oil cooler itself.help?

Rawze · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

(01-31-2017 )Navarrotruckinginc Wrote: hey guys couple weeks ago I noticed a film of oil on the top of my radiator Reservoir so I flush it out cleaned no oil for about 2 weeks then film appeared again.so wondering if its oil cooler seal or its the oil cooler itself.help?

The oil cooler is usually the most likely culprit on them. When the engine is running, the oil pressure is higher than coolant pressure. This means if there is a leak in the cooler, oil ends up in the coolant. After the engine shuts down though, there is usually pressure in the coolant system but no longer in the oil system. This means that coolant gets back into the oil too.

Hammerhead · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

If you have a liquid cooled transmission, then I would suggest you pull oil samples of both your engine as well as the transmission and have them tested. Specifically telling the lab you are looking for coolant intrusion. If you can scrape a decent amount of the oil emulsion from the rad tank, send some of that along as well to confirm which type of oil it is.
The hell you say Hammer!
I know, if I hadn't had it happen to me, I'd be really skeptical as well. A couple years back I had some oil show up in my rad as well. For some reason it didn't appear as engine oil, my inframe was just under a year old, and I just thought it was odd. I pulled samples from the engine oil, tranny (liquid cooled), and my APU (cause it's tied into the coolant system too), and scraped a bunch of the emulsion from the rad. Low and behold, it was transmission oil. The tranny sample came back with such small traces of coolant, that if I hadn't specified what I was looking for, it may have been overlooked, they tested it three times to confirm. When the emulsion was analyzed, there was one additive quantity that only matched the tranny. The lab emailed the results & called me to verify, transmission. I would have never thought the transmission being as low as it is, not pressurized that it could actually force oil into the coolant side of the tranny cooler, but it did.

Johnboy · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

That's no joke on the transmission oil,check the oil in the transmission if its milky looking that's a problem the internal coolers are notorious for leaking. I went thru two transmissions in three months both due to the cooler the third was an air cooled trans that took care of the problem. Keep in mind if it leaks one way it can go the other.

Brock · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

Easy to differentiate between engine oil and transmission. Tyranny oil will have a greenish color and the coolant will turn to sludge, engine oil will have your reservoir turning black from soot weather you have @m*m^2 and clean oil or not.

Navarrotruckinginc · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

Thanks guys I'm on my way to look at the coloration now I believe it's more of a blackish color but not completely black now if it is greenish from the transmission fluid what would that be the same as replacing the oil cooler itself to fix that issue

Navarrotruckinginc · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

(01-31-2017 )Brock Wrote: Easy to differentiate between engine oil and transmission. Tyranny oil will have a greenish color and the coolant will turn to sludge, engine oil will have your reservoir turning black from soot weather you have @m*m^2 and clean oil or not.

Hey buddy I have a question if it is the transmission fluid going into the reservoir

Nilao · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

The transmission cooler is part of the radiator. If it leaks you have to replace the radiator or convert it to an air cooler and put pipe plugs into the cooler ports on the radiator.

Rawze · 01-31-2017, **(Subject: oil in my radiator Reservoir )**

(01-31-2017 )Nilao Wrote: The transmission cooler is part of the radiator. If it leaks you have to replace the radiator or convert it to an air cooler and put pipe plugs into the cooler ports on the radiator.

Every truck is slightly different. Some are in the tranny itself, some are in a heat exchanger on top of the tranny, some are air cooled only (like mine), some are in radiator.