Oil in Coolant A Guide to Identification, Causes, and Solutions

If you have oil in your reservoir you have a blown head gasket my friend. You can see it better in the reservoir then you can in the radiator. The coolant in a 5.3L Vortec does not communicate in any way with the intake manifold so a blown intake manifold gasket can not get oil into the coolant. Replace oil cooler. Fill cooling system w/ fresh water. Add a small(!) amount of detergent to coolant tank, run vehicle for a short bit. Drain. A leak between the oil containing part of the block and the cooling part is the only way that you can get motor oil in the coolant. The only thing that can cause it is a head gasket leak. You will need to have the engine pressure tested to see if the head gaskets are leaking. The oil cooler is leaking oil in the cooler system which is a common problem and the recommendation is to replace the oil cooler. Subaru oil in coolant, no coolant in oil, but how and why. Happy ... WHY COOLANT IS BOILING IN THE COOLANT TANK RESERVOIR ON A CAR. Auto ... However, pouring oil into an empty coolant reservoir is not advisable and should only be considered an absolute last resort in extreme ... They put a special cap on your cooling system and pressurize it, then monitor it for a period of time. if the pressure drops you have a leak somewhere. The only thing that comes to mind, is if the new reservoir cap is not venting properly, it could allow the cooling system to over-pressurize.