Motorcycle Repair: Oil / coolant mixed, coolant pump, engine seals

Question
Chris, I own a 2004 GSX-R 750.  Last fall the engine overheated, with an Oil/coolant mixture overflowing through the radiator overflow.  I initially thought that the head gasket was to blame, however after pulling the head from the motor, I found it in great shape.  The head also looks good, as far as I can tell.  I see no warping on the head nor the block.  The oil in the oil pan and filter has no coolant in it, however the rest of the motor had a mixture of oil and coolant.  Any ideas of what else could have caused this? or where I should look for a failure?


Answer
Hi Richard.

Any time that you have oil in the coolant or coolant in the oil, you have a leak in an internal engine seal.  Unfortunately, this is a problem that you can run into anytime you have a liquid-cooled engine.

The most likely culprit is a failed oil seal in the coolant pump.  That is not as bad as it sounds, since coolant pump seals are a lot easier to replace than deep internal engine seals.

Let me know what you find.

Good luck and ride safe.
FALCON