Hi,

I found some light oil in my coolant system and coolant reservoir. Oil is black in color. I thought it may had been a bad head gasket or cracked block so I took it in for a full test.
Compression Test: 210 210 205 205
Leak down Test: 5% 5% 8% 8%
Coolant Pressure Test: at 23psi, found no leaks.

The engine runs very strong for being a MY00 and barely burns any engine oil. We are both very confused to why there is oil in the coolant system and reservoir and my mechanic suggested it might be a defective factory oil cooler and have it tested.

Please share your suggestions.
Thanks!

 

Check the oil cooler adapter at the oil filter. It may be ruptured.

 

You can flush the cooling system and disconnect the coolant lines to the cooler. If you don't see any more oil the cooler is leaking.