oil in coolant '89 Jetta diesel

[briandownunda]

I have found oil in the coolant in the expansion tank.  Can I assume that this is from a bad head gasket or is there another way for this to happen ?  How harmful is this ?

Thanks in advance !

[Vincent Waldon]

Two other possibilities:

- crack in the block between an oil gallery and the coolant passages

- if your car is a turbo it has an water/oil heat exchanger... they can develop leaks

Compression test and/or leakdown test is a good next step if you don't have the water/oil heat exchanger.