GQ 4.2 Oil in coolant overflow tank

[maxalby]

GQ 4.2 naturally aspirated 1994 manual diesel. 407000 kms. Runs very well with negligible oil usage between changes.
Oil is appearing in the coolant overflow tank, but the vehicle is not overheating, is not losing coolant, and there are no air bubbles apparent with the radiator cap removed.
A strange one and I'd welcome any suggestions as to the possible cause(s) and solutions.
Thanks.

[4bye4]

G'day mate and welcome to the forum. Head gasket leaking between the water port and oil return port??.

[nipagu7]

i'd say headgaskt to. if you remove the radiator cap and tape a clear plastic bottle with the bottom cut off on top of the opening and pour water in till it comes slightly out of the radiator then start the motor. allow a bit of time till any trapped air comes out. then see if any bubbles come out. there is also a test kit that i believe you can get, that you can test the radiator coolant with. i think it tests for Co2 but i've not had any experiance with this myself.

[GQtdauto]

Yep head gasket at best .

[Deano2506]

Just a thought but could it be oil cooler?

[AB]

Just a thought but could it be oil cooler?

Definitely possible O'ring perished. Can't believe the oil cooler housing shares the water ports with 2 x O'rings sealing everything apart.

[maxalby]

Many thanks for your replies. My first thoughts, of course, were a head gasket problem and I also wondered about the oil cooler. I've got a Gregorys GQ workshop manual and there is a section on the dismantling and re-assembly of the oil cooler.......looks like access could be pretty difficult. But first, I'll need to make absolutely certain it's not a head gasket problem.
Thanks again.

[Jdbwhiskey]

Hi, wondering if you ever figured out what the issue was? I too have oil in my coolant😬

[First Pooy]

Oil cooler over head gasket, plus the cooler is an easier and cheaper job then the head gasket and if you have more then just a bit off oil in your expansion tank then that points to oil cooler again.