Oil and bubbles in expansion tank, but no CO2

[Globalnomads]

Hi all,

I have a query regarding what I thought was a head gasket failure but I'm now a little confused after a CO2 leak test.

I have small bubbles in the expansion tank which increase in intensity as the revs increase and there is a very small change in coolant level over time, but nothing major.

Also, I have noticed recently the appearance of a small amount of oil in the expansion tank. However, there is no signs of water mixing with the oil on the dipstick.

I first thought...head gasket for sure....however, I bought a CO2 leak test kit to be 100% and after the test the solution remained blue indicating that no CO2 was present in the cooling system.

Does this test confirm that the head gasket is ok and the fault is elsewhere? Or could the head gasket have failed but CO2 is not passing into the coolant system?

There is no white smoke from the exhaust or coolant smell coming from anywhere, I was just surprised as I thought it was the gasket until the leak test. The only change recently in the engine bay is the radiator, but I don't have any issues with temperature at all.

If anyone has any thoughts on this it would be greatly appreciated.

Many thanks,

Dan

[BilboBoggles]

Which engine?

[digger]

oil seal on oil cooler.... I had a lot of oil in the coolant exp. bottle but nothing apparent waterwise on the stick!

(mine is hopefully being finished on Monday)
mine is 2.2 mtr (puma)

[Globalnomads]

Firstly, to all the Dad's out there. Happy Father's Day today, I hope you have a great day.

BilboBoggles and digger, thanks for the replies.

The engine is a 300Tdi engine.

Regarding the oil seal on the oil cooler, I will have to check this digger. However, I thought the oil cooler was integrated into the radiator, so how do I get to it to inspect, repair or replace?

Cheers,

Dan

[Globalnomads]

Another thought regarding the oil cooler......

Is it possible that a failed oil seal can also contribute to the bubbles in the expansion tank? Or is this likely to be a separate issue?

Cheers,

Dan

[PAT303]

Mine does the same,it's from the water pump pushing coolant back up the pipe from the thermostat,I can rev mine and it pumps coolant out of the tank. Pat

[Globalnomads]

Thank you for the reply Pat.

So how did you go about rectifying the water pump issue, and what do you feel is the cause of the coolant being pumped back to the expansion tank?