Found some engine oil in my coolant expansion tank last week and been flushing the system out. There's a slight layer of "mayo" around the inside of the coolant expansion tank which I'll need to clean out. Read online to use dishwasher powder and simple green, so will give that a try. Engine oil looks like oil, no signs of mayo in that.

I'm assuming head gasket but a friend mentioned it could be the oil cooler. I just wondered if anyone has ever come across an issue with the oil cooler?

Any other suggestions?

Cheers

Vijay

Much more likely to be oil cooler.

21 minutes ago, Breezy_Pete said:

Much more likely to be oil cooler.

Cheers Pete. Are the oil coolers a known issue then? I used the search but it came up with nothing

The site search isn’t great, better to use a Google search, specifying site: briskoda.net

As for the cooler, well it’s a much less painful point of failure than the head gasket being gone… so worth the hope.

I do vaguely remember (when the mk1 section was busier) there having been a number of cooler leaks. So not uncommon, esp bearing these cars’ ages now…

14 hours ago, Vijay2018 said:

Cheers Pete. Are the oil coolers a known issue then? I used the search but it came up with nothing

Not sure which engine type you have, but I based my comment on the fact that the single high-pressure oil feed that goes from block to head in most engines tends to be alongside or even coaxial with one of the headbolts. This means it is relatively unlikely to communicate with a water channel if the gasket does develop any leakage. Water channel into oil return (causing water into oil, not the converse because of the pressure relation), or across fire ring into cylinder will be much more common gasket failures, by a large margin.

Oil coolers, as mac says, are way cheaper and easier to swap; and tend to carry pressurised oil in close proximity to coolant, which may have eroded/corroded the pipework over the years.

Edited 24 July, 202524 Jul by Breezy_Pete

10 hours ago, mac11irl said:

The site search isn’t great, better to use a Google search, specifying site: briskoda.net

As for the cooler, well it’s a much less painful point of failure than the head gasket being gone… so worth the hope.

I do vaguely remember (when the mk1 section was busier) there having been a number of cooler leaks. So not uncommon, esp bearing these cars’ ages now…

Cheers mate. Just tried it and much better, but strangely didn't find this post...............

I'll order an oil cooler this morning and hopefully get a chance to fit it next week

29 minutes ago, Breezy_Pete said:

Not sure which engine type you have, but I based my comment on the fact that the single high-pressure oil feed that goes from block to head in most engines tends to be alongside or even coaxial with one of the headbolts. This means it is relatively unlikely to communicate with a water channel if the gasket does develop any leakage. Water channel into oil return (causing water into oil, not the converse because of the pressure relation), or across fire ring into cylinder will be much more common gasket failures, by a large margin.

Oil coolers, as mac says, are way cheaper and easier to swap; and tend to carry pressurised oil in close proximity to coolant, which may have eroded/corroded the pipework over the years.

1.9 ASV

changed the cooler today. Not a bad job apart from the nut size which was bigger than 24mm (largest I have). I ended up using a plumbers basin wrench, which allowed me to undo it at an angle and grip the large bolt.

Will pressure test the old one when I get 5 minutes to see if there was a leak.

I'm hoping I have a oil cooler issue again and not the HG. I wondered if it was ok to bypass the water side of the oil cooler for a short while and see if I'm still getting oil in the coolant?

What damage/negative effects would I have if the coollant side of the oil cooler was bypassed?

Cheers

Vijay

You mentioned a dishwasher tablet to clean out the cooling system?....did you do this?

Reason I'm asking is I had major oil contamination in my Audi (1Z) from what I assumed was the oil cooler, changed the cooler and flushed everything through with a hose-pipe but never actually used any chemical flush. I seem to get an oil residue in the expansion tank every now and again, I think it's just oil that's been trapped somewhere in the water jacket.

Maybe I should stick a dishwasher tablet in it ?!! It doesn't bother me, car runs fine .

I did many times and it cleaned things up before. I think without something to break down the oil, couldn't see how cold water from a hose would flush any oil out

9 minutes ago, Vijay2018 said:

I did many times and it cleaned things up before. I think without something to break down the oil, couldn't see how cold water from a hose would flush any oil out

It's all I had at the time I replaced the cooler.

Best of luck 👍