Hi all, only just noticed there’s a thin film of oil on the inside of my coolant expansion tank. Above the fluid line. I managed to wipe some off and gave it a sniff, I think it’s diesel. Any idea where this be could from? The coolant itself appears fine, still very pink in colour with a few oily spots floating in it (so not heavily contaminated). Could it be from the Webasto heater, as I’ve been using that daily to pre heat the car. Any advice appreciated.
7th Feb 2022 9:26 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5052
No not possible from the webasto, probably the fuel cooler is shot.yµ (idµ - eAµ) ψ=mψ
7th Feb 2022 10:16 pm
sarumlight
Member Since: 06 Nov 2008
Location: Off the Plain
Posts: 1592
Are you sure it’s diesel? The oil cooler on mine went and the coolant was a disgusting mess by the time I noticed.
7th Feb 2022 11:08 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10689
There is a fuel cooler under the car by the starter. Easy to change.
There is another at the top of the engine, in the Vee. At the front. That’s low pressure though, so unlikely I guess
8th Feb 2022 6:20 am
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5052
The one alongside the starter is fuel to air cooled, so it has to be the one on top of the oil cooler which is fuel to water, assuming that is it's diesel you're looking at. If it's oil you're seeing in the expansion tank then it is likely the oil cooler itself which is also oil to water cooled.
This is the oil to water cooler in the vee which also incorporates the fuel to water cooler as well as the oil filter.
The other possibility is a head gasket weeping oil into the water jacket, but less likely.yµ (idµ - eAµ) ψ=mψ
8th Feb 2022 1:57 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10689
Odd.
My 2005 has fuel to coolant exchanger by the starter. (Fuel warmer I expect )
Not the first time I’ve heard it questioned though.
8th Feb 2022 4:59 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5052
Thanks for your replies. In fact I noticed this a few months ago, but just put it down to age of coolant. I guess the last time it was changed was when the cam belt was done. So probably due a flush etc. Anyway I took it to my mechanic today and said unlikely a head gasket, more likely a slight weep in oil cooler. Contamination in bottle not as bad as i feared. Looks bad from outside but once you shine a light in there it’s hardly noticeable. However no coolant loss, which I guess is a good thing, no scumming in the engine oil (still as black as ever) no power loss or performance issues.
Mechanic will do a coolant flush next week, change coolant expansion tank then see where we go from there. Cheers everyone. Ps mine is a late 2016 model. 66 plate. Will a replacement oil cooler be the same across the D4 range?
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