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Hope you all had a good Christmas.

Getting 1/3 litre coolant leak typically overnight.
Not leaking when running. ( Cornwall to London no loss!)
No obvious leaks from pipes or joints.
Rad looks dry
Evidence of red drops on underside near coolant expansion tank area, possible drops under tank near drain holes.
No pool of coolant on ground

Can't figure where the leak is or where the coolant is going.
Suspect possible crack in expansion tank or dose connection or is this a symptom of 'buflin' pipe?

Any ideas / suggestions as I'm trying to avoid the 400 mile round trip to Unit 20. (only because the distance, service has always been fantastic)

Thanks Ric

Are the under trays in the way of seeing where it is coming from? I'd pop them off first and see if it allows a better look.

Any garages with a ramp you can borrow and have a good look yourself? The small drain cam/borehole camera thingies are a useful tool as well. Might be able to get up into corners that you can't normally see into.

Hi ric.
As Suz said boroscope is a great way to find leaks in hard to get to places, some are really cheap to purchase.

I rebuilt my intake manifold towards the end of summer and since then I have a small coolant leak somewhere towards the rear of the engine. Like you, long runs are quite fine, but shorter runs that use more revs are an issue.
I can’t see from the top where exactly it’s leaking from and I’m not enthusiastic about working on my engine when it’s typically -10°c or colder outside. Best case scenario is that it’s the temperature sensor leaking as I can reach that from the top quite easily. But I guess it could also be a turbo pipe, which might be a nightmare. Guess I need to buy some ramp time and pressure test the bloody thing

Regards
Craig


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Usually the short coolant pipe inside the oil filter housing is the culprit of this kind of furtive leak. Unless you have a Bufkin / Poosey pipe.

Hi Ben
Can’t speak for Ric, but my bufkin was changed 4 years ago when my engine was rebuilt.


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Thanks for the suggestions.
Yes I've got the under-tray off and we had a very good looks around when it was on the ramp for an oil change recently.
of course now I talking about it, the leak as stopped!

Shop - yes was wondering if the buflin pipe might be the culprit?

Thankfully 111marc111 has fitted his bufkin pipe and provided feedback.
So I am now confident that we got all the correct sizes.

He said it was a bit tight on the O rings. Use some grease to facilitate installation. Original pipe had 2 x O rings.
These have 4 x O rings.
No interference with the brass. So that’s great news.

The original o rings on the bufkin pipe marc removed had flattened over time.