Coolant Expansion Tank Cap

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Carmo13
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Mon Nov 03, 2014 11:39 am

Hello,

My coolant expansion tank cap seems to be weeping a little, should the cap screw down onto a rubber washer?
If so then I must have lost mine at some point.

Many thanks
N-Gen
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Mon Nov 03, 2014 11:49 am

It should indeed have a rubber washer in the cap.
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Carmo13
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Mon Nov 03, 2014 11:52 am

Well I wonder where that has gone!

Thanks
N-Gen
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Mon Nov 03, 2014 11:56 am

The rubbers can easily slip out after they get worn.

This is what you need to be seeing.

Image
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Brianmoooore
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Mon Nov 03, 2014 1:42 pm

Flat rubber washer at the top has nothing to do with keeping coolant in. The O rings on the side are the pressure seals.
The cap in the pic. is from an iS, which uses a different (2 bar) cap from the 1.4 bar cap fitted to most other E30s. Unless your car is an iS, the original cap should have been replaced under a safety recall around seventeen years ago, which is still active. Most replacement caps have a yellow disc at the bottom instead of black, so if yours doesn't appear to have been changed, visit your dealer for a free replacement.
N-Gen
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Mon Nov 03, 2014 1:54 pm

That's some good info. Wish I've known about it before replacing my black ring one with a new yellow ring one.
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