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Polyproplylene master cylinder caps

Tim Hunt

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For many years I was plagued by a rust coloured corrosion on the master cylinder threads, which required cleaning off at regular intervals. Some time ago I replaced the clutch m/c cap with a plastic one and this solved the problem.  These smaller plastic caps are widely available but until just now I had been unable to find a similar  plastic replacement for the larger brake m/c cap of approx 63mm i.d.(original alloy cap is Girling part no.510844). I received a tip off (thanks to Kevin Fielder 'Box of Bits') that such a cap is now available from Upgrade Motorsport (see link below) and duly ordered one for the princley sum of £4.95 (note that a replacement alloy cap is currently £20 plus delivery from Moss). I can report that the cap is vented and fitted perfectly as a direct replacement for 510844. Hopefully my days of regularly cleaning the brown mess off cylinders and caps are now over. The plastic reservoir caps in my car would probably offend the purists but then so would much else, it's never going to be a concours candidate - i enjoy driving it too much.



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Ah Tim! This is brilliant, I searched high and low for a poly one for large Girling MCs long ago and gave up. I too have a smaller one (mini fit with level sensor) already. 

I checked the Amazon link, and they had gone up a couple quid. Searched for the actual website and just bought one on there for just under £4 delivered: https://www.upgrademotorsport.co.uk/product-page/girling-type-brake-fluid-reservoir-cap-motorsport-classic-car-4x4-uk-seller

Will report back re fit. Thanks for the tip! 

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8 hours ago, Tim Hunt said:

Thanks for telling me I did 95 pence in cold blood Ben! But seriously, I'm glad I was able to help you out. 


Hah, sorry. I just didn’t want anyone else to pay what Amazon are asking now. They probably have it on the automatic pricing thing based on clicks and interest. 

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Honestly I'd have paid a tenner, it's always such a pain getting the alloy one off, I think every time I'm going to snap the main body/pedestal.

I'd quite like to modify it to include the level warning switch from a mini brake MC (GRK6009 / AEU1796), then wire both MCs to a little warning light. Just because 🙂 

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