Clutch Master Cylinder as Brake Master ??

[Greta]

Just a quickie

I'm trying to fix a leaking Brake Master Cylinder prior to a MOT - I've had limited success in servicing them in the past ... ended up with binding brakes as the piston chamber would never completely depressurize. Anyway - I have three spare brake master cylinders - non of which fit my MKIII Spitfire without fouling the corner of the wiper motor - after market replacements all seem to come with a huge plastic reservoir. - They won't therefore seat flat on the bulk head. I see no quick way of fabricating a modification to the Wiper Motor mountings without radically altering the alignment of the activating mechanism.

However, I do have a large bore clutch master cylinder ... although the reservoir is smaller than the standard BMC ( it therefore fits !! ) am I legal to use this - or will such a set up also fail an MOT ??

[Nick Jones]

From memory, both clutch and brake m/c’s on the Spit are 5/8” bore, so a straight swap in that respect. The smaller reservoir is not ideal as (unlike drums) the caliper fluid volume increases as the pads wear down, causing the the level to drop in the reservoir. In reality this is absolutely no problem on a properly maintained car where the fluid levels are regularly checked. I would be amazed if the MoT man cares or even notices.

Also, you can get reservoir extensions that screw onto the top and increase the depth.

[Greta]

Thanks Nick - I'll give it a go - the car is new to me and I'm expecting a few fails and advisories but good to do things I can spot. It's a fairly easy way for me to create a "job list" ... expect a few more questions !

[2.5piman]

Hello Greta,

 many after market cylinders come with remote reservoirs, so that is another option?

Alec

[122344]

https://www.amazon.com/Wilwood-260-2636-Master-Cylinder-Girling/dp/B003XVEFHC/ref=sr_1_1?gclid=CjwKCAjw8e7mBRBsEiwAPVxxiA80ml26DHBuluxjToVMiLRGOEM8LBldrXJIZhLzUObG7HSC-7buhBoCrCcQAvD_BwE&hvadid=253496469582&hvdev=c&hvlocphy=9002229&hvnetw=g&hvpos=1t1&hvqmt=e&hvrand=5399091468700986628&hvtargid=kwd-423710107655&hydadcr=5741_9590435&keywords=wilwood+5%2F8+master+cylinder&qid=1557976094&s=gateway&sr=8-1  these are reasonably priced. I have been using one for about 5 years. I also am using there master cylinder on my Amazon. Kits are only available for the black bodied m/c so if that is a concern they are about $10US more.

[122344]

sory about the amazon link.https://www.ebay.com/itm/Wilwood-260-2636-Aluminum-Master-Cylinder-5-8-Bore-Girling-Style-Master-/113134987201