7 replies to this topic

[MiniLandy]

Looking for a guide on how to rebuild my brake master cylinder from a 1990 car, green tag type. Rebuilding them seems to be discussed quite a lot on here but couldn't find a guide. 

Edited by MiniLandy, 03 July 2013 - 09:10 PM.

[Webstercon]

I got an instruction leaflet with my master cylinder rebuild kit, pretty simple and goes through it step by step, mine is however the yellow tag type. Have you looked through haynes?

[MiniLandy]

Had a look through the Haynes manual, but although the manual I have says it includes all up to 91, it doesn't include my type of master. 

 

Think I'm just going to invest in a new master cylinder. 

[KernowCooper]

The strip and rebuild will be the same its bore sizes which vary, the method will be near as dammit identicle

Edited by KernowCooper, 03 July 2013 - 10:32 PM.

[Webstercon]

If you can get a rebuild kit I'd definitely recommend doing that rather than shelling out for a new master cylinder, it really is pretty easy and much cheaper

[Ethel]

Everything goes in and comes out the same hole, so just do it carefully, to release the spring pressure without firing bits all over the shop. There'll be a little retainer pin for the forward piston accessible by removing the reservoir and the rubber bungs it sits in.

 

A generic diagram, note how the rubber seals (black) are cupped so the fluid pressure forces them  against the cylinder wall, a bit like a squeegy blade. The cup on the back of the front piston faces backwards as it uses the pressure in the rear circuit to push it for the front circuit. Pay particular attention to the order of the parts between the springs and the cup seals, they act as a return valve - sounds far more complicated than it is, as you'll see.

 

Also try to squint along the cylinder bore to make sure there's no pitting or ridges. Most likely it is just the soft rubber bits that have split.

[tiger99]

You should dismantle and thoroughly inspect the bores before deciding to rebuild. The slightest scoring or corrosion in the bore means that it is scrap, so no point in buying the rebuild kit until it is confirmed to be usable. I have found that about half are ok, half are scrap, averaged over all cars that I have owned, not just Minis. Largely pot luck, plus some are better protected than others from the ingress of dirt and water.

[MiniLandy]

After a bit more reading, and finding out that the circlip had snapped so I couldn't rebuild it anyway, I've ordered a new one.

 

Cheers anyway chaps.