Hi
Having trouble with a rear master cylinder on a lemans mk2
ive fitted a new cylinder repair kit and im not getting much pressure from it .
in side the reservoir their are two holes , one is very small but seem clear , is this normal or are both the holes supposed to be the same size .
any help appreciated
One is the fluid feed to the master cylinder, the other is the air bleed, usually comes back from between the master cylinder piston seals (and also shoots a little squirt of fluid back at low fluid levels)
1 Like
I have just refurbished the rear master on my Le Mans (mk1) but think the pressure is not up to much, but have not yet done a road test.
Inspecting the barrel of the cylinder I can observe what looks like a wear depression to the upper area where the two holes reside, and I suspect this is causing a loss of pressure.
Secondhand Mk 1 / 2 versions are available, but my concern is these will be no better. But a new version as used on later models is available and because this is the brakes I am of the view stopping properly is more important than aesthetics, so I will likely take the non-purist approach to resolving this one.
Available from Gutsibits
1 Like
A replacement master cylinder is obviously an option but if you would like to retain originality, and original parts no longer available (don’t think Brembo round reservoir PS12’s or the rears with the integral cast reservoirs are), it’s possible to get them sleeved if it’s only the bore that is corroded/pitted from standing in a barn or similar. The cylinder is bored out and a stainless sleeve pressed in and bonded in position, the two small holes to the reservoir are drilled and then the sleeve reamed to size, and you can then fit the new piston, seals, spring, etc that come with the kit. One of the companies that do this is Past Parts in Bury St Edmunds, around £50 plus VAT + shipping, and obviously + cost of repair kit.
I think their website has a video of the process which explains things quite well.
I didn’t know this was a ‘thing’, but apparently quite a common on classic cars where OEM parts are no longer available. As the sleeve is stainless then it’s not going to corrode if left standing with water in the brake fluid.
1 Like
The system usually needs pumping for a few minutes to buid up pressure in the system after disturbing things. I think it seats the caliper pistons closer into the discs.
Others swear by tying the pedal down overnight.