Lotus Elan

Brakes, servos, master cylinder bores.

PostPost by: berni29 » Sat Jan 14, 2006 8:49 pm

Hi Again

I was having a problem with brake fluid loss a while back. I changed the master cylinder (for one which had been rebuilt a couple of years back) because it was depositing drips of brake fluid into the footwell. Then I could not get a hard pedal, and the fluid is still going somewhere. Also there is fluid appearing in the pedal box under the master cylinders. Then one morning there is a pool of brake fluid under the drivers side rear wheel. Ok, so I change the rear calliper for one I have lying about. Bleed the brakes, no hard pedal, no real change. Then while trying to fix an earth problem I ended up pulling off the vacuum to the servo. The servo (although apparently working fine) is full of fluid, so off that comes to be replaced by a length of brake pipe. It looks like the clutch master cylinder is porous and dripping fluid into the top of the pedal box. There is no other way it can get there is there? Assuming the pipe union is not leaking, which it seems not to be.

I did not notice at the time but the brake master cylinder that I put on the car has a 5/8 bore. Has anyone here run a plus 2 with that bore and no servo? I do have another one marked "75" but that would give increased pedal pressure would it not? I looked back through the archive and some say that greenstuff pads have a higher friction coefficient than standard pads. I do have a set that I can put on the car if it will make a difference. I have not had a chance to do a test drive because it is not driveable at the moment while I have it apart trying to fix the windows (and other niggles).

As for the clutch master cylinder the one that I think is porous is a 5/8 unit. I have another 5/8 unit, and one that says .70 on it from my yellow plus 2. That always had a really hard switch like clutch. I guess that I will recondition the 5/8 unit. Were .70 cylinders ever used?

And I though that by buying a "rebuilt" car I was going to avoid all of this. Right!

Racing green +2s with green tints. See it at:

User avatar
Third Gear
Third Gear
Posts: 387
Joined: 10 Mar 2004
Location: Beckenham Kent

PostPost by: john.p.clegg » Sat Jan 14, 2006 10:12 pm

The figures i've got are
Brake master cylinder 0.7"
clutch master cylinder 0.6252 (5/8th inch)
clutch slave cylinder 0.875 (7/8th inch)

John :wink:
User avatar
Coveted Fifth Gear
Coveted Fifth Gear
Posts: 5691
Joined: 21 Sep 2003
Location: Manchester

PostPost by: patrics » Sun Jan 15, 2006 12:28 am

Hello Berni, If you are loosing fluid you have a leak. check all the joints/conections there are plenty in the diff area,.
It takes a lot for a caliper to leak and I wouldn't expect a m/cyl to become porous. So apart from the leaky servo your problems will be just (hopfully) leaky joints. Check the 3 way by the diff. wipe all the joint dry with paper and be happy that there is no leaks then put some pressure in to the system and recheck.
Best Regards
Fourth Gear
Fourth Gear
Posts: 542
Joined: 21 Sep 2003

PostPost by: john-c-elan+2 » Sun Jan 15, 2006 3:58 pm

Hi Bernie, My JPS has an 0.70" brake master cyl which was correct for the car. The clutch mas cyl is 5/8" which is correct for +2 and baby elans too.
The seal kit for +2 (0.70") brake master cyl is Girling SP2431. I may have a spare kit here somewhere if you need one. Rgds jon
Second Gear
Second Gear
Posts: 125
Joined: 22 Sep 2003

Total Online:

Users browsing this forum: No registered users and 15 guests