Lotus Elan

Tandem brake master cylinder

PostPost by: Mazzini » Sun Jun 21, 2020 9:17 am

mariodschy wrote:
pharriso wrote:
crypto wrote:
I browsed thru the shops of the well know suppliers but could not find a suitable tandem master cylinder.
As far I know they where only equipped on the federal versions ? Do they have two servos then or none at all ?


Thanks Peter


No servos, there isn't enough room.


Can confirm, originally there were tandem master cylinder but no servos on Fed Sprints


I think Federal +2's had two servos, not sure about Federal Sprints. but I have a friend with a very original LHD European spec Sprint 5 and that doesn't have dual servos.

Were European spec and Federal spec different? I suspect they were.
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PostPost by: Mazzini » Sun Jun 21, 2020 9:23 am

nmauduit wrote:
Mazzini wrote:I guess the M/C is to blame. I had it apart before I fitted it, but put it back together the same way. The only thing I did was remove the needle shaped bolt that stops the piston from going back past that point.

Any ideas where I am going wrong?


I understand you don't have a brake booster.

I'm not sure I get this : are you saying that you just removed the bolt it then put it back (one usually needs to push on the rod to reinstall the stop nut back because of the internal spring), or did you remove the piston then reinstall everything? There is a small hole that interconnects the fluid tank with the MC pressure area, and the motion of the piston opens or closes that opening when it moves (normally open at rest position which also enables fluid to get back into the braking circuit, then when one presses the pedal the seals passes over the small hole and effectively seals the braking circuit from the spare fluid circuit). If the piston resting position is not adequate it is possible to get pressure build up inthe circuit (it is also possibe to get similar self locking behavior if some debris are back clogging the small hole, e.g. brake seal edge that would have been cut off when installing the piston dry against a sharp internal edge).


Thank you for your response.

You're right, I don't have a servo.

A poster recommended that I remove the bolt, which I did, I replaced it with a blanking plug/bolt just to make the seal. I guess this could be the problem?

I changed the brake fluid when I bled the system, but it looks like there is come sort of contaminate in it, I'll drain it and clean the M/C out before flushing it though.
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PostPost by: Galwaylotus » Sun Jun 21, 2020 10:56 am

Mazzini wrote:I made and fitted new brake pipes, plumbed in the new master cylinder and went for a drive. I have +2 discs and calipers on my Sprint. The brakes felt a bit wooden, but then they got better. After twenty miles the brakes started binding. I stopped then car and jacked up each corner, I could rotate the wheels but there was some resistance. I let the car cool down. I managed to tap the pads back and drove home with brakes that functioned perfectly (good pedal).

Later I took the car on a short drive. The brakes functioned well, till the last mile or two, then they started to bind again.

The front and rear calipers have new SS pistons and worked fine before the M/C swap.

I guess the M/C is to blame. I had it apart before I fitted it, but put it back together the same way. The only thing I did was remove the needle shaped bolt that stops the piston from going back past that point.

Any ideas where I am going wrong?

I had a problem with brakes binding when I installed new pads. As I discovered, the pad backing plate was binding in the caliper. It was just a little too tight and wouldn't release properly. Make sure that isn't your issue rather than a m/c problem.
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