Did you bench bleed the master cylinder before installing?

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Question Authority before it Questions you.

Sinking pedal suggests a worn master cyl to me.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

"Sinking pedal suggests a worn master cyl to me."

Re-read the post. This is his SECOND brand NEW master cylinder.....

BTW - That car is friggin' GORGEOUS!

-tp

Thanks for the comments on the car. I am actually a bmw man but the car was recently gifted to me from my grandfathers estate. So its been in the family for a long time and I thought it was well worth presevering. The old boy picked it up from the factory in Stutgard as a tourist delivery, drove it through europe and then put it back on a slow boat to New Zealand.

The masters could be bad even though new.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

First you have to check if all pistons are free and the brake pats are not worn.

Air may be trapped is the system.
One way to get rid of it is start the engine, apply pressure on the pedal (as much as possible) and keep the pedal depressed over night.

If that does not work you can try to bleed from the bleeders with a large syringe (be very careful not to overfill the reservoir).

Rob

I know thats one reason, but as I have been through two new factory cylinders it would point towards it not being in this case. Unless I am destorying the cylinders in the bleeding process I dont think its the culpret.

There are multiple scenarios that could theoretically cause this it just a matter of comming up with procedures to eliminate each on in turn.

I think my next move will be to 'blank' of the master cylinder from everything other than the master cylinder to try and pin it down the one of the two units and exlude the rest of the braking system. Does anyone know a good method of blocking the holes in the master where the brake pipe flanges normally go. I dont just want to screw a bolt down in the event I damage the flange. Once again any advice on this much appreicated

I sent the brand new cylinder out to a pro who I assume bench checked it. I installed it dry but bleed the cylinder in place with all the brake pipes disconnected. I quickly got a cylinder of fluid and good pressure and then reconnected the system. I bleed more than two litres through the lines.