Braking Problem

[David Sleith]

Folks

Got crap brakes and not sure whats wrong.

The setup is a Mk2 master cylinder, ST205 fronts and Mk2 22V rears. The system has been bled a few times now and def no air in there now. Engine off and brake pedal pumped makes pedal go hard. Pedal depressed and engine started and the pedal depresses right to the bottom and continues to do so every time I depress the pedal with only a slight amount of pressure.

Traced the vacuum pipe all the way back to the engine and everything seems fine.

Not sure if I have a vacuum leak, faulty servo or a faulty master cylinder. There are no fluid leaks so I'm reckoning the brake system after the cylinder is ok.

Any help on testing the above would be most appreciated.

I have a spare servo and the original Mk1 master cylinder but thought I would ask first here before I start to rip it all to bits again.

The engine runs fine with a 800-900 rpm tickover when warm and revs freely so i'm thinking if i had a leak it would have a lumpy idle. Correct me if I'm wrong?

[David Sleith]

Just had a thought.

If the Mk2 master cylinder has a different plunger depth than the Mk1 then the operating rod from the Mk1 servo might need to be adjusted.

Not dug the haynes manual out but I think seen a bit about adjusting the rod length.

Anybody running a Mk2 master cylinder on a Mk1?

[Gary Symons]

Just had a thought.

Anybody running a Mk2 master cylinder on a Mk1?

Running the same setup on mine with no problems so far. Didnt modify anything to get it to fit.

Hope you get it sorted soon.

[msherry21]

Hi Mate, I think Paul is putting one on mine, can't remember if we had sorted that. So he's probably the man to see amongst others who know far more then me!

[adamh]

does sound like a cylinder problem dave, couldnt see the calipers bleeding bieng a problem.

[David Sleith]

If there were a problem with the master cylinder seal then would you not expect a run of fluid down the servo casing where it meets the master cylinder.

What about the small white valve about a foot away from the servo which I assume is a one way valve. Would this cause the above problem?

My brain is telling me it must be something that has been changed prior to the mods as the brakes worked fine beforehand. This would rule out the servo and that small white valve unless the fact its been standing has caused something to go.

[OlberJ]

Exact same thing happened when i fitted the ST165's at the weekend.

Was just air in the system though. Worked fine after a good bleed.

[David Sleith]

Thats what I'm thinking.

Think I'm gonna go buy a mityvac vacuum pump for brake bleeding

[GaryA]

I find using pressure to bleed is better than vacuum as you tend to pull air past the thread of the bleed nipple wich makes you think you still have air in it . If you have rubber flexi pipes you could clamp the hoses to see if it makes the brake pedal better , has it got new pads and discs ?

[OlberJ]

Aye, it'll stick halfway otherwise.