633 E24 Dual Boosters

[richard.pykett 36]

Hi All, long time no post...

Not much progress on the Group 5, but have been doing a refurb on the old 633 along with some stainless headers etc...

I had the dual remote boosters refurbed by Sterling Brake and Clutch, which I gather involved the usual sleeving process and the manufacture of new pistons.

Unfortunately we now seem to have a brake binding issue with the engine running.

If you pump the brakes with the engine running, all 4 wheels are lightly locked. As soon as you kill the engine and thus the vacuum, the wheels are free to rotate normally.

I've had the car into them for diagnosis and then dropped the boosters back in for checking. They reckon that they deepened the pushrod holes in the back of the new pistons to give more clearance, but on reinstalling them today and bleeding up the brakes again, the same problem exists.

Because there was some considerable delay in me reinstalling the rebuilt boosters, obviously the old pistons have been thrown out, so I have no way of cross checking their dimensions.

Does anybody have a pair of boosters that I could buy or borrow so that I can pull mine apart and go over the dimensions please? 

Clearly something is not right with the new bits they have made. Mine is the early E12 based car.

Thanks.

 

Richard

 

 

[hotwire 352]

Surely the best bet is to go back to them?

[richard.pykett 36]

Hi Grant, well it seems that they f**ked it up the first time and haven't been able to fix it the second time, with no doubt the original bits long been thrown out... It costs me a day each time to take the boosters out, take them over there and then reinstall and bleed the bastard of a system. What pisses me off most is that I could have machined up the pistons myself from the originals, but trusted them as they have been around forever. Way forward from here is to get hold of an original to measure, or bite the bullet and get two rebuilt and tested units from the UK.