grandpa ralph

After pulling the MC this is my booster and pushrod. There are about 15 threads showing.





From I another post I read, I put a dab of grease on the end and put the MC back on. It was making very solid contact and forced the grease off the end. I turned the nut in 2 full turns and put the MC back on and tested. Still have the low pedal.

For those who have done it, where do you put the feeler gauge to measure clearance?

Thanks.

brainfade

Hey Gramps,

The booster push rod should have near zero clearance to the M/C piston when installed. The best way to measure this is with a depth mic and some jigs, which of course no one but the manufacturer has. A quick and dirty method that will get you close is to use a feeler gauge between the mounting face of the booster and the M/C. Lengthen the booster output rod until a .005 feeler gauge will just slip in there while holding the M/C against the booster, then shorten the rod 1/2 turn. This will put you in the ball park.

What you don't want is the booster rod to hold the M/C piston part way down the bore as the fluid won't be able to return to the M/C reservior and the brakes will drag and get hot.

Also, relative to your other thread, you should be able to get 1800 psi + out of the M/C with full boost and 150 lbs on the pedal. 450 psi is quite low and would make me look at the M/C. It may be bypassing internally.

grandpa ralph

Thanks Brainfade,

I got a new master today.

I'm still not getting where the feeler goes. The booster and MC have interlocking parts, so when they are pushed together the pushrod is completely covered.

NotEnufGarage

I think you want to measure between the booster and the flange face on the M/C such that it bottoms out on the feeler gauge right before you feel some resistance from the pushrod pushing the M/C.

grandpa ralph

Ok, feeling for the resistance from the MC is the part I was missing.

brainfade

Yup, Garage has it spot on. Where you have the gauge in the photo is fine. You'll have to use your calibrated eyeball to see if the M/C is square to the booster, but that's easy. Just push the M/C up to the booster with the gauge in there and feel for resistance when you pull the gauge out, just like adjusting a valve. Lengthen the booster push rod until the gauge slides out easy, then the 1/2 turn in. You don't want too much push on the M/C, you don't want to push the piston in. Just push it up until it stops without putting a lot of force on it.

Edit: Just happened to think: If the M/C has an O-ring that seals to the booster you'll need to pull that while doing the set up. Can't remember if these have one or not.