wlt911

Greetings all. I am new here and am hoping I can get some answers. I recently did a total brake job on my 82 911SC. I did it all. The vacuum booster was leak-free so it was not addressed. I replaced the master cylinder (all parts were name-brand items from Bosch, Wagner, Raybestos, Centric, etc.). I replaced the rubber hydraulic hoses at each wheel. Brand new calipers. Brand new rotors. New hardware. And, of course, new pads (Centric #13037002). Basically, a brand-new braking system.

Pedal travel is spot on. However it feels like the pads never “grip” the rotors. It takes a lot of extra effort to stop in the last three percent of pedal travel. I have done some “breaking in” with hard controlled stops at speed. No improvement whatsoever.

The system has been power bled twice.

I can feel when pads make contact with the rotors, but then it feels like the pads are just skimming over the rotor. It takes a strong foot to come to a quick stop. It’s hard to get that “biting feel”.

I am looking for ideas/suggestions. I am using premium daily-driver Centric pads. I would use a more aggressive pads if that would help. New rotors are not that expensive.





Thanks

theiceman

how long have you been driving it since the brake job ? did you rebuild the caliper with new seals ? i would suggest driving it for a few days and see if things improve before doing anything. It takes a little while if you used new caliper seals to bed in and not pull the piston back.
Just a suggestion.

wlt911

I used all brand new parts. It's been a couple hundred miles ago.

theiceman

oh that should all be fine by now .. you can try slipping the old pads back in if you have any meat left on them. would tell you if its a pad material issue.

wareaglescott

You said you pressure bleed it. I have one of those also but find at the end the ole pump at the brake 3 times and then hold the pedal and manually open the caliper gets the last little bit of air out a little better. Maybe try that old school technique and see if it helps.

wlt911

The second bleeding was done at a very competent shop. His power-bleeding apparatus was one step above my Motive bleeder system.
I'm in process in doing the "hard stops from 60 mph" thing. Hard to do inconspicuously here in the city.
I would still like to know more about that second Centric master cylinder part number on the Rock Auto site. I'm thinking a possibility that it may have an internal dimension (bore size, piston size, stroke, etc.) that uses the same valve body so nothing would be obvious save for the different part number.

Batman 357

New rotors will need to get some pad transfer on them to have a good bite. I'd try a few 60 to 5's. Do enough to feal a real difference and get some brake odor. Then add a long easy cool off drive. If no improvement I might try differnet pads.

wlt911

Literally every part was replaced. Vacuum booster system thoroughly checked out.
When sitting in car while idling (zero mph) I can press brake pedal and feel that the pedal it comes to a very hard stop. The rod is definitely hitting something and it is definitely not the pads/rotors as the distinctive "thud" is coming from the MC area under the dash. I am able to both hear and feel the resultant "thud" through the brake pedal. It definitely is not a any pocket of air in the system (power bled twice by competent tech)..
I was a process controls tech at a few very large generating stations for over thirty years and have oodles of experience setting up hundreds of valves of all types. The first step in setting up most valves is adjusting the stem to get proper stroke length. I can see there is a nut and turnbuckle at the pedal end of the MC rod for adjusting the cylinder rod length. I think the rod is too long and needs to be shortened. I had MC replaced at a shop so who knows where they have it adjusted to. I'll try two turns of the turnbuckle which should shorten the total rod length. This should prevent the end of the rod from hitting the end of the cylinder bore which is what I think is happening.

I've had car for twenty years. I've done pads more than once with ZERO issues. I had a shop replace the master cylinder due to my lack of familiarity. With brand new calipers, pads, rotors and rubber brake lines, i can't see any other possibilities.