hinchcliffe

OK, so last night I was getting ready to install the MC and said to myself, self lets power bleed again but push the pads back to force the cylinders back into the caliper. Wooooooo, tons of bubbles. I then held them high and rolled while power bleeding a couple more and that's it.

Pedal is usable again, though still feels a bit squishy. I do have the new MC that can go in so i'll do that anyway. Maybe I'll try to force the fluid back upwards, stop it then replace and bleed again.

Schocki

Had the same problem after painting all four calipers on my GTS. The brake bleeder was not sufficient to solve the problem.

This is a two person job. You need to bleed it the "old school" way. One person pumps the break pedal a couple of times and builds up pressure, as soon as pressure has build up, hold the pressure with the brake pedal.
THEN. The second person opens the bleeder at one caliper quickly and you should try to force as much fluid through the bleeder as quickly as possible in one downward movement of the brake pedal more! When the brake pedal is at the floor, HOLD it there! Close the bleeder first BEFORE you release the brake pedal. this will prevent the induction of air into the system.
Repeat this procedure as often as necessary to remove all air in the system. Watch the fluid level in the reservoir....

Mrmerlin

bleeding sequence
with new MC fill the reservoir,
open the lines 1 turn to the MC watch for air bubbles to come out the lines.

No air,
then open the MC bleeder and wait till clear.

Then LF, RF, LR, RR.

Yes this is backwards from the traditional way ,
but its in the WSM

hinchcliffe

By "lines" you mean the two that go to the master? That way air bleeds from the master and doesn'thead to the lines/ABS.

supercedar

Thanks Dr Bob,
What you are saying is not detailed in the WSM where the "press pedal firmly" while pressure bleeder is installed, but you make perfect sense to me. It does say this will bleed the air out of M/C though.

Thomas
Thomas

dr bob

There's a bleed port on the front of the MC that helps some with the MC installed in the car, but it only bleeds the front section of the MC. Look at the way the MC is mounted and the locations of the hose connections, and see that they are low on the cylinder. So there will be a pocket of air that won't get pushed out through the lines to the calipers no matter what. MC bleed port takes care of the front section, rear does not have that option. The 'bench bleed' procedure pushes a lot of fluid out fast, and you can do it quickly while watching to see that you've actually cleared all the air out before you install the MC in the car. Remember that the MC has a two-piece piston assy inside, with check-valve disk built into the rear of the forward piston. Hydraulic pressure from the rear section pushes on the front piston, and there's usually only mechanical contact between them when the front brakes (driven by the rear piston...) don't hold pressure. The actual function of the MC is too often simplified in diagrams and descriptions, so you might not realize all the internal stuff that's in play. A little crud in that check-valve disk, for instance, is often fatal to correct function. Stupid stuff, and all the more reason to RELIGIOUSLY swap brake fluid annually.

granprixweiss928

There is no bleed valve on MC pre 1984.

mark kibort

sounds like you need a pressure bleeder and some two man technique. mine did exactly like you were saying. however, I think a lot of it was just the fact that you couldn't get all the air out with the traditional method, plus I had a bleeder screw broken, so had to bleed one caliper by using the crossover and turning the caliper upside down.

I know, it does feel like something is drastically wrong when you push the pedal, and it slowly goes to the floor and you have to punp it up to get a firm pedal again, which doesn't last. its air! mine is bullet now! but it took a while to get it right.

Five-8

I see what you did there Arlo

Cheers,