an6drew

I recently replaced pads & discs on my '82SC, flushed & bled the system. Unfortunately I now have a pedal that is super-spongy. When dead cold the pedal hits the mechanical stop before getting much stopping power at all. Things get better when warmed up, but it still feels real spongy.

Hers some more info:
-had a second attempt at bleeding a few days later & no air bubbles showed up.
-pumping the pedal doesn't seem to improve things much, if at all.
-I've driven maybe 300 miles since doing the work. If it was an issue with the pads beig seated too far from the rotors it seems they would have worked their way in by now?
-I think the vacuum assist works. I f i depress the pedal w/ the car off it sinks further to the floor when I start it up.
-seems to be no brake fluid loss

My (uneducated) suspicion is the master cylinder is gone. Thing is everything seemed to work fine before, but I wonder if bleeding the system (with helper depressing pedal) damaged a seal or something. Does this sound right- I don't wanty to throw money at new parts needlessley.

thanks,
Andrew

geo.aigel

Your suspicion is likely correct. You need a new master cylinder!

What happens in assistant bleeding by pumping the pedal? The cylinder gets pushed into the bore deeper than it ever is during normal operation. You are putting the pedal to the floor! The bore and seals can suffer from by debris and wear patterns that get pushed into 'virgin' areas of the bore.

It is too late now, but for future reference, get a pressure bleeder like the one from motive products: www.motiveproducts.com which will avoid that you have to pump with the MC. Unless you have some serious bubbles hidden (after line replacements etc.) the power bleeder will do the job perfectly. That's all that is used in shops these days and all that I use to service our 4 vehicle's brake systems!

Good Luck,

George

bell

before you buy a new master cylinder........

did you bleed in this order? right rear.....left rear..right front....left front....
if you don't do this sequence you'll never get all the air out.

also make sure your bleeder nipples are at the top if you had the calipers off.......the fronts can be easily mixed up and will bolt right on......

and the motive power bleeded is a blessing........i'll never bleed brakes again without using it

Trust me

Also, Did you let the fluid level get too low when bleeding the brakes? If you do not keep the fluid filled, it just sucks more air in.

Bill Gregory

Andrew,

Having a helper push the brake pedal to the floor to bleed brakes is a guaranteed way to get set up for a new master cylinder. What happens is that over time, the seals move in a very narrow range in the master cylinder. Outside of that range, corrosion builds up over time. When you have someone push the pedal to the floor to bleed brakes, especially on a high mileage car, you rip the internal seals. That's why you either pressure bleed or vacuum bleed the brakes. With the engine running, push hard on the brakes and keep the pressure up. If the pedal slowly goes to the floor, your diagnosis is correct.

an6drew

Thanks for the feedback. When bleeding i did go around the car in the correct sequence, & kept fluid in the reservoir. The mushiness isn't getting better w/ driving & the pedal continues to sink until it hits a mechanical stop (at least thats what i think is happening- the pedal isn't supposed to actually go all the way to the floor is it???).

I'm ordering a new MC, & then w/ hopefully be back in action.

Andrew