When brake bleeding goes bad....I need some help

[PorscheGuy79]

After hours of trying to bleed the system on my SC, I have finally called it quits and retired to my room. It seems they just wont stay bled. Okay here is what is going on. I am bleeding them with the use of the pedal and ive got it where I think the master cylinder is bled. Here is what it looks like:

1. Dad pumps the pedal a few times and then holds it down.

2. I open the bleeder valve and the fuild shoots out.

3. After each of the corners the pedal gets firmer, the level of the master lowers just a bit.

4. On the last corner, the front drivers side (closest to the master) I do that same procedure as above and the master goes down a bit but the pedal gets loose.

5. When no one is touching anything the level of fluid in the master slowly creeps up.

6. If I pump the pedal a bit it gets firmer and then after a few seconds looses its firmness.

Please tell me whats going wrong!



Thanks in advance.

[RANDY P]

you rebuilt the calipers right?

If the pistons are totally seated in the bores then there's a slight gap that's created when you're off the brakes. Remove the pads one caliper at a time, have someone slightly apply braking pressure and let the pistons push out slightly (insert something to stop them like a paint mixing stick or a piece of wood. Push the pistons back just far enough so you have to wedge the pads back in, like literally tap them into place it's so tight. Rebleed and try it again. This always trips people up.

Good luck

[einreb]

Originally posted by RANDY P
you rebuilt the calipers right?

If the pistons are totally seated in the bores then there's a slight gap that's created when you're off the brakes.

thats a good guess! i had other less viable guesses on your gruppe b post.

-Bernie

[Jim Sims]

I will speculate the MC is now bad. Given the age of the car the "pump the pedal" method may have taken the seals into normally unused and rusty sections of the MC bores thereby damaging them. Jim

[PorscheGuy79]

Originally posted by Jim Sims
I will speculate the MC is now bad. Given the age of the car the "pump the pedal" method may have taken the seals into normally unused and rusty sections of the MC bores thereby damaging them. Jim

Bugger, I was thinking that might be the case...

[RoninLB]

Originally posted by RANDY P
Push the pistons back just far enough so you have to wedge the pads back in, like literally tap them into place it's so tight.

ditto.. afaik the piston seal is shaped so it'll pull the piston back initally unless it's over-stroked to begin with.

[MotoSook]

Jim might be right Matt (hence my warning earlier), but the fact that you can build pressure and hold it may also indicate that Randy and Ron might be right. I wouldn't write-off the MC just yet.

"5. When no one is touching anything the level of fluid in the master [reservoir?] slowly creeps up." .............Ask yourself what's causing this?

[PorscheGuy79]

Souk give some guidence, what would be your next move?

Originally posted by Souk

"5. When no one is touching anything the level of fluid in the master [reservoir?] slowly creeps up." .............Ask yourself what's causing this?

Yeah, I think its the fluid pushing back through busted seals on my master cylinder.