Brake Master cylinder - rebuild or buy rebuilt?

[VetteMed]

I've now bled my brake system 3 times - including bleeding the master cylinder prior to bleeding the 4 wheels, as per the FSM. The pedal sinks right to the floor when pressure is applied. I figure the Master is leaking internally, though I've disassembled it and can find no obvious defective seals. I see rebuilt units for $150-$200, and am tempted to go this route rather than rebuild my original unit. Keep in mind this is the original '91 master cylinder, with 188k miles on it. Comments?

[VetteMed]

Update: ordered a Dorman from RockAuto, for around $160. Will update when I receive part.

[Corvette95]

Who can rebuild them? I dont think ZFDoc does anymore

[VetteMed]

Update: Dorman part is not in stock, 2-3 week backorder. Next available part was $200+, so I am going to try my luck with the Cardone rebuilding service. I have to send in my master and they rebuild it. Not much to lose for $60, comes with 1 yr warranty.

[GOLDCYLON]

Who can rebuild them? I dont think ZFDoc does anymore


Nope just the clutch cylinders and salves cylinders from time to time

[GOLDCYLON]

I've now bled my brake system 3 times - including bleeding the master cylinder prior to bleeding the 4 wheels, as per the FSM. The pedal sinks right to the floor when pressure is applied. I figure the Master is leaking internally, though I've disassembled it and can find no obvious defective seals. I see rebuilt units for $150-$200, and am tempted to go this route rather than rebuild my original unit. Keep in mind this is the original '91 master cylinder, with 188k miles on it. Comments?

looked at the brake booster as well ?

[todesengel]

Who can rebuild them? I dont think ZFDoc does anymore

I would think anyone who offers a rebuild service for any master cylinder. Is there anything overly special about the master, well besides being on a zr-1 and being attached to a zf :dunno:

[VetteMed]

looked at the brake booster as well ?

Hmm, no.. what's the symptoms and how do I test it? Is it in the FSM?

[xlr8nflorida]

Hmm, no.. what's the symptoms and how do I test it? Is it in the FSM?

I believe I may have a new ac delco master cylinder and new brake booster.

Let me know if i can help.

I'd probably rebuild it though, when I bought those parts they were pricey. Hundreds each not $60.

How can you go wrong with a 1 year warranty?

[GOLDCYLON]

Hmm, no.. what's the symptoms and how do I test it? Is it in the FSM?

Pedal to the floor as well. Usually you hear a vaccum type hiss at the booster while pushing down at the pedal unless the diaphram has completely blow out that is. With that many miles I would replace the master just for GP

[tomtom72]

I was just thinking about this issue. The pedal was okay before you took the Brake master apart, right?

When you tore it down did you go into the area where the brake bias spring is housed? Did you install a DRM bias spring?

Not trying to be a wise guy. If the bias spring isn't put back correctly, not just in it's bore also assembled right, you could have an internal bleed off of pressure....I think..if I remember the instructions that came with the DRM spring.

Also, check to make sure that the brake pressure warning switch is installed back correctly if you took it out. It has a pin that needs a specific location in the main piston (?) assembly...not sure if I remember right, it could be the bias assembly :o I forget it was a long time ago....but if the swich's pin doesn't go back where it belongs I think that bleeds internal pressure also.

:redface: I wish I could be more specific, I'm sorry it was like almost 5 yrs ago when I rebuilt my master & installed the DRM bias spring. It wasn't an easy rebuild as the only other vette master I did was on my 72 non-P/B and it was simple vs the 90 master cylinder.

:cheers:
Tom

[VetteMed]

Tom, I did in fact install the DRM spring, and unfortunately I shipped off the master for rebuild today. Maybe unnecessary, but I guess I can justify it with close to 190k miles on it... It is possible that I did not reinstall the warning switch properly, though now I can't be sure.