Master Brake Cylinder ?
 

OK we know the 90-91 have a dual cups.

The 92 & 93 a single cup and a hose going to the cup.

And the 94 & 95 have a single cup (but no hose? right)

The ? is what is the hose on the 92-93 for?

BTW no stock in at Rock Auto and all the other catalog houses on 92-96 MC's.

Even used are hard to find but I did have luck with

http://www.justcorvettes.com/

Re: Master Brake Cylinder ?
 

FWIW, I sent my master in for a rebuild, to Cardone (via RockAuto). Pretty quick turnaround, and no complaints since.

Re: Master Brake Cylinder ?
 

Yes PETE suggested I do this with mine as well once I install the used one from Just Corvettes. The Cardone rebuild via Rock does seem to be the best deal. This way I will have a good to go one in stock should my used one go down. Maybe I will luck out and the used one will last a good while. But just in case I think I will do the Cardone rebuild so I have a spare.

This way if any of the FAST gang get in the same pinch I am in now I can offer to help out and let them install my spare and return their Cardone Rebuilt via Rock to me and not have any down time.:cheers:

http://i126.photobucket.com/albums/p...1mcforzr-1.jpg

This is why I was wondering about the hose on the 92-93 and why no hose on the 94-96.

It is strange that the used part shops point this out but others do not - they lump them all as 92-96???

To HOSE or Not to HOSE that is the ? :dancing

http://i126.photobucket.com/albums/p...-WITH-HOSE.jpg

http://i126.photobucket.com/albums/p...C92-96HOLE.jpg

http://i126.photobucket.com/albums/p...6mcforzr-1.jpg

WHAT IS THE BLACK PART FOR?
AUTO BREATHER OF SOME SORT?

Re: Master Brake Cylinder ?
 

I'm curious. What is the failure on these that need to be rebuilt?
What is the symptom of the failure?

Re: Master Brake Cylinder ?
 

Spongy brakes - even after a bleed down and a new tight pedal - 15 days later (next time out) back to the spongy blues.

The MC is sucking air in upon each stroke.

Common known failure with all C4 MC's.

Re: Master Brake Cylinder ?
 

Agreed. I couldn't get a hard brake pedal no matter how much bleeding I did.

Re: Master Brake Cylinder ?
 

Brake Hose May Cause Low Pedal

How to diagnose a sinking, low or spongy brake pedal.

1. Begin by isolating the master cylinder. Remove the lines from the
master cylinder and insert blocking plugs into the ports. Press on
the brake pedal. If the pedal is firm and hard, the master cylinder
is good. If the pedal still drops, either air is in the unit or it is
bypassing internally. Bleed the unit or replace as necessary.
Reconnect and bleed the system.

2. With a properly bled master cylinder test the brake hoses. Using
a proper tool, carefully pinch off all the rubber brake hoses as
close to the master cylinder as possible. Release one brake hose
at a time. Press the brake pedal. If the brake pedal is firm and
hard, move to the next circuit. Repeat until the circuit containing
the defective component is located (the brake pedal will be soft
or sinking). Replace defective components as necessary.

http://i126.photobucket.com/albums/p...adlinetest.jpg

3. Flush the system thoroughly with fresh brake fluid from a sealed
container according to the manufacturer’s service procedures.

Re: Master Brake Cylinder ?
 

The GM service M/C does/did '92 - '96MY BUT to use it on '94MY and earlier you needed to transfer the reservoir or buy new and reuse the level sensor or buy new. The hole you indicate as for hose is actually the level sensor port. That is NOT an open port it is a "pass-through" for the level sensor. That image might likely do '92 - '96MY.

The only oddity here is that in '95MY base car MC changed BUT the ZR-1 used the reservoir and level indicator that was used for the previous years '92 - '94MY. If you check a '95 - '96MY base car you'll see no level sensor.

Re: Master Brake Cylinder ?
 

It maybe a common failure but I've never experienced it in 15yrs of ownership and 92k miles. Maybe it's in how I flush and bleed them.
Don't know. I learned on my 72 vett not to just push a lot of fluid through the system. And to flush every few years even if the pads are ok. I'll be doing that service again this fall. We'll see if my luck holds.

Re: Master Brake Cylinder ?
 

I know a guy who's addicted to brake fluid. He says he can stop any time.

Re: Master Brake Cylinder ?
 

WVZR-1 You caught me in edit mode and my old photos posted before my edits did in your quote capture. LOL

Re: Master Brake Cylinder ?
 

I think you are lucky SF

I bet olde Murphy will visit your MC soon.

Then again perhaps the constant attention is making a difference for you.

My Z is a only @ 64K now and the MC has been bad since 62K.

Re: Master Brake Cylinder ?
 

I hope I didn't jinx myself. Driving home from work yesterday, my brake pedal was quite soft, with a long travel. Got home, and the forward reservoir was nearly dry (scary!). Today, I inspected the entire system, I can find no evidence of a leak (other than some bubbling caliper powdercoating near the RH front caliper bleeder screw.

Here's where it gets weird.

I bled all 4 calipers -- all the while checking for leaks (none). However, the LH front caliper really didn't give me a good solid fluid stream like the other calipers did, so I'm kind of scratching my head about that one. I did use a vacuum bleeding system, BTW.

So, I tightened the bleeder screws, topped off the fluid, and the brake pedal is now firm as it used to be. I don't get it at all. No signs of leaks anywhere. Perhaps master cylinder leaking into brake booster, only from the front portion of the cylinder? I don't know if that is even possible...

Re: Master Brake Cylinder ?
 

Had a similar experience using vacuum on an Explorer.
Used the peddle to bleed them and the softness went away.

Re: Master Brake Cylinder ?
 

Wifey's 91 base car is leaking fluid from the front to the rear reservoir, so
that might be your problem. I just transfer fluid back where it belongs every so often.

Re: Master Brake Cylinder ?
 

IF the master is sucking air in, then there is no venting between the booster and the master. Perhaps someone put sealer in between? They must vent.
I do HYDROBOOST conversions, and can build for the C-4's. With a HYDROBOOST booster, I run a c0ommon 1" master, even one from a C-5 can be used. Gives outstanding braking performance, AND a firmer pedal

Re: Master Brake Cylinder ?
 

Got my attention.
Mind starting another post about this hydroboosting etc. and tell us a bit more ?

TIA :handshak:

Re: Master Brake Cylinder ? Hydroboost solution
 

I have rebuilt many of the C-4 masters, and thousands of the C-2,C3 masters.
In looking at the vacuum boosters on the ZR-1's, I notice how ugly that computer wiring harness is, and how ugly the computer looks sitting where it is.
With a HYDROBOOST brake booster, which runs off of the p/s pump, the wiring harness can be run under the booster. The battery can be relocated to the rear compartment, and the computer put in it's place.
The stopping power of a Hydroboost is unbelievable! It can deliver up to 2000psi to the calipers at idle pump speed.
We can use a more conventional master cyl, say of of the C-5, which is 1 inch. This gives you a much firmer pedal, and the stopping power will stop the car faster than you can accelerate.
Many pluses start to stack up with this system.

Re: Master Brake Cylinder ?
 

These are the before photos of the wiring harness and computer wrapped over the vacuum booster. With the Hydroboost, and the battery moved back to the compartment, the harness can be rerouted to under the Hydroboost and the computer relocated to where the battery was. . We use a 1 inch master for a better pedal feel.
There are just so many advantages here.

Re: Master Brake Cylinder to Hydroboost with 1" master
 

My dual dia booster was getting tired finally at 260,000 miles, and so was the Master. I rebuilt it once 15 years ago. In looking at it, I decided that the placement of the computer and wiring was unsightly. I elected to move the battery to the rear compartment, and install the Hydroboost. This eliminates the Australian Booster, and 7/8" marginal master cyl. This also works well, if you want to install C5 calipers, which came from the factory with a 1" master. The Australian booster has an odd bolt pattern where the master bolts on. Hydroboost uses std GM 3.375" spread. Stopping power is phenomenal. Stretches the seat belts.

Re: Master Brake Cylinder ?
 

Bob, you should speak with Robert DeMarco about your system. The right marketing may get you some business. Robert handles our Registry Store and all promotions and discounted items.

Robert DeMarco's screen name here is cvette98pacecar
Brett Henderson

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