Write-Up: Brake Master Cylinder - Install & Bench Bleed

click to see write-up:
http://rivperformance.editboard.com/brakes-suspension-f6/master-cylinderbig-job-or-not-so-big-t6748-45.htm

Here is the situation. After sitting for a long while, the brakes have pretty much gone on my Riv. I am told that this happens when they sit for a long while. Well I finally got the car running again and it is time to work on the brakes.

Anyway the rotors/pads are good. I had the system professionally flushed, because I thought they could do a better job then me. So I have to assume that either the Booster or Master Cylinder have failed.

Has anyone else had to replace these parts? How do I know which one is bad?

How does the brake pedal act?
If it is rock hard, and the car will stop with LOTS of pressure on the pedal, then it is the booster.
If it fades, will pump-up and then goes to the floor, it is the master cyl.
These are diagnostics in the simplest terms but could determine which it is?

99Rivman wrote:

How does the brake pedal act?
If it fades, will pump-up and then goes to the floor, it is the master cyl.
These are diagnostics in the simplest terms but could determine which it is?

Thanks for the info..
Yeah it is just soft and goes right to the floor. I could pump it and get just the minimal amount of resistance before it is on the floor again.

Obviously it is pretty unsafe. I was ideling around the block and then suddenly the "brake" warning light came on and started beeping. It normally does when you are in drive with the parking break on. At first I was thinking, oh great first the brakes and now the E-brake is forked up. Now I am rethinking that. Is our ABS system smart enough to know when you pretty much have no brakes? I hope so, because I really dont feel like un-sticking an e-brake cable.

It sounds like a master leaking internally, the piston cups will go bad and instead of pushing fluid into the lines it will bleed back past the pistons into the master. The ABS can be a whole different problem but it sounds to me like a bad master cylinder.
The e-brake on these is a pain too, if that part of the rear caliper get screwed up, it is mechanical, they are a real pain to rebuild. I checked on rear calipers for my '92 a while back, same basic system, and the caliper was about $70 and the rebuild kit was almost non-existent.

it's the master cylinder. Not hard to replace, but you'll need to re-bleed the system again when you're done. frown

E-brake is unrelated, separate issue.

_________________
"An intercooled, supercharged, 280 HP Buick Riviera with neck-snapping acceleration and precise handling that proves GM can make something really interesting and competent, if only they would build more than one at a time."
- John R. White, Boston Globe

"I think that in any racing engine, the nearer you are to disintegrating, in general the better its performance will be."
- Keith Duckworth, Cosworth Engineering

'98 SC Riviera • 238k miles • 298 HP/370 LB-FT • 0-60: 5.79s • ET: 13.97 @ 99.28 • 4087 lb • 20.5 avg MPG

3.4" pulley • AL104 plugs • 180º t-stat • FWI w/K&N • 1.9:1 rockers • OR pushrods • LS6 valve springs • SLP headers • ZZP fuel rails
KYB GR2 struts • MaxAir shocks • Addco F/Rsway bars • ES links/bushings • GM strut brace • Enkei 18" EV5s • Dunlop DZ101 tires
F-body calipers • EBC bluestuff/Hawk HP plus • SS lines • slotted discs • ATE superblue fluid • DHP tuned • Aeroforce • Hidden Hitch

Make sure you bench bleed the master before installing, it makes for a quicker job. cheers

they usually come pre bled dont they?? i just did rear hard lines on mine..bleeding was a breeze,changed out the old fluid too...the old stuff i bled out looked like coffee..lol brakes work twice as good now..except for the fact that i couldnt bleed the pass fron caliper cuz the bleeder broke off inside the caliper....yayyy i get to buy a new caliper.... ive got a mity-vac kit that makes bleeding of system and bench bleeding the master a breeze..

TType_Riviera wrote:

they usually come pre bled dont they?? i just did rear hard lines on mine..bleeding was a breeze,changed out the old fluid too...the old stuff i bled out looked like coffee..lol brakes work twice as good now..except for the fact that i couldnt bleed the pass fron caliper cuz the bleeder broke off inside the caliper....yayyy i get to buy a new caliper.... ive got a mity-vac kit that makes bleeding of system and bench bleeding the master a breeze..

Every master I've seen, was an Automotive Service Manager for 11 years, came completely dry.
If you just replaced the line on the rear there would be no need to bleed the front. There are ways of getting broken bleeder screws out without having to replace the caliper! Try an easy out first.

I read up on 'bench bleeding' the master cylinder. Seems pretty cut and dry. Lotta pumpin and pumpin till everything flows nice. Sound like a typical evening for me. pimp

Hey rivman or anyone else, do you guys think I should just go an get a new Master Cyl or is a used one good enough. I havent heard of these going bad very often on these cars. Ed Morad has a used one for 20 bucks. Rock auto has a few versions for 50-100.

thanks for the help guys help

i got a reman for $35 from partsamerica.com. I got about 1100 miles on it so far no problems

urbsnspices wrote:

Hey rivman or anyone else, do you guys think I should just go an get a new Master Cyl or is a used one good enough. I havent heard of these going bad very often on these cars. Ed Morad has a used one for 20 bucks. Rock auto has a few versions for 50-100.

thanks for the help guys help

I'm not to sure I'd want to use an old master cylinder, but it isn't a hard part to change so if it didn't work it wouldn't be that much to change it again.

Be careful working with brake fluid. Don't let it touch skin or paint.

_________________
"An intercooled, supercharged, 280 HP Buick Riviera with neck-snapping acceleration and precise handling that proves GM can make something really interesting and competent, if only they would build more than one at a time."
- John R. White, Boston Globe

"I think that in any racing engine, the nearer you are to disintegrating, in general the better its performance will be."
- Keith Duckworth, Cosworth Engineering

'98 SC Riviera • 238k miles • 298 HP/370 LB-FT • 0-60: 5.79s • ET: 13.97 @ 99.28 • 4087 lb • 20.5 avg MPG

3.4" pulley • AL104 plugs • 180º t-stat • FWI w/K&N • 1.9:1 rockers • OR pushrods • LS6 valve springs • SLP headers • ZZP fuel rails
KYB GR2 struts • MaxAir shocks • Addco F/Rsway bars • ES links/bushings • GM strut brace • Enkei 18" EV5s • Dunlop DZ101 tires
F-body calipers • EBC bluestuff/Hawk HP plus • SS lines • slotted discs • ATE superblue fluid • DHP tuned • Aeroforce • Hidden Hitch

99Rivman wrote:

I'm not to sure I'd want to use an old master cylinder, but it isn't a hard part to change so if it didn't work it wouldn't be that much to change it again.

There 2 or 4 connections to the master cyl, right? When you swap it out, wont you get an air bubble at each connection?

I guess it would be good to fush the system again.

urbsnspices wrote:

There 2 or 4 connections to the master cyl, right? When you swap it out, wont you get an air bubble at each connection?

I guess it would be good to fush the system again.

In some cases you would be able to just crack the line at the connection and it get the biggest percentage of the air, but yes bleeding it all the way through is the best way.

Cool, I bought a new one from RockAuto. I am getting way to used to spending money on this car. dunno

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Write-Up: Brake Master Cylinder - Install & Bench Bleed

Write-Up: Brake Master Cylinder - Install & Bench Bleed

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