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

click to see write-up:
https://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.

E-brake is unrelated, separate issue.

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

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.

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

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

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.

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.

Look at it this way... drive her everyday and pay for gas, or let her sit and pay for parts. You end up paying either way!

AA wrote:

Look at it this way... drive her everyday and pay for gas, or let her sit and pay for parts. You end up paying either way!

You got that right, sometimes I forget that it is a 10 year old car.

And with gas prices at $3.50/gal, one could consider replacing parts to be an investment.

The brakes are practically gone, brake light beeping (but it stops if I fill up with brake fluid) Weird.

My Sunoco guy wants $500 to replace the master cylinder on my '95 Turbo Riv and Midas says $375...Looked up the part on Rockauto http://www.rockauto.com/catalog/raframecatalog.php. I'd like to buy the right part and spend the right amount of money on the mechanic.

Here are my questions: Do I buy the part and find a mechanic near me in Queens, NYC (hopefully, somebody on the Forum) or is this a big deal job? I'm thinking it's not but I"m not a mechanic and when most mechanics see a woman coming, they want to charge me triple.

But, I have this Forum.......so, that's not happening.

Any help is greatly appreciated!! Happy and safe driving!

In a nutshell you have 3 problems, none of which are that bad.

1) master cylinder replacement on a Riv requires that you "bench bleed" the thing, then install it - and then the entire brake system has to be bled; it's a good time to flush out all the fluid & replace with new. A 1-quart bottle of fluid will do it. The job does not take forever but done properly will take at least an hour but probably not much more, unless other parts are found to be broken or stuck like the bleed screws at the wheels for instance. Summary: it's not a quick job.

2) whatever you do, PLEASE don't buy an "economy" master cylinder. That said, a good rebuilt one (Cardone A-1) will be fine. NAPA will be fine if you get the better one. Beware of the cheap new ones. Your Sunoco guy knows you and is probably guessing his price on buying a Delco MC (you noticed on RockAuto they are not cheap). The Midas folks are probbaly using a rebuilt or economy MC. On the other hand, the MC used on the Riv is common to a whole bunch of other GM cars and as you saw on RockAuto is not necessarily all that expensive. Summary: the master cylinder that is installed will affect the price somewhat.

3) As for your question - I'd first find the mechanic and then buy the part. The mechanic you want to use may get the part at about the same price as you see on RockAuto becuase it's so common. So maybe you could print the list of parts from RockAuto and share that list with the mechanic - the two of you can then agree on what part to buy.

Albertj


Albertj

I would also look for an independent mechanic. It can be very hard to find a reputable independent though, you will have to rely on local GM owners to help you locate someone both knowledgeable and reputable. I recommend trying this site:

http://www.cartalk.com/content/mechx/find.html

and see what they have to offer in your area.

Most mechanics will not install parts that you provide, due to similar warnings as what albert mentions above. Find the mechanic, then find out if they will use a part you provide. Cheap parts make for unhappy customers down the road. Good parts make for good work and happier customers, except that the parts tend to cost more.

The other thing - don't be surprised to find that the leak is elsewhere, such as rusty brake lines or an issue in the ABS motor. Good ABS motors can be had used. Rusty brake lines are not all that hard to replace - the lines and fittings are not expensive, just need a mechanic who knows what he's doing to flare the lines properly.

With that list of brake MCs from RockAuto you and the mechanic you choose to use should be able to agree on parts. If he can get the parts for within 15% of the RockAuto price I'd let him do it if only because the *shipping* of the RockAuto parts will cost you extra anyway and by buying local the mechanic has someone local to deal with in the unlikely event there's a problem part. After all remember these MCs are pretty common across GM cars. Don't be surprised if mechanic picks the Raybestos, Bendix or Wagner MC with reservoir attached, and don't be surprised if he/she can get them locally for within 20% of the RockAuto price.

Albertj

Quote :

The brakes are practically gone, brake light beeping (but it stops if I fill up with brake fluid) Weird.

If it's leaking fluid, the master cylinder may not be the problem. There could be a leaking line, hose, or caliper. Need to identify where the fluid is leaking from before investing in parts or service. Brake fluid does not evaporate, so it must be leaking somewhere. Check tires and ground for clear liquid on insides of wheel.

AA wrote:

Quote :

The brakes are practically gone, brake light beeping (but it stops if I fill up with brake fluid) Weird.

If it's leaking fluid, the master cylinder may not be the problem. There could be a leaking line, hose, or caliper. Need to identify where the fluid is leaking from before investing in parts or service. Brake fluid does not evaporate, so it must be leaking somewhere. Check tires and ground for clear liquid on insides of wheel.

I had one MC (on an AMC) that leaked into the power brake booster. No visible drip, figured it out by elimination. That was a learning experience. Ended up putting on an MC and booster for a Buick Skylark (the 'late '60s versions).

Albertj

I just changed my MC this week. Replaced it with a brand new piece, easy as pie.