Brake Master Cylinder Question
 

anybody know how to replace one on a GM vehicle with TCS? the haynes manual says to have it done by a qualified repair shop that has a Tech-1 or T-100 tool for proper bleeding.

thoughts?

What's TCS? I've done many GM master cylinders over the years, I've never needed any special tools though.

-Jay

traction control system

I have found that the best way to bleed master cylinders, whether clutch or brake is to run a hose from the bleeder to a jar with some fluid in the jar. Fill the reservoir and pump the pedal several times to flush the circuit.

Pressure bleeding will not get air pockets out of lines that have vertical sections. learned this the first time I bled a 300 ZX twin turbo. Pressure bleeding just wouldn't get the pedal pressure working properly.

Also found it necessary when I converted my 76Z to rear disc brakes.

It's also a one man job, just keep the end of the hose submerged in the fluid in the jar.

Its more a flushing process than a simple bleeding process, and you can easily see when you have clean fresh fluid.

If you are bleeding or flushing an old master cylinder, avoid pushing the pedal all the way to the floor. Instead try to keep the range of pedal motion the same as you would in normal brake application.

You ask why?

Simple, when you push the piston into areas it has never travelled you exponentially increase the risk of failure, due to the fact that the lower areas of the cylinder have not had the piston move across them. Many times this will prevent you from having to replace the master cylinder when it fails while you are bleeding the brakes.

There is a logical argument that if that happens, it should be replaced anyway, and I agree with that logic. The problem is when you have a customer on a very limited budget who just can't afford a new master at that time. I have actually taken the master out of my car and put it in the customers car on one occasion when that happened. Just put a new one in my car even though it was only a couple of years old.

That customer and I grew old together and she knew we would not take advantage of her or anyone else for that matter.

regards
gary

Sorry, can't help you on that one... My family has never owned a GM vehicle with that.

R.I.D.E.,

thank you for your response.

i have a bleed kit that i've used many times. it's a simple jar w/magnet(to keep the fluid above bleeder valve presumeably) and hose for the fitting. i like the simplicity of the manual bleed(flush) as well!

my concern is the ABS and TCS. it's my wife's car and certainly pertains to the safety of she and the kids. BTW, the "brake" light is illuminated constantly and the "ABS" intermitantly.

Last time I dealt with any GM master cylinder, I submerged the whole thing in fluid and bled it through like that.

using tech 1 it will run the abs pump that will help get the air out i think. also on some lincolons/fords using NGS/WDS , the pump runs for a few seconds as you bleed the system. I think some air may be trapped in the pump motor, this way the sys. is activated and any air can pass through it.

If it is like my Lincoln with ABS, you just sort of drive it and the air works out of the system. The Lincoln manuals gave all sorts of dire warnings and consequences of not following their procedures...for me the pedal firmed up pretty quickly. Watch the fluid level.