GSL-SE: Master cylinder bleeding?
 

The car is suffering from a super soft brake pedal and since there is no obvious leak, I figure it's the master cylinder. I got a refurbished one and now wonder whether I need to bleed the master cylinder before installing it. If so, I'll have to look around for some suitable plastic connections and hoses.

bench bleeding is the best way.

Example:

Personally I always install the M/C and just use it to bleed all the lines starting with at the furthest point from the M/C.

Two person job though... Need someone to pump the brakes and someone to open and close the shrader.

I use a brake bleeding kit from Harbor Freight. Only one person needed and I can do the entire system in 10 minutes. You will need an air compressor. I crank it up to 100psi.

Brake Fluid Bleeder

i use the same HF one man bleeder. works very well

Guess who's going to HF on fri? ;)

We actually use a mityvac in the moto shop I work at. This looks like a HF knockoff of it. Awesome tool to have, but its still nice to have a person filling the resivior while one sucks out the line with this bleeder.

I agree. I hate spilling brake fluid because it's so corrosive. Always a good idea to have someone monitoring the fluid level.

Thanks for this!

So you don't bleed the Master cylinder on its own beforehand?

bench bleed is quicker but i prefer a full bleeed to ensure fresh fluid and not mixing different brands of brake fluid

I don't. With the HF bleeder, there's no need. It sucks the fluid through at a fast pace there's really no need. One thing I found is that you need to crank up the air pressure for it to work good. We changed the master on my Dads 1985 GSL-SE and it took all of 10 minutes. He's 71 years old and doesn't really like sitting in the car pumping the brakes to bleed them.

Okay, new master cylinder is in. I haven't completely bled the brakes yet but the pedal still goes to the ground very easily. It almost seems like there is no fluid in the lines. However, since I see no puddles I have to assume there is no leak.

Are these ALL the possible reasons for a soft pedal:

1) air in the system
2) bad master cylinder
3) fluid leak in the system

If there isn't anything else, then I'll continue working with 1).

I would say its probably #1 although you won't know for sure until you finish bleeding.

youre doing a half ass job. bleed it completely

Without bench bleed you're gonna need a couple pints fluid, lotsa leg energy, an understanding helper, and an hour to bleed that system. Or a vacuum bleeder. Still gonna take time and fluid.