no brake system pressure after bleeding
 

I'd first like to thank Lyle for coming in from Connecticut and helping me out.

After completing installation of a new front pass side hard brake line, and front hoses, rear calipers and rotors, and bleeding the system 3 times with a Mity Vac, still no pressure, pedal drops to the floor. We think it may be air in the master cylinder.

What is the way to fix this?
Thx
B

The master cylinder can be bled while in the car, but needs to be level. It's easier to remove the master cylinder from the car and bench bleed it. In order to do that you need to get hoses to go from the hard line holes in the master cylinder to the reservoir to suck up fluid from it. I think you can buy a bench bleed kit at the auto parts store.

Can you borrow a pressure bleeder?

Sixto
87 300D

or make one? there is a GM brake res cap which will fit if you dont have an extra,(Mc PARTS) then as easy as adding a tire valve to it.
or like I did mine....w/ a gauge.

http://i42.photobucket.com/albums/e3...o/DSCN0997.jpg

http://i42.photobucket.com/albums/e3...o/DSCN0998.jpg


I tell ya these cars are a bear to bleed for some reason. I tried the one man jobber w/ the check valve on the end of a tube, the mity vac,etc, but the power bleeder is the way to go.

I would of bleed the master cylinder if we had more time

master cylinder is shot
 

It seems that the vigorous pumping of the brake pedal during our attempts to re-pressurize the cylinder and lines caused a rear circuit internal failure of the seals. Suggestions for next time would be to be more gentle when working on bleeding the brakes.
After an attempt to pressure bleed the entire system , the mechanic reported a master cylinder failure precipitated by over pumping of the pedal while the system had little fluid in it. So, a new master is on the way.
And still no car for another 3 days.

I used to always send the pedal to the floor when I bled brakes. Found out it was a bad Idea the hard way as well.

slow, regular distance pumps

Rule of thumb: Put your left foot under the brake pedal when you're foot-bleeding...

I used to put a scrap of 2x4 under the pedal to limit travel, but things are easier since I went to a Motive european pressure bleeder.:cool: I don't need to find anyone willing to help me either.:D

rebuild?
 

can the cylinder be rebuilt?

There are rebuild kits available, but I don't know what size you need, or where to find the specific kit for the w123.
http://www.stockcarproducts.com/master1.htm

You can buy rebuilt MC's too.

is it possible that I really don't need a master cylinder?
 

So, I've been thinking about this.

Re-manufactured calipers are honed out for the new cylinders to be put in, correct? Is it possible that the calipers themselves are not holding pressure?
The report was that the front brakes (old calipers) were ok, but the rears were not.
It was explained that there were 2 seals in the master cylinder and one could have failed or sprung off the piston thus causing the lack of brake pressure.
Is this probable? If the calipers are re-manufactured thus not within bore spec, could the caliper pistons not be holding in place ? and would that cause the spongy feeling.
What is the tell-tale sign of a MC failure? No pedal pressure or slight pedal pressure that goes down to the floor?

AFAIK, if the calipers aren't good they will visibly leak.

By chance did you evacuate the reservoir and refill before bleeding? Often this drains the rear half of the reservoir and there's a trick to getting it filled. Meanwhile your heavy pumping on the pedal sends air throughout the system making it that much more difficult to bleed. Hence the benefit of a power bleeder.

If time is not an issue, fill the reservoir to the brim and leave the problematic bleed valve open. See if you can get gravity to bleed that line for you.

None of this will help a bad master cylinder.

Sixto
87 300D

power bled, AFIK
 

So if the system won't hold any pressure, and all lines have been thoroughly bled, that means the master cylinder is toast?
Is there no other way to 100% determine if this is the case or it this a process of elimination type deal...