"simple" brake bleed- yeah right! help!

[slater]

Alright- Here comes some brake questions.

First, here's the story so far-
Wanted to bleed the brake system today. I had never had the brakes working properly, but it just felt as though they needed to be bled. I started out bleeding the back brakes first. The pedal would not get hard (at all), and I didn't really get much fluid out of the bleeders. I moved to the front, and got a lot of fluid out of the front. The pedal would now pump up and get hard, but loses pressure if you let it sit for a couple of minutes. So, I moved back and bled the back again, with the same relults. I bled on all again until I had nice new fluid coming out on all calipers. Still had a good amount of fluid coming out on front, and half as much on back. Pedal still gets hard and then loses pressure. The more times I bled, the less fluid I would get out on the back wheels, and the harder it would get to hold pressure in the pedal.
The pads in front are dragging a little bit, and the pads in the back are gripping full on. They seem to be able to move, as I can take it off and pry back the piston in if I open the bleeder.

Alright, so here's what I want to know-

1) Is the reason I am losing pressure in the pedal the master cylinder?

2) If so, is it worth it to pay twice as much to get a new one or is a rebuild kit okay?

3) Is there a way to test the M.C.?

4) If it is the M.C, why would I still get good flow out of the front but not the back?

5) How do you tell if it's time to rebuild the calipers?

6) Does anyone else have any suggestions cause I am about to freak out after 5 hours of brake bleeding.

[HarryD]

How do your rubber brake lines look? If they are old, I would suspect the rear lines are swollen and blocking flow and needing replacement.

[IROC]

Originally posted by slater
1) Is the reason I am losing pressure in the pedal the master cylinder?

Most likely. This is on a '67? Pull your carpets and driver's side floor board and look for any signs of wetness (brake fluid leaking from the master cylinder) around the pedal cluster.

"Losing pressure" means that the fluid is going *somewhere*. If this master cylinder is relatively old and you haven't been bleeding the brakes on a regular basis, then the simple act of bleeding the brakes can ruin the master cylinder. The cylinder bore develops some corrosion in the part where the piston doesn't travel too often (normal driving) and then when you start bleeding the brakes the piston moves over that corroded area and ruins the piston seals.

Anyway, I don't know if it's your master cylinder or not, but that would be something to check.

Mike

[Quicksilver]

Also check to see if the piston in the master cylinder is being fully released when you release the pedal. If the piston is partially depressed then the piston will be covering the reservoir port and it isn't going to bleed correctly and it is going to act odd in general.

It is probably more likely that the rubber lines are swollen or there is major gunk in the system.

Wayne

[slater]

Thanks for the info, guys... I think I am just going to place an order for a new M.C, rubber hoses, caliper rebuild kits, pads, and some better fluid. The brakes are not exactly something I want to have to worry about when i am driving down the road! Thanks!