Help Diagnosing brake problem

[smh292]

I have a 1971 LWB with manual brakes, discs up front and coils and drums in the rear. About a week ago I was driving and the pedal felt mushy. I opened the master cylinder and it was bone dry. I added some fluid to hopefully see where the leak is, and I cound not find it. I know I should bleed the lines and I plan on doing it this weekend, but while I was looking for leaks I looked up under the dash and the boot for the pushrod is shot and it looks like a little bit of fluid is coming into the cab.

That being said, I think the MC is bad and needs to be replaced, which is ok since i have a brake booster I plan to install so now I can get a new MC that is for power brakes. I believe the proportioning valve does not need to be swapped out.

I also plan to install new drums and shoes in the rear and rotors and pads up front.

What is still bothering me is why the MC was bone dry yet I can't see any leaks anywhere where that much fluid would go.

Any suggestions? Also, I'm wondering what order I should do all the replacement parts? Thanks for the help.

[WorkinLonghorn]

Well,I guess if you have fluid coming into the cab then that's the leak,unless one of the rear wheel cylinders is leaking a little. Did you remove the dust covers to see if they are leaking? Calipers can leak as can the lines themselves especially the rubber parts.
Make sure you replace or repair ("rebuild") the rear cylinders and the calipers.I use a little honing device I got for under $10 that has three stones,spring-loaded.
Bleed the MC 1st then the wheels.
There is a write-up on here somewhere for converting to vac-assist.

[smh292]

Do you think that much fluid would have leaked into the cab? The leak doesn't look that bad to make the MC bone dry.

[don t. - 72gmc]

When was the last time you checked the MC prior to the problem? If its been awhile, it could have leaked inside the cab. Pull the carpet/padding back and see how bad its stained.

As someone else said, check your rear wheel cylinders for leaks. Another easy place to look is the rubber hose that connects the hard line to the front calipers. Sometime there is no blo-back of oil to track.

HTH....good luck.....don t. .....

[Boog]

Pull up that rubber floor mat or carpet and look it over good. Brake fluid eats paint and the floor will rust if not attended to.
You know the master cylinder is bad so start with that one. If the rubber lines look like they need to be replaced then do it at this time. A new master cylinder will put more pressure on those hoses (moreso with the vacumn booster) and may cause one to pop on you. You won't like that.