doorgunner

I completely rebuilt the brake system on my '68 convertible project, and it has worked perfectly for 3,000 miles/one year. No leaks/full master cylinder/17 "lbs." of vacuum at the manifold.

A few days ago the pedal started getting very hard. Now it has gone completely to the floor.

There are still NO signs of leaking anywhere/master cylinder is still full.

I have read about 15 threads on the subject before I do any troubleshooting.

Has anyone recently had a similar problem/What was the cause and solution?

Thanks in advance.

sparky77

Check you're rubber hoses first ,than you're master

dmaxx3500

slide the master cyl out of the booster,,just loosen the 2 nuts on the studes,and look for the back seal on the master,is it wet?

leaks into the vacumn booster are hard to find

Peterbuilt

Hi doorgunner,
A low pedal with no fluid loss might be caused by bearing run out,
have you rebuilt the trailing arm bearings?

doorgunner

I replaced all rubber hoses with quality U.S.hoses.

I'm out of town...I'll try it Friday.

Sure did.....I have rebuilt EVERYTHING on the car related to brakes/bearings/rotor face run-out/etc.

Thanks everyone for the replies....I'll update thread this Friday....also will keep checking thread replies until them.

doorgunner

Today/Sunday

Tested the master cylinder with the engine running = Pedal goes to floor.

-------------------------------------------------- off = Pedal goes to floor.

Pedal will not get firm by constant pumping with engine Running or Off.

I will unbolt master cylinder and check for fluid leaks.