M35A2 brakes have changed good bad?

[ohnuts]

Did a hand over hand check of brake lines and found an airlne that was not crimped into its ferrul tube and connector. Since the original build the Two pipes had so much tension towards each other that little air was actually lost.

Question. Replaced bad ferrul ring and connector and the air pressure has now gone from 85 to 110. The presure comes up faster and bleeds off less when the truck is turned off.

This is the change.

On the first run of the truck after the repair, the brake pedal went to the floor with no action in the pedal. After ten pumps the pedal does pump up and gets hard and holds with no bleed down. The brakes do seem more responsive at 110 psi but when you let up on the brake pedal there is a marked vent sound.

Question (1) was that sound there all the time but my borderline presure before just didnt give much voice to it?

Question (2) did the air pac charge higher than normal because of the higher air pressure and drop the fluid in the master cylinder (will check this).

Just went out and tried the brake pedal, truck has been off for five hours and brake pedal is hard and holds firm without running the truck.

Ideas?

 

[gimpyrobb]

The vent sound is normal. Check the fluid level in your master.

 

[m16ty]

If you have to pump up the brakes it could be a number of things. My first guess would be air in the system after I checked that I'd make sure the brakes are adjusted. If you still have to pump them it could be the master cylinder (this is kind of rare).

It is normal for the pedal to be more firm with no air than it would be with air pressure in the system.

 

[badgmc56]

Brake adjustment should be done first before bleeding unless you are pressure bleeding then you can get away with it. Most low pedal problems are caused by incorrect brake adjustment. There are no self adjusters in these systems. Unless you have run out of fluid because of a leak ,bad master, airpack,wheel cylinder, air in the system should never be a problem.