Brake issue/problem

Pleil

Pleil

Member
Hi all my 79 Scout II has been having some brake problems. First all the booster and master cylinder are new within the last year or two and hasnt been drivin hardly untill just lately. The pedal seems to be hard and sometimes I notice if I let off the brake, it very very slightly stays on and I can lift the pedal with my foot and then slightly roll...also I noticed the master is leaking around most of the top. The seal and rubber is definately tight so that makes me wonder. Thanks for any help!!:icon_neutral:
 
Did you bench bleed the master? How about the lines at the wheel cylinders? By new do you truly mean new or are the parts actually reman? The quality of reman brake components is generally in the toilet these days.
 
I tried the booster test where you pump with the truck off and start..the pedal went down so im reading that means its good. So narrowing it to the master maybe a line is clogged or air? Anyone?
 
You can always try bleeding the lines some more, but if that doesn't help and you don't have any leaks at the wheel cylinders/calipers, you've pretty much isolated your issue.
 
So I checked all my brakes and nothing is seized or leaking. Im waiting for my new master from ihon to come in. I noticed today when I took off the valve on the booster, pressure came out. The truck was sitting for 24 hours or so. Shouldnt that bleed off? Is that right?
 
pleil said:
so I checked all my brakes and nothing is seized or leaking. Im waiting for my new master from ihon to come in. I noticed today when I took off the valve on the booster, pressure came out. The truck was sitting for 24 hours or so. Shouldnt that bleed off? Is that right?
Click to expand...

If you are referring to the check valve where the vacuum hose attaches, then pressure (atmospheric pressure) went in.
That is a good sign that your check valve & vacuum booster are not leaking.
The brake booster works by having a low pressure on the forward side of a diaphram, when you step on the brake pedal, atmospheric air pressure (14.7 psi at sea level) enters the back side of the chamber (from inside the cab) and pushes the diaphram forward, assisting you in pushing the brake rod into the master cylinder.
 
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