Brake pedal fade

[VDOG]

Ok I have read some of the previous post on brake pedal fading.
And I would agree that the master cylinder is the problem. But I had a new master installed about 4 years ago and still had pedal fade so it was found that I needed wheel cylinders. My truck might have 1000 miles on it since the master install. Change the wheel cyl's and added front disc brakes.
Now I know I need a booster for real stopping power but until then I should not still have the same problem of pedal fade. help!!

[ChevLoRay]

What happens to your pedal that you are calling "fade"?? If the pedal is slowly going to the floor while your foot is pushing on it, is that what you call fade?

Usually brake fade is the action of the actual friction going away because the brakes are hot. Drum brakes are more notorious for this, and is why we have disc brakes on vehicles today.

It may be a matter of semantics, but the words we choose to use can make a big difference in the caliber of help that we get.

[VDOG]

Originally Posted by ChevLoRay

What happens to your pedal that you are calling "fade"?? If the pedal is slowly going to the floor while your foot is pushing on it, is that what you call fade?
It may be a matter of semantics, but the words we choose to use can make a big difference in the caliber of help that we get.

I see your point. Ok when I come to a complete stop and hold my foot on the brake, they slowly sink to the floor. If I pump them up while still at the light, they pump up, then start to sink slowly to the floor again.

[PanelDeland]

VDOG, are you having to add fluid?If not then you either have a bad MC or the fluid is leaking past the seals in the wheel cyl/calipers and hasn't built up enough to leak out.The only way the pedal will fade(I usually call this pedal fade as opposed to brake fade when the brakes don't stop as well)is if there is somewhere for the fluid to go i.e. past the piston in the MC or one of the wheel Cyl or calipers.I would guess the MC but if you are losing fluid it may be the wheel cyl or the hoses.Crawl under the truck and check for brake fluid around all the fittings/lines and also at the brake drums/calipers.If you see no fluid then the MC can be partially checked by having someone stand on the brake while looking into the MC.You "MAY" be able to see the fluid coming from the port back into the MC.
You might also check the hoses while having someone stand on the brakes.If they expand this may be causing your symptom.
The only other thing I can think of is air in the system and that would require bleeding.

[VDOG]

Originally Posted by PanelDeland

VDOG, are you having to add fluid?If not then you either have a bad MC or the fluid is leaking past the seals in the wheel cyl/calipers and hasn't built up enough to leak out. require bleeding.

Nothing leaks, brakes have been bleeded, rear wheel cyls are new along with disc brakes. Now I have not adjusted the brakes when I installed the new drum brake hardware. Or are these self adjusting?

[ChevLoRay]

If nothing leaks, and the pedal slowly goes to the floor, then brake fluid is going somewhere. As PanelDeland suggested, there may be issues with the master cylinder. Self-adjusters don't have any effect on what you are sensing.

By the way, self-adjusters (when installed properly) will adjust each time you use the brakes to slow/stop the vehicle as you are backing up. That is how they are designed to work. Pumping the brake pedal to bring the pedal back up indicates a loss of pressure within your system. If you cannot find any evidence of a leaking wheel cylinder and there has been no loss of brake fluid from the master cylinder, then it may be time to install another master cylinder. If you paid someone to replace it, you should take it back to them and have them check it out.

[VDOG]

Originally Posted by ChevLoRay

it may be time to install another master cylinder. If you paid someone to replace it, you should take it back to them and have them check it out.

Im going to pick up a new master and booster this weekend and I hope that solves the problem. Thanks guys.