Bad Booster (1 Viewer)

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May 20, 2011
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On my drive to work this morning I didn't have any power assist on the brakes until I had driven a bit. Do these trucks have any external check valve that could be causing this? It's like it had to warm up for the power assist to work. I figure either the booster is bad and some rubber parts eventually expanded due to the heat and sealed thus the brakes began to work or If there is an external check valve it was leaking and it took some time to build up vacuum. I don't hear any hissing or anything.
 
My booster recently went out. I replaced it with a Cardone reman unit. Cardone makes quality parts and is sold by Autozone, Oreilly's, etc.
 
There is a check valve located in the booster, check it first. Then check the hose for cracks as well. If those check out, it is most likely that your booster is actively failing. Mine did this for about 4 months before it finally stopped working completely. I went with Beno for the OEM booster replacement. If you go with the reman, make sure you check to ensure the push rod assembly is the correct length before putting everything back together.
 
check valve

So where is this check valve at exactly?
 
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BRAKE_BOOSTER_1FZ-FE.jpg
 
My brakes recently started acting up. Sometimes I have very little brakes and sometimes they work great. Maybe this is my problem as well
 
Update

Good news is the hard pedal is resolved...The bad news is that it now sinks to the floor and does absolutely nothing to stop the truck. Thank god I adjusted the handbrake. I seem to have an abundance of fluid in the resivoir as well. I wonder if something was dragging and the fluid boiled or something. Well I'll update as I dig in.
 
Good news is the hard pedal is resolved...The bad news is that it now sinks to the floor and does absolutely nothing to stop the truck. Thank god I adjusted the handbrake. I seem to have an abundance of fluid in the resivoir as well. I wonder if something was dragging and the fluid boiled or something. Well I'll update as I dig in.

Did you bleed the brakes?



If so you may have over-traveled the brake master piston. A high-mileage brake master will have a wear patrtern inside the bore in the normal travel distance. If the piston gets pushed past that (which often happens during agressive bleeding) it can take the seals out and the cylinder will leak down internally.
 
Did you bleed the brakes?



If so you may have over-traveled the brake master piston. A high-mileage brake master will have a wear patrtern inside the bore in the normal travel distance. If the piston gets pushed past that (which often happens during agressive bleeding) it can take the seals out and the cylinder will leak down internally.

Interesting, so agressive break bleeding can cause this! :eek: If this happens then the master cylinder will need replacement?
 
Interesting, so agressive break bleeding can cause this! :eek: If this happens then the master cylinder will need replacement?

That has been my experience.
 
I replaced my break lines with extended ones after my lift, and bleed the system with a self bleeder hand pump never exceeding 15PSI, always toping off the reservoir. Drove fine for a day or two, and now the pedal is Extremedly hard and there is no braking power. Reservoir is full of fluid.
SO Master cylinder or Booster? What is the most likely culprit? :popcorn:
 

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