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Brake issues on a truck

Posted: Mon Jul 01, 2013 11:24 am
by Ls7camaro
Hey All.

I have a 1994 chevy C1500 Silverado, I have been trying to get the brakes sorted out for some time now.

I replaced all the lines / calipers / pads / rotors / wheel cylinders / master cylinder. only thing not replaced is the Booster/prop valve/ABS.

If the truck is not running, the pedal is good/firm, once you turn the truck on, the pedals hits the floor. Is this the booster valve? Booster? ABS?

Can I bypass the ABS? Is it needed for what I am using the truck for? Gonna be used to pull trailer/haul stuff.

I have bled the brakes a number of times. Any help is good, thank you.

Re: Brake issues on a truck

Posted: Mon Jul 01, 2013 1:53 pm
by John_Heard
Sounds like you still have air in the lines to me..

Re: Brake issues on a truck

Posted: Mon Jul 01, 2013 2:01 pm
by Ls7camaro
John, I bled these a number of times. No chance it is the booster? Or check valve on booster?

I started at the back rear, worked my way forward. It does have the rear wheel anti lock brakes system. Could that be an issue?

Re: Brake issues on a truck

Posted: Mon Jul 01, 2013 2:18 pm
by John_Heard
If the booster was leaking, it should make the pedal stiff. All it does is reduce your pedal effort.

I don't know anything about these late model anti-lock setups, maybe one of the other guys does, it certainly sounds like there's air in the system to me.

Re: Brake issues on a truck

Posted: Mon Jul 01, 2013 2:30 pm
by Ls7camaro
Ok. Is there a better way. I know the truck is on an incline, would that make a difference? There is a whooshing sound when you pump the brakes. I put a remaned master cylinder on and bench bled it. Just getting to be at a loss.

How about a vaccuum bleeder?

Re: Brake issues on a truck

Posted: Mon Jul 01, 2013 3:05 pm
by John_Heard
Personally I hate to bench bleed master's, seems like that has always screwed up remanufactured ones for me - perhaps they don't machine bore deep enough - rough machining? I don't know, but I quit doing it. I just put it in the car and vacuum bleed them using a mighty vac deal and usually without too much effort it works fine.

The whooshing sound is probably air rushing into the booster from so much travel going on.

Re: Brake issues on a truck

Posted: Wed Jul 10, 2013 11:45 am
by Ls7camaro
So got frustrated and took the truck to a shop. Multiple issues. First, ABS to the RWAL needed bled out/reset, so by driving this reset it. There was still a bit of air in the rear lines, We bled the brakes over and over. Last, the rear drums where way out of adjustment. Causing the pedal to go to the floor.

The ABS, I know I couldn't do anything about, just had to drive it a bit. The air though, I am dumb founded. The rear adjustment, I had the same problem on my mini van, and fixed it, I never would have thought it was that.

Off to work on the disk brakes for the Camaro, after I do some more mechanical work on the truck.

Thank you all for the tips/help.

Next, flush the cooling system, new thermostat and so on. Does anyone recommend flushing the transmission?