Soft brake pedal


sitdusa
03-09-2006, 07:09 PM
98 Chevy Silverado K1500 5.7L Vortec, 177K.

I have a soft brake pedal and I noticed it about 45K ago when I changed the brakes on the front. I replaced the calipers, rotors, pads, and adjusted the back brakes. While the engine is off I have a firm pedal, but when I start the engine the pedal travels almost to the floor, I have bled the brakes, changed the Master Cylinder.

Any and all help is greatly appreciated!

Steve

GOLIATHGMC
03-09-2006, 11:38 PM
Assuming that nothing is leaking anywhere, there are two possibilities I can see. First one is about the bleed - After you did the work up front and bled the system, did you bleed all 4 corners or just the front? It is possible that ONLY bleeding the front might not be enough. Also, (in case you are unfamiliar) Bleed the corners in this order: RR, LR, RF, LF (furthest to closest to the master).
It is also possible that the replacement Master was bad, especially if it was a rebuilt from a store like Strauss or Auto Zone. Sometimes they get the bottom of the barrel in terms of rebuilders. You might also check the 3 soft brake lines in the system for bulges or damage.
Good luck, hope this helps.
George
REBEL Motorsports

2000CAYukon
03-10-2006, 01:38 AM
How far does your parking brake pedal move when you set the parking brake? If it goes to the floor and still not hold the truck, the rears are probably not adjusted properly.

You should be able to feel the brakes drag when you turn the wheel by hand.

//2000CAYukon

wedser
03-10-2006, 04:08 AM
after you have checked everything in the first post (espically where you got the master cylinder from and the bleed procedure/order) and that is all good you should replace the check valve that comes off the power booster, and goes to the intake manifold. I had to go to the dealer to get it and it took about 2-3 days but the normal autoparts stores did not carry the same check valve. i have a '97 silverado so it should be pretty close, and i had a slightly soft pedal but that check valve helped a lot.

Sam

offroadjoe
03-10-2006, 06:48 PM
Hey guys i got a 1988 sierra and i have the same problem but the pedal is soft even with the car off.. i have to pump it in order to stop alright... i got a master cylinder at a scarp yard, worked for a month than rigth back to pumping it than i bought a brand new one at c-tire.. but no same crap i bleed them twice after that same thing... i bought it about a year ago so i never really touched the front brakes but theres no leaks what do you think the problem is front brakes? i'm gunna go get them checked out later on this week i'm going to kill myslef lol ...

Mr. Smith
03-11-2006, 12:50 AM
98 Chevy Silverado K1500 5.7L Vortec, 177K.

I have a soft brake pedal and I noticed it about 45K ago when I changed the brakes on the front. I replaced the calipers, rotors, pads, and adjusted the back brakes. While the engine is off I have a firm pedal, but when I start the engine the pedal travels almost to the floor, I have bled the brakes, changed the Master Cylinder.

Any and all help is greatly appreciated!

Steve

I have found it you put a reman on (usually aluminum) they are junk in my opinion. I have noticed they bore and sleeve them. I guess the whole bore flexes causing internal bypassing of fluid.

The new cast iron units from Advance or Autozone work the best and with proper bleeding you can get a solid pedal. I have done my 97 and my buddies 91 with excellent results.

Bob B
03-11-2006, 10:58 AM
If you clamp carefully the flex hose in the rear lines, then test the pedal, This will eliminate the rears from the test and you might be able to decide which wheels are acting up. You can then do it to each front one at a time to eliminate them or not.
BTW the rears are self adjusting, but only adjust when applied while backing. So if you back up then pull it into drive, they aren't adjusting. If the parking brake takes a lot of motion to hold, this might be the problem.
Also spongy pedal means needs bleeding. Low but hard pedal menas need adjusting, I don't know if ABS affects those statements though.
Bob B

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