Help: Brake pedal going to the floor - The 1947 - Present Chevrolet & GMC Truck Message Board Network

KEH · 07-11-2013, 06:03 PM

Most of the time I have good brake pedal, but every now and then it will go straight to the floor and pumping doesn't bring the pedal up. Fluid is full and pads are ok, so is this probably a master cylinder problem? Thanks for the help.

**Ol Blue K20** · 07-11-2013, 06:19 PM

Yes probably the master

68gmsee · 07-11-2013, 06:22 PM

I also agree with master cylinder being the problem. Don't use the truck until you replace it. It's a scary feeling when you suddenly lose brakes. Been there.

ole dollor · 07-11-2013, 06:38 PM

x 3 on the master cylinder .....

slikside · 07-11-2013, 07:02 PM

x4....if you are not loosing fluid, it's really the only thing that it can be.

Just replaced one on another vehicle with these same symptoms....cured it.

Side note: I was able to do this without bleeding the brakes in the traditional way. I just threaded the lines into the master cylinder (after bench bleeding, of course) barely hand tight. Then I had my daughter (12 years old) push the pedal to the floor and hold it there while I tightened up the lines (tighten, loosen, tighten, loosen, tighten....to make a good seal). She released the pedal. Then I topped off the m/c, and pushed on the pedal....good and firm it was!

Pushing the pedal with the lines only hand tight effectively bled that bit of air from the system. These instructions came with the new m/c. Seemed so simple, and it was. I was thinking I would have to do a complete bleed, but it wasn't necessary.

KEH · 07-11-2013, 07:05 PM

Thanks I appreciate the confirmation!
Posted via Mobile Device

KEH · 07-11-2013, 07:07 PM

Thanks Slik I will give that a try.
Posted via Mobile Device

68gmsee · 07-11-2013, 07:11 PM

Quote:

Originally Posted by slikside

......Pushing the pedal with the lines only hand tight effectively bled that bit of air from the system. These instructions came with the new m/c. Seemed so simple, and it was. I was thinking I would have to do a complete bleed, but it wasn't necessary.

Taking advantage of your daughter? My kids are all grown and gone and my wife tries to hide when I work on my brakes.

That bleeding technique makes sense. Wish I had known to do this before. I'm so used to doing it the old way I just don't read instructions. I guess I need to.

slikside · 07-11-2013, 09:22 PM

Quote:

Originally Posted by 68gmsee

Taking advantage of your daughter? My kids are all grown and gone and my wife tries to hide when I work on my brakes.

That bleeding technique makes sense. Wish I had known to do this before. I'm so used to doing it the old way I just don't read instructions. I guess I need to.

Trust me, it wasn't without complaint!!

07-11-2013, 06:03 PM	#1
KEH Better late than never Join Date: Dec 2001 Location: Columbus, IN Posts: 324	Help: Brake pedal going to the floor Most of the time I have good brake pedal, but every now and then it will go straight to the floor and pumping doesn't bring the pedal up. Fluid is full and pads are ok, so is this probably a master cylinder problem? Thanks for the help. __________________ 1970 C/10 SWB Stepside

07-11-2013, 06:19 PM	#2
Ol Blue K20 Proprietor of Dale's Corner Join Date: Nov 2012 Location: Vacaville , CA Posts: 15,969	Re: Help: Brake pedal going to the floor Yes probably the master __________________ "Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man

07-11-2013, 06:22 PM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Help: Brake pedal going to the floor I also agree with master cylinder being the problem. Don't use the truck until you replace it. It's a scary feeling when you suddenly lose brakes. Been there. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

07-11-2013, 06:38 PM	#4
ole dollor Registered User Join Date: May 2012 Location: Anton, Texas Posts: 2,364	Re: Help: Brake pedal going to the floor x 3 on the master cylinder .....

07-11-2013, 07:02 PM	#5
slikside Registered User Join Date: Jun 2010 Location: San Diego Co. Posts: 1,157	Re: Help: Brake pedal going to the floor x4....if you are not loosing fluid, it's really the only thing that it can be. Just replaced one on another vehicle with these same symptoms....cured it. Side note: I was able to do this without bleeding the brakes in the traditional way. I just threaded the lines into the master cylinder (after bench bleeding, of course) barely hand tight. Then I had my daughter (12 years old) push the pedal to the floor and hold it there while I tightened up the lines (tighten, loosen, tighten, loosen, tighten....to make a good seal). She released the pedal. Then I topped off the m/c, and pushed on the pedal....good and firm it was! Pushing the pedal with the lines only hand tight effectively bled that bit of air from the system. These instructions came with the new m/c. Seemed so simple, and it was. I was thinking I would have to do a complete bleed, but it wasn't necessary. __________________ 1972 Chevy C-10, SWB, Fleet, 350/350, PS, PB, all stock, Survivor.

07-11-2013, 07:05 PM	#6
KEH Better late than never Join Date: Dec 2001 Location: Columbus, IN Posts: 324	Re: Help: Brake pedal going to the floor Thanks I appreciate the confirmation! Posted via Mobile Device __________________ 1970 C/10 SWB Stepside

07-11-2013, 07:07 PM	#7
KEH Better late than never Join Date: Dec 2001 Location: Columbus, IN Posts: 324	Re: Help: Brake pedal going to the floor Thanks Slik I will give that a try. Posted via Mobile Device __________________ 1970 C/10 SWB Stepside



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