Brake question??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

kevmic28 · 12-13-2010, 05:45 PM

70 GMC drum brakes non powered.
I have replaced in the last year:
Master cylinder
All 4 wheel cylinders
All new rubber hoses
Now question is:
The other day I was driving and the pedal went to the floor. I let off and pumped it once and it was back to normal. Now occasssionally it will do it but not regularly. No leaks anywhere. Reblead the system. adjusted the adjusters to make sure they were where they were suppose to be. Brake pads are good. looked inside the brakes to make sure the wheel cylinders are not leaking.
What could be causing this? Bad master cylinder possibly?

Wrenchbender Ret · 12-13-2010, 06:21 PM

Make sure the brakes are adjusted good & all the mechanical parts are good . Sometimes a rod from the wheel cyl. does not get put in the slot on the shoe. If all that is good you have a bad master cyl.

BB72CHEVKT · 12-13-2010, 06:40 PM

My guess would be the m/c again. The one I got from Autozone lasted a whole year and I had the same symptoms.

rusty baker · 12-13-2010, 07:41 PM

The first MC that I got from Autozone was bad too.

kevmic28 · 12-13-2010, 08:08 PM

All the parts have been on for better part of a year. So Im thinking MC too. The one on there I got last summer from Advanced auto.

12-13-2010, 05:45 PM	#1
kevmic28 Registered User Join Date: Jun 2009 Location: Arlington Texas Posts: 602	Brake question??? 70 GMC drum brakes non powered. I have replaced in the last year: Master cylinder All 4 wheel cylinders All new rubber hoses Now question is: The other day I was driving and the pedal went to the floor. I let off and pumped it once and it was back to normal. Now occasssionally it will do it but not regularly. No leaks anywhere. Reblead the system. adjusted the adjusters to make sure they were where they were suppose to be. Brake pads are good. looked inside the brakes to make sure the wheel cylinders are not leaking. What could be causing this? Bad master cylinder possibly? __________________ 1970 GMC truck 1988 Harley 1200 Sportster

12-13-2010, 06:21 PM	#2
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,208	Re: Brake question??? Make sure the brakes are adjusted good & all the mechanical parts are good . Sometimes a rod from the wheel cyl. does not get put in the slot on the shoe. If all that is good you have a bad master cyl.

12-13-2010, 06:40 PM	#3
BB72CHEVKT Junior Member Join Date: Mar 2007 Location: Hideaway, TX Posts: 4,950	Re: Brake question??? My guess would be the m/c again. The one I got from Autozone lasted a whole year and I had the same symptoms. __________________ 71 Suburban 350/700R4 Project Trixie 72 CHEVY,Highlander,SWB,396,T400

12-13-2010, 07:41 PM	#4
rusty baker '70 C-10 Primer Join Date: Dec 2008 Location: nevada,missouri Posts: 117	Re: Brake question??? The first MC that I got from Autozone was bad too. __________________ "The difference between stupidity and genius is that genius has its limits." Albert Einstein

12-13-2010, 08:08 PM	#5
kevmic28 Registered User Join Date: Jun 2009 Location: Arlington Texas Posts: 602	Re: Brake question??? All the parts have been on for better part of a year. So Im thinking MC too. The one on there I got last summer from Advanced auto. __________________ 1970 GMC truck 1988 Harley 1200 Sportster



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