Brake System repair- Update - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Coley · 11-27-2017, 02:32 PM

I posted a few weeks ago about a problem I was having with the brakes on my '72 in terms of a pedal that would 'drop' over time (10,20 seconds,etc) but would grab again as soon as it was pumped....and there was no loss of fluid within the system.... as well as very 'grabby' brakes.
A few of you guys mentioned that this appeared to be a master cylinder (internal leaking) issue so, as recommended.....I changed out the master cylinder Yesterday.

Well...quick update, it went great...pretty straight forward.
I picked up a new master cylinder yesterday morning....removed the old one, bench bled the new one...and had it all done within a couple of hours.
The net result was great.
No more 'sinking' pedal and the sensitivity issue seems to have gone away as well.
I will get bleed the brakes further but at this point....waayy better and many thanks for the input and advice.

Here are a few quick pics of the process....very straight forward stuff. In the pics you can see the old master cylinder....and I used a syringe to remove most of the brake fluid prior from removing it from the truck, which reduced the dreaded 'drip' of brake fluid, etc around all the paint.

As for the old master cylinder? I took it apart and it was definitely pitted in the bore in a couple of key places and the seals look none the worth for wear....plus it was pretty dirty.

So....at this point, back on track....although the truck is now off the road for the season so it won't be seeing any more road time until spring except for one planned trip to the painters....but more on that later.

Coley

**dflarsen77** · 11-27-2017, 03:50 PM

How old was your master cylinder?

weq92f · 11-27-2017, 03:58 PM

Sweet, thanks for the update!

-klb

Coley · 11-27-2017, 04:02 PM

Age of the master cylinder?....I have no idea but it was on the truck when I bought it about 7-8 years ago. The trucks odo shows around 130K miles...which I'm pretty sure is original based on the trucks overall condition.
I'm not sure how long they last...maybe it was the original?...or might have been changed out again 20-25 years ago.
Hopefully the new one is good for another 10 years....if not, no problem....it was a pretty straight forward repair.

Coley

11-27-2017, 02:32 PM	#1
Coley Registered User Join Date: Oct 2011 Location: Victoria, B.C Posts: 3,794	Brake System repair- Update I posted a few weeks ago about a problem I was having with the brakes on my '72 in terms of a pedal that would 'drop' over time (10,20 seconds,etc) but would grab again as soon as it was pumped....and there was no loss of fluid within the system.... as well as very 'grabby' brakes. A few of you guys mentioned that this appeared to be a master cylinder (internal leaking) issue so, as recommended.....I changed out the master cylinder Yesterday. Well...quick update, it went great...pretty straight forward. I picked up a new master cylinder yesterday morning....removed the old one, bench bled the new one...and had it all done within a couple of hours. The net result was great. No more 'sinking' pedal and the sensitivity issue seems to have gone away as well. I will get bleed the brakes further but at this point....waayy better and many thanks for the input and advice. Here are a few quick pics of the process....very straight forward stuff. In the pics you can see the old master cylinder....and I used a syringe to remove most of the brake fluid prior from removing it from the truck, which reduced the dreaded 'drip' of brake fluid, etc around all the paint. As for the old master cylinder? I took it apart and it was definitely pitted in the bore in a couple of key places and the seals look none the worth for wear....plus it was pretty dirty. So....at this point, back on track....although the truck is now off the road for the season so it won't be seeing any more road time until spring except for one planned trip to the painters....but more on that later. Coley Attached Images __________________ ....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500

11-27-2017, 03:50 PM	#2
dflarsen77 Active Member Join Date: Jun 2016 Location: Salida, CA Posts: 177	Re: Brake System repair- Update How old was your master cylinder? __________________ David Larsen 1970 Chevrolet C-10

11-27-2017, 03:58 PM	#3
weq92f Registered User Join Date: Oct 2016 Location: Dallas Texas Posts: 3,218	Re: Brake System repair- Update Sweet, thanks for the update! -klb __________________ 67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold

11-27-2017, 04:02 PM	#4
Coley Registered User Join Date: Oct 2011 Location: Victoria, B.C Posts: 3,794	Re: Brake System repair- Update Age of the master cylinder?....I have no idea but it was on the truck when I bought it about 7-8 years ago. The trucks odo shows around 130K miles...which I'm pretty sure is original based on the trucks overall condition. I'm not sure how long they last...maybe it was the original?...or might have been changed out again 20-25 years ago. Hopefully the new one is good for another 10 years....if not, no problem....it was a pretty straight forward repair. Coley __________________ ....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500

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