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Brake problem?

cwalton

cwalton

1/2 ton status
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Mar 7, 2012
Posts
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Location
Andover, NH
When I depress my brake pedal, it doesn't feel like there is much resistance and i decelerate very slowly. I don't expect 1971 brake set ups to be the best, but something doesn't feel right. I do not know a whole lot about brake systems so bare with me.

As you can see in the first picture, one of the compartments was empty of brake fluid, i don't believe it is supposed to be. I've topped that off now, and looked for leaks but haven't found anything. Secondly on the cover (3rd pic); the expandable rubber thing. is that supposed to be folded in? I'm pretty sure its not supposed to look the way it does now, so I popped it down.

That's what I've come across so far. Please let me know if I'm looking at things right or wrong, and any other suggestions to what the issues may be!

2012-09-26_09-12-42_847.jpg

2012-09-26_09-13-03_554.jpg

2012-09-26_09-13-13_821.jpg
 
that front reservoir is NOT supposed to be empty, so filling it up was the right call. The reason your rubber seals on the lid were down like that was because the fluid was low. Check near the wheel cylinders on your rear brakes. Those are a likely culprit for leaks. They should be perfectly dry (and below them on the drum backing plate). If they are not, then there is a leak.

Since you ran that reservoir dry, you'll need to rebleed your brakes too. That should make a huge difference in your brakes.
 
Yep. From the looks of the fluid I would suggest using a turkey baster and sucking all that old,black fluid out re-filling the resv then bleeding the system until clean clear fluid comes out of each wheel. It is not all that hard to do and it will help you be a bit more familiar with your truck and brakes.
 
I agree with all thats been said.

fluid looks very dirty, I would empty it out and replace it, then bleed, bleed, bleed. the front section going empty likely has put air in the lines accounting for your soft pedal and weak braking.

Im assuming you know the process for bleeding the brakes? if not I'd be happy to go through the process. just dont wanna sit here and tell you something you already know.

likewise, if that much fluid disappeared, there has to be a leak somewhere. the trick is to find it.
 
I'll betcha it turns out to be a bad brake booster......

A leaking master cylinder will wipe out the booster soon after.


I had hard, ineffective brakes on my old Burb. Swapped the MC first but it didn't make any difference to the pedal feel or ability to bleed the brakes effectively. The new booster was the answer, and once that was swapped in the brakes were nice and strong again.


-G
 
How long does it usually take to bleed off the brakes if the lines went totally dry? I changed out both the rear wheel cylinders and a piece of brake line that had a small weeping hole just above the rear axle. I got one of those little vacuum pumping kits so i could bleed them on my own, and it seems to be sucking an awful lot of air out and not fluid so far. Should I be expecting it to take forever to refill the lines, or should I start looking for another problem?
 
should be fairly quick. Just a few pumps of the pedal should do it unless you are somehow sucking in more air. Make sure air isn't coming back in when you release the pedal, and also be sure you don't let the MC get low enough to let air in.
 
ashman said:
should be fairly quick. Just a few pumps of the pedal should do it unless you are somehow sucking in more air. Make sure air isn't coming back in when you release the pedal, and also be sure you don't let the MC get low enough to let air in.
Click to expand...

Yeah i must be sucking in air from somewhere then, cause it was way more than a few pumps, & the vacuum pump eliminates the potential for sucking air in when the pedal releases. The MC level didnt go down much at all either, so i guess ill have to investigate where air is being sucked in from
 
The rubber on the underside of the lid to the master cylinder should be collapsed like an expandable plastic drinking glass that is flat. I would also check the rubber grommet around the vacuum hose on the brake booster. If that is leaking it can cause poor braking.
 
I've decided to just go ahead and order up new rear brake lines, a new MC and vacuum booster. "Might as well" get it all done at once so I don't have to deal with it this winter... blah...winter...I need to get out of the north east. :doah:
 
Probably not a bad strategy...

Braking systems are one of the most abused and disrespected systems on on vehicles. Nobody ever seems to flush their fluids, EVER and the system gets completely corroded and full of crud that eats up all the seals, etc.

I replaced the mc/booster on my old Burb and flushed all the lines thoroughly and it made a HUGE difference. I'm sure you'll have a similar experience.


-G
 
Greg72 said:
Probably not a bad strategy...


I replaced the mc/booster on my old Burb and flushed all the lines thoroughly and it made a HUGE difference. I'm sure you'll have a similar experience.


-G
Click to expand...

Sounds good. Is there any particular trick to swapping out the booster/MC I should know about it? this will be my first swap for this, so any direction would be helpful
 
Search for instructions on bench bleeding the master. It's a lot easier to get the air out before its bolted in place.

Also, paint it before installation. It will look good initially but they are just raw metal and rust up almost instantly and look terrible from then on.

-G
 
Greg72 said:
Search for instructions on bench bleeding the master. It's a lot easier to get the air out before its bolted in place.

Also, paint it before installation. It will look good initially but they are just raw metal and rust up almost instantly and look terrible from then on.

-G
Click to expand...

Sounds good, thanks man. Would I be able to find that stuff by sorting through my horribly organized assembly or chassis repair manuals? Though suppose google would probably solve my problems like it always does anyways haha.
 
naaa, it won't be in yoru assembly manual, but likely it will be on the papers that come with your new MC.
 
About how long does it take to swap out a vacuum booster? I was reading for the new model GM's its about a 5 hour job?
 
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