need help with drum brakes
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Posting Guru
Joined: Mar 2006
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need help with drum brakes
scratching my head on this one.
a couple of months ago, i replaced all 4 wheel cylinders, and put in a lightly-used master cylinder that had been sitting on the shelf. everything was good.
last weekend, suddenly experienced a loss of pedal pressure- now have to pump the brakes. can't find any leaks.
i cracked open the master cylinder- the fluid in the rear bowl is clear as a bell. the front bowl was very cloudy, and had sediment in it.
i cleaned the front bowl, re-bled the lines, but still have to pump the brakes.
any ideas?
a couple of months ago, i replaced all 4 wheel cylinders, and put in a lightly-used master cylinder that had been sitting on the shelf. everything was good.
last weekend, suddenly experienced a loss of pedal pressure- now have to pump the brakes. can't find any leaks.
i cracked open the master cylinder- the fluid in the rear bowl is clear as a bell. the front bowl was very cloudy, and had sediment in it.
i cleaned the front bowl, re-bled the lines, but still have to pump the brakes.
any ideas?
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
Brakes are the most important system on any vehicle. Don't try to short cut or cheap out by reusing old MCs or buying rebuilt MCs. Always buy NEW MCs.
The problem is most likely that your reused MC is bypassing internally. This is why you can't find any leaks but why you are having to pump the brake pedal to build system pressure.
Senior User
Joined: Sep 2009
Posts: 474
Likes: 3
From: Central Wisconsin
Maybe the MC had a slight blockage. It allowed enough fluid through it to work for a while.
How many times do you have to pump before you get decent brake pressure?
I have drums and build pressure with 2 pumps, and the third is my holding pressure.
How many times do you have to pump before you get decent brake pressure?
I have drums and build pressure with 2 pumps, and the third is my holding pressure.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Hmm ya should not have to pump the pedal to build it up. The 2nd or 3rd pump may be when you hit a little kid running out in the street. Like op say brakes most important thing on a vehicle.
Park it or fix it my 02cents.
Orich
Park it or fix it my 02cents.
Orich
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
Brakes are something that should solidly react the instant you step on the pedal --no mushy, spongy feel or have to first be pumped before they will build up pressure.
Just for an example of perspective, let's imagine you're driving along on the highway at 60 MPH. Something suddenly happens in front of you that requires you be able to immediately haul the truck down from speed.
The chances of that happening with brakes that immediately respond to an input on the brake pedal would have the possibility for a good outcome.
If you have to take an extra second and a half to pump the brakes, just to begin to get a firm pedal, the extra second and a half required to do that might have been too long.
At 60 MPH, you are traveling at 88 feet per second. In one and a half seconds, you will have covered 132 feet.
Just for an example of perspective, let's imagine you're driving along on the highway at 60 MPH. Something suddenly happens in front of you that requires you be able to immediately haul the truck down from speed.
The chances of that happening with brakes that immediately respond to an input on the brake pedal would have the possibility for a good outcome.
If you have to take an extra second and a half to pump the brakes, just to begin to get a firm pedal, the extra second and a half required to do that might have been too long.
At 60 MPH, you are traveling at 88 feet per second. In one and a half seconds, you will have covered 132 feet.
Logistics Pro
Joined: Nov 2012
Posts: 4,308
Likes: 19
From: Las Vegas, NV
If you have to pump the brakes, they are either way out of adjustment or there is air in the system.
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Post Fiend
Joined: Jun 2003
Posts: 8,209
Likes: 12
From: Black Hills of SD
Yup, that. If the pedal is firm after you pump it up, I would adjust the brakes to see where that's at first, maybe something let go in one of the wheels and you lost some adjustment. If one (or more) wheel is way out of adjustment, better pull it apart and see what's going on. And yeah, ditch the used mc and buy a new one, they are cheap. The cloudy fluid could be a lot of things.
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