Another break problem

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Dec 13, 2006 | 02:04 PM

dieselbogging

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Senior User

Joined: Jul 2006

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From: Sandy Lake, MB

Another break problem

Just recently i started having trouble breaking. The pedal is getting stiff.The pedal goes to the floor. If i pump it, it will build pressure but it loses it after a minute. If i just hold the pedal, it slowly sinks to the floor. It is hard in the morning or when it is cold but when everything is warmed up it gets better but still not 100%.
I tested my vacuum pump and it is putting out about 16 psi instantly but takes about 20 seconds to hit 20 psi. It will not go any higher. Not only that, it is chirping.
I bled my breaks not too long ago but it only helped a bit. The break light will come on once in a while and will go off. Sometimes it comes on very lightly and flickers a bit.
Is my vacuum pump putting out enough? What could possibly be the problem?
On a previous post someone said that the pedal is supposed to slowly sink to the floor if you hold it while another guy said that this is not supposed to happen and said that the master cylinder must be replaced. Who's right?
Thanks in advance.

Last edited by dieselbogging; Dec 13, 2006 at 02:06 PM.

Dec 13, 2006 | 02:11 PM

Bigles

Junior User

Joined: Nov 2003

Posts: 98

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From: Talladega, AL.

Usualy when one slowly goes to the floor it is the master cylinder. If your pedal is hard and takes a lot of pressure to apply, I would say vacuum pump. Check the vacuum pressure on the booster line.

Dec 13, 2006 | 02:22 PM

xjvince

Mountain Pass

Joined: Jan 2006

Posts: 162

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From: oregon

I agree with bigles, exactly . also check under your truck for leaks at each wheel and the lines back to the MC. the light comes on when there is a unbalance in hydralic pressure front to rear due to a faulty MC ( the plunger in them has seperate front rear chambers) or a leak down line.

Dec 13, 2006 | 04:37 PM

dieselbogging

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From: Sandy Lake, MB

I checked the the pressure on the booster line and it was the same. I just popped it off and hooked the tester up. There are no air leaks or brake fluid leaks anywhere. I have a spare master cylinder and vacuum booster. How else would i test the master cylinder and vacuum booster?

Dec 13, 2006 | 05:04 PM

Ben-jamin

Tuned

Joined: Dec 2006

Posts: 291

Likes: 4

From: houston,tx

with your vacuum testor conected between the booster and line press on the brake and see how much it drops, if any; it should recover immediatly. or run the truck a couple of minutes and turn off; the booster should hold vacuum on its own until the brake is depressed providing that the check valve is good. to check master cylinder- disconnect the brake lines and find appropriate plugs to put back in the cylinder. now press the brake, if the pedal still creeps down the cylinder is bad

Dec 13, 2006 | 06:30 PM

dieselbogging

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From: Sandy Lake, MB

It does not hold vacuum when i turn the truck off. Ill try your test tomorrow. Thanks

Dec 13, 2006 | 09:54 PM

roamer37

Senior User

Joined: Dec 2003

Posts: 221

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From: Grosse Ile Mi.

You have a internal leak in your master cylinder.. one side to the other no fluid is leaking out.. Change it... you also have a frozen caliper on the passenger side.. all the pressure is going to the other side also change it then bleed all four wheels and bleed the master on the bench.. befor you install it..have someone push slowly down on the pedal after its all bolted while you hold your fingers over the ports till all the way down.While the pedel is down put the brake lines on.. then let the pedal up and do a full bleed to the system...make sure you dont run out of brake fluid while you are bleeding...