low brake pedal

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Feb 6, 2008 | 08:20 PM

tonfro

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low brake pedal

hello all
have a 82 f150 4.9 c6 with power brakes
have always had a low brake pedal, by that, i mean the pedal goes more than half way to the floor. lately the pedal was going almost to the floor. checked the master cylinder and the smaller resevoir was empty. figured a brake line was rusted out or the rear slave cylinders were leaking. got under truck and saw no signs of any fluid leaks. topped off master cylinder and drove it for a couple of days and then it start running rough at idle. it stalled out a few times getting home. checked brake fluid and it was empty again at the small resevoir but this time the fluid bubbled all the paint on the power booster. didnt have time to check anything when i got home, but seems to me the mc is leaking into the power booster. WILL NOT DRIVE TILL REPAIRED. does that make sense.
thanks
gt

Feb 6, 2008 | 08:28 PM

Rogue_Wulff

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From: Lost

Definately sounds like a bad MC. Low brake pedal could be the result of rear brakes out of adjustment.

Feb 6, 2008 | 08:36 PM

doug1222556

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It's possible, though I've never run into it. Low pedal usually means worn out shoes and drums and /or worn out calipers and rotors. Sounds like it's time for a new master, but you may need drums, shoes and rear wheel cylinders to go with it. The self adjusters are a good guage on the rear wheels as to where you are at, if you have a lot of pad material and they are opened up half-way, well , that's not good. You can kinda guage the rotors as well, the whole set-up, (pads and rotor) should just about fill the space in the caliper, (with new pads).

Feb 6, 2008 | 08:52 PM

kermmydog

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From: Western Central NV

I agree with it is time to do a complete brake job. Just fixing part of it isn't the best way to go.

Feb 6, 2008 | 08:53 PM

Holmesuser01

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From: Asheville, NC

Quote:

Originally Posted by tonfro

You need a master cylinder. You were wise to stop driving it. If you had continued topping off the cylinder, you'd be replacing the vacuum booster, too!

Feb 6, 2008 | 09:10 PM

ctubutis

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From: Denver Metro Area, CO

Quote:

Originally Posted by tonfro

topped off master cylinder and drove it for a couple of days and then it start running rough at idle. it stalled out a few times getting home. checked brake fluid and it was empty again at the small resevoir but this time the fluid bubbled all the paint on the power booster. didnt have time to check anything when i got home, but seems to me the mc is leaking into the power booster. WILL NOT DRIVE TILL REPAIRED. does that make sense.

I had purchased a rebuilt master cylinder but returned it and exchanged for a brand new one cuz it was leaking out the back. In my case, the fluid was dripping between the MC & booster junction, I discovered it while bleeding the system. Given your experience, it wouldn't surprise me if yours was leaking similarly only the fluid was getting sucked into the engine through the vacuum booster (causing your idling issues). Can't say for certain this is your problem but it wouldn't surprise me if it was so....

-chris
colorado, usa