poor braking and vacuum test
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Freshman User
Joined: Nov 2005
Posts: 29
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poor braking and vacuum test
Hi,
My brakes have been poor for awhile now and I've been doing a lot of work on the front ones lately. New pads, cylanders, rotors. The pedal is still not as firm as I would like it to be and there is too much pedal travel before I really start braking.
While I was at it I wanted to check the vacuum pump. My reason being that I had to adjust my vrv to get my tranny to start shifting properly. Could my poor braking be a sign of a failing vacuum pump diaghram or would it be harder to push on the pedal instead of softer if this was the problem?
I noticed that the test calls for a vacuum gauge. Could I use my mighty vac vacuum pump for this? Also is it better to T into the line off the vacuum pump or can I just unplug it from the brake booster and stick the gauge on. Also, how would I check the brake booster itself?
this is for the 87.
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87 F250 6.9 daily driver, xcab, 4x4
gathering parts for wvo conversion.
86 f250 6.9, xcab, 4x4, plow
My brakes have been poor for awhile now and I've been doing a lot of work on the front ones lately. New pads, cylanders, rotors. The pedal is still not as firm as I would like it to be and there is too much pedal travel before I really start braking.
While I was at it I wanted to check the vacuum pump. My reason being that I had to adjust my vrv to get my tranny to start shifting properly. Could my poor braking be a sign of a failing vacuum pump diaghram or would it be harder to push on the pedal instead of softer if this was the problem?
I noticed that the test calls for a vacuum gauge. Could I use my mighty vac vacuum pump for this? Also is it better to T into the line off the vacuum pump or can I just unplug it from the brake booster and stick the gauge on. Also, how would I check the brake booster itself?
this is for the 87.
--------------------
87 F250 6.9 daily driver, xcab, 4x4
gathering parts for wvo conversion.
86 f250 6.9, xcab, 4x4, plow
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
Vacuum makes it easier to depress the pedal. Soft pedal means something in the system is moving alot when you press the pedal. Obvious item would be the rubber brake lines going to each wheel cylinder or caliper. If the rears are not functing properly it will not matter what you do to the fronts. It's a system, all must be functioning for it to be right.
Sence you have replaced the calipers, inspect the wheel cylinders for leaks, broken linkage or excessive movement in the drums. Inspect the rubber brakelines for buldges. Replace the brake fluid, it absorbs water and compresses slightly easier than brake fluid. After all that, it's time to shop to for a master cylinder.
Sence you have replaced the calipers, inspect the wheel cylinders for leaks, broken linkage or excessive movement in the drums. Inspect the rubber brakelines for buldges. Replace the brake fluid, it absorbs water and compresses slightly easier than brake fluid. After all that, it's time to shop to for a master cylinder.
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
> The pedal is still not as firm as I would like it to be
Have you bleed the system using two people or only a brake bleeder? My experience has been brake bleeders (the cheap ones) let in a small amount of air and you never get the pedal you do when doing a two person bleed.
Have you bleed the system using two people or only a brake bleeder? My experience has been brake bleeders (the cheap ones) let in a small amount of air and you never get the pedal you do when doing a two person bleed.
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
> I may have backed the rears off too much when adjusting them
> there is too much pedal travel before I really start braking
Entirely possible, I have done it a few times myself and redid them after a road test when it felt like the vehicle was gliding instead of stopping..
Being a diesel, I would check the vacuum pump, but, it sounds like a soft pedal and not a hard pedal giving you problems so I do not think that or the booster is the problem. It might be the mstr cyl, but, I doubt it.
What has worked for a few is doing a gravity bleed, loosen the bleeders, jack the vehicle up (front or rear depending on which end was loosen) and leave it overnight. Then do a quick bleed while up in the air.
> there is too much pedal travel before I really start braking
Entirely possible, I have done it a few times myself and redid them after a road test when it felt like the vehicle was gliding instead of stopping..
Being a diesel, I would check the vacuum pump, but, it sounds like a soft pedal and not a hard pedal giving you problems so I do not think that or the booster is the problem. It might be the mstr cyl, but, I doubt it.
What has worked for a few is doing a gravity bleed, loosen the bleeders, jack the vehicle up (front or rear depending on which end was loosen) and leave it overnight. Then do a quick bleed while up in the air.
