brakes
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New User
Joined: Jan 2002
Posts: 6
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brakes
Can anyone shed some light on my brake problem?
here is my problem : my brake pedal is hard, the truck stops,
however if i sit at a stop light for a lenght of time (20-30seconds) the pedal slowy starts to sink to the floor. I think it is either the master cylinder or perhaps the booster, however I would like to perhaps narrow it down before i start replaceing stuff I don't need to. Any insight would be greatly appreciated
here is my problem : my brake pedal is hard, the truck stops,
however if i sit at a stop light for a lenght of time (20-30seconds) the pedal slowy starts to sink to the floor. I think it is either the master cylinder or perhaps the booster, however I would like to perhaps narrow it down before i start replaceing stuff I don't need to. Any insight would be greatly appreciated
Senior User
Joined: Apr 2002
Posts: 406
Likes: 1
From: cedar rapids usa
brakes
Look for the wet spot.
I dought if its your booster. This work off of vacuum and if it didn't work you would need a LOT of force to power your brakes. If it had a leak you would be feeling the exact opisite, braked harder to hold the longer you sit.
Check your fuild and make sure its full. Have someone hold the break pedal and start at the master cylinder. Look for the wet spot. If it is the master cylinder the booster will usually have a brake fluid flim on it where the cylinder mounts to it. Next go down and check your front brakes. Follow the lines down the front. Look for either a leak or the flim build up described above but this time on your calipers.
Now on to the rear. Turn off the truck and get it on a level playing field. Secure it on jack stands and start tracing the brake lines from the cylinder to the rear. Keep looking for that wet spot or film of fluid and dust. If everything there is ok it's time to pull off the rear tires and drums and look over the rear wheel cylinders. Might be worth your time to put on new brake shoes while your down there. They are only 15 bucks and you got the drum off it anyways.
IF you can't find a leak and see no signs of a wet spot or brake fluid film and dust build up then I would gather that you have some air in the lines. Air is a gas and compresses under pressure. Has you hold the break the air is forced to the calipers and/or wheel cylinders. When it gets there the fluid pressure in the system is no longer working on pressing your brakes but is compressing the air. This is why you feel a strong pedal to start but falls off after time. So the answer is if no leaks bleed the brakes. There is only one way that I know of that air can get in the lines if there is not a leak and that is from a bad rubber seal under the brake cap so I would replace that if you do find you have air trapped in the lines.
Hope this helps ya.
I dought if its your booster. This work off of vacuum and if it didn't work you would need a LOT of force to power your brakes. If it had a leak you would be feeling the exact opisite, braked harder to hold the longer you sit.
Check your fuild and make sure its full. Have someone hold the break pedal and start at the master cylinder. Look for the wet spot. If it is the master cylinder the booster will usually have a brake fluid flim on it where the cylinder mounts to it. Next go down and check your front brakes. Follow the lines down the front. Look for either a leak or the flim build up described above but this time on your calipers.
Now on to the rear. Turn off the truck and get it on a level playing field. Secure it on jack stands and start tracing the brake lines from the cylinder to the rear. Keep looking for that wet spot or film of fluid and dust. If everything there is ok it's time to pull off the rear tires and drums and look over the rear wheel cylinders. Might be worth your time to put on new brake shoes while your down there. They are only 15 bucks and you got the drum off it anyways.
IF you can't find a leak and see no signs of a wet spot or brake fluid film and dust build up then I would gather that you have some air in the lines. Air is a gas and compresses under pressure. Has you hold the break the air is forced to the calipers and/or wheel cylinders. When it gets there the fluid pressure in the system is no longer working on pressing your brakes but is compressing the air. This is why you feel a strong pedal to start but falls off after time. So the answer is if no leaks bleed the brakes. There is only one way that I know of that air can get in the lines if there is not a leak and that is from a bad rubber seal under the brake cap so I would replace that if you do find you have air trapped in the lines.
Hope this helps ya.
Posting Guru
Joined: Jul 2001
Posts: 1,613
Likes: 2
From: Gainesville, FL
brakes
All,
When a pedal creeps to the floor and no visible fluid is leaking then this can only be an internal leak in the master cylinder.
When the pedal is rock hard and an obvious need for strength is required to stop the truck then a lack of vacuum to the booster is the problem or the booster membrane is torn in which case the truck should run badly during braking and you should be able to hear the vacuum leak during braking.
My Way is the Highway,
KingFisher
When a pedal creeps to the floor and no visible fluid is leaking then this can only be an internal leak in the master cylinder.
When the pedal is rock hard and an obvious need for strength is required to stop the truck then a lack of vacuum to the booster is the problem or the booster membrane is torn in which case the truck should run badly during braking and you should be able to hear the vacuum leak during braking.
My Way is the Highway,
KingFisher
