Spongey pedal
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Cross-Country
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Spongey pedal
I bled the brakes on my 1988 f250 and the brakes are still spongey. is it safe to say that the problem is either with the ABS module or a vacuum leak on the master cylinder? If anyone has a good in-order checklist to narrow down where the problem is, that would be super helpful. Thanks!
Laughing Gas
Joined: Jan 2012
Posts: 1,106
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I fought the soft pedal for awhile, even installed a new master cylinder and rabs unit and ss brake line, still soft, tried adjusting the rod in the booster, still soft, finally got curious and replaced the booster with a new unit from Oreillys and the pedal was firm after that, so might check your booster.
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Cross-Country
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I fought the soft pedal for awhile, even installed a new master cylinder and rabs unit and ss brake line, still soft, tried adjusting the rod in the booster, still soft, finally got curious and replaced the booster with a new unit from Oreillys and the pedal was firm after that, so might check your booster.
Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
Now that you mention it, my old booster would hiss to, after searching and reading threads about a bad booster causing a hard pedal which is true, I think mine was leaking vacuum or something, but after replacing it my pedal went back to being firm. My breaks work decent but I wish I had a bit more stopping power as the front calipers are from a 79 f150/bronco when I did my SAS but still have a firm pedal.
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Cross-Country
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Now that you mention it, my old booster would hiss to, after searching and reading threads about a bad booster causing a hard pedal which is true, I think mine was leaking vacuum or something, but after replacing it my pedal went back to being firm. My breaks work decent but I wish I had a bit more stopping power as the front calipers are from a 79 f150/bronco when I did my SAS but still have a firm pedal.
Fleet Owner
Joined: Oct 2005
Posts: 20,789
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From: Kentucky
Before spending money on parts take a look at the rear wheel cylinders and the rear brake adjustment. If the rear adjusters are stuck then it takes a lot more brake pedal travel to engage the rear brake shoes. That can be interpreted as "spongy". If you notice the master cylinder gets low on fluid quickly then definitely take a look at the rear wheel cylinders. They can leak and not show any external signs for quite sometime in my experience.
Logistics Pro
Joined: Dec 2003
Posts: 3,779
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From: Foothills of NC
My master hisses when brakes applied. It's the shaft seal for the plunger worn. I also have somewhat spongy brakes from it, as several year ago I replaced all wheel cylinders and adjusters on the rear, and have also since changed front calipers and rubber hoses.
First, make sure the front rubber hoses to the calipers are not swelling when the brakes are applied, and do the same for the one at the rear axle. These hoses are all 30+ years old now. Pull rear brake drums and make sure the adjusters are free, and the self adjusters are working correctly. The sharp edge on the adjuster arm wears off on the self adjuster and will slip on the star wheel, especially as the adjusters get stiffer with age and corrosion.
If all that is good, I would say it's the brake booster. If it's hissing, it actually needs replacing anyway. Mine has hissed for quite a few years, but it's getting to the point now I need to replace it while they are still available.
First, make sure the front rubber hoses to the calipers are not swelling when the brakes are applied, and do the same for the one at the rear axle. These hoses are all 30+ years old now. Pull rear brake drums and make sure the adjusters are free, and the self adjusters are working correctly. The sharp edge on the adjuster arm wears off on the self adjuster and will slip on the star wheel, especially as the adjusters get stiffer with age and corrosion.
If all that is good, I would say it's the brake booster. If it's hissing, it actually needs replacing anyway. Mine has hissed for quite a few years, but it's getting to the point now I need to replace it while they are still available.
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Cross-Country
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Before spending money on parts take a look at the rear wheel cylinders and the rear brake adjustment. If the rear adjusters are stuck then it takes a lot more brake pedal travel to engage the rear brake shoes. That can be interpreted as "spongy". If you notice the master cylinder gets low on fluid quickly then definitely take a look at the rear wheel cylinders. They can leak and not show any external signs for quite sometime in my experience.
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Cross-Country
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My master hisses when brakes applied. It's the shaft seal for the plunger worn. I also have somewhat spongy brakes from it, as several year ago I replaced all wheel cylinders and adjusters on the rear, and have also since changed front calipers and rubber hoses.
First, make sure the front rubber hoses to the calipers are not swelling when the brakes are applied, and do the same for the one at the rear axle. These hoses are all 30+ years old now. Pull rear brake drums and make sure the adjusters are free, and the self adjusters are working correctly. The sharp edge on the adjuster arm wears off on the self adjuster and will slip on the star wheel, especially as the adjusters get stiffer with age and corrosion.
If all that is good, I would say it's the brake booster. If it's hissing, it actually needs replacing anyway. Mine has hissed for quite a few years, but it's getting to the point now I need to replace it while they are still available.
First, make sure the front rubber hoses to the calipers are not swelling when the brakes are applied, and do the same for the one at the rear axle. These hoses are all 30+ years old now. Pull rear brake drums and make sure the adjusters are free, and the self adjusters are working correctly. The sharp edge on the adjuster arm wears off on the self adjuster and will slip on the star wheel, especially as the adjusters get stiffer with age and corrosion.
If all that is good, I would say it's the brake booster. If it's hissing, it actually needs replacing anyway. Mine has hissed for quite a few years, but it's getting to the point now I need to replace it while they are still available.
Logistics Pro
Joined: Dec 2003
Posts: 3,779
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From: Foothills of NC
If the engine is running, and you have someone push the brake pedal rather hard, and old hose will physically swell so that you can feel it in your hand. This will cause spongy brakes. The hose will normally get harder when the brakes are applied, but shouldn't get bigger around.
I had to replace mine because the hoses were collapsing inside, causing fluid to enter the calipers, but not flow back, causing dragging and overheating. I thought I had another stuck caliper until I opened the bleed valve and was able to retract the pads. So, I replaced both front and have had no other problems on front.
They don't come off easy on these old trucks that have seen salt and corrosion. Took lots of penetrating oil and a good grip on the fittings to keep from twisting them off, but didn't take all that long. Just take your time if you do it and be careful not to twist or break the metal line.
I had to replace mine because the hoses were collapsing inside, causing fluid to enter the calipers, but not flow back, causing dragging and overheating. I thought I had another stuck caliper until I opened the bleed valve and was able to retract the pads. So, I replaced both front and have had no other problems on front.
They don't come off easy on these old trucks that have seen salt and corrosion. Took lots of penetrating oil and a good grip on the fittings to keep from twisting them off, but didn't take all that long. Just take your time if you do it and be careful not to twist or break the metal line.
Thread Starter
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Cross-Country
Joined: Jul 2019
Posts: 62
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If the engine is running, and you have someone push the brake pedal rather hard, and old hose will physically swell so that you can feel it in your hand. This will cause spongy brakes. The hose will normally get harder when the brakes are applied, but shouldn't get bigger around.
I had to replace mine because the hoses were collapsing inside, causing fluid to enter the calipers, but not flow back, causing dragging and overheating. I thought I had another stuck caliper until I opened the bleed valve and was able to retract the pads. So, I replaced both front and have had no other problems on front.
They don't come off easy on these old trucks that have seen salt and corrosion. Took lots of penetrating oil and a good grip on the fittings to keep from twisting them off, but didn't take all that long. Just take your time if you do it and be careful not to twist or break the metal line.
I had to replace mine because the hoses were collapsing inside, causing fluid to enter the calipers, but not flow back, causing dragging and overheating. I thought I had another stuck caliper until I opened the bleed valve and was able to retract the pads. So, I replaced both front and have had no other problems on front.
They don't come off easy on these old trucks that have seen salt and corrosion. Took lots of penetrating oil and a good grip on the fittings to keep from twisting them off, but didn't take all that long. Just take your time if you do it and be careful not to twist or break the metal line.
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