Brakes go to the floor...but still catch on??

oh dam

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Ok so whole back story last year i changed my front manual drums to wilwood 4p disc with a hydroboost. So this system worked flawlessly absolutely no issue, till now. About 2 months ago the pedal started to feel mushy and at a stop light it felt like it lost pressure since the car will suddenly start going forward resulting in me having to put more pressure. thinking it was just air i drive it around for another 100 or so miles. So i did some suspension work and thought might as well bleed the system so i can get on it :D ..except the pedal got worse :( . Before it didnt sink to the floor but after i bled it, went straight down and barely caught on. at some point i was going down hill i couldnt stop so i pushed it a little harder and my rear drums locked up, but not my front disc. So ok i thought bad master cylinder. Well, i put in the master cylinder, new lines from master cylinder to prop valve, and bench bled the master as well as bleed all 4 brakes. guess what..still having the same issue :exclamation: , but the brakes got a little less scary and better! yay! -_-.. So now that leaves me to the prop valve. did that go bad? how can i check? do i need to bleed it? it has never been changed. If it isnt the prop valve then the pedal might need adjustments, since it catches on but, late. if that makes sense. I am no mechanic or expert in brakes, any ideas guys?

 

midlife

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Old rubber brake hoses can expand giving you that sinking feeling. How old are they?

 

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Warped rotors or loose front wheels can cause the positions/pads to retract too far for a single pump of the pedal to be able to press the pads against the rotor.

 

phagan63

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I didn't notice in your post ... Do you still have drums on the back ? If you do make sure to check for leaking wheel cylinders back there. I had the same issue with my 67 F100 when I converted to front discs. I kept thinking I screwed up the installation somehow. After going through all the possible problems the front brakes might have had, I finally went to the back and inspected everything. Wound up being a bad wheel cylinder on one of the back drums.

 

oh dam

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Old rubber brake hoses can expand giving you that sinking feeling. How old are they?
the rear hoses were replaced with steel braided hoses about 5 years ago and the fronts when i changed my front brakes



Warped rotors or loose front wheels can cause the positions/pads to retract too far for a single pump of the pedal to be able to press the pads against the rotor.
Hmmm. I am pretty sure they arent warped (i hope not :s) i will have to check them out, but the wheels are one tight and torqued



I didn't notice in your post ... Do you still have drums on the back ? If you do make sure to check for leaking wheel cylinders back there. I had the same issue with my 67 F100 when I converted to front discs. I kept thinking I screwed up the installation somehow. After going through all the possible problems the front brakes might have had, I finally went to the back and inspected everything. Wound up being a bad wheel cylinder on one of the back drums.
I'm sorry if it wasnt clear, but yes still drums in the rear. Did the leaky wheel cylinders cause brake fluid to waste?

 
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goodnigh

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I didn't notice in your post ... Do you still have drums on the back ? If you do make sure to check for leaking wheel cylinders back there. I had the same issue with my 67 F100 when I converted to front discs. I kept thinking I screwed up the installation somehow. After going through all the possible problems the front brakes might have had, I finally went to the back and inspected everything. Wound up being a bad wheel cylinder on one of the back drums.
+1 on that. Had the same symptoms described in the original post

and it was a leaking rear wheel cylinder.

mike

 

phagan63

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Old rubber brake hoses can expand giving you that sinking feeling. How old are they?
the rear hoses were replaced with steel braided hoses about 5 years ago and the fronts when i changed my front brakes



Warped rotors or loose front wheels can cause the positions/pads to retract too far for a single pump of the pedal to be able to press the pads against the rotor.
Hmmm. I am pretty sure they arent warped (i hope not :s) i will have to check them out, but the wheels are one tight and torqued



I didn't notice in your post ... Do you still have drums on the back ? If you do make sure to check for leaking wheel cylinders back there. I had the same issue with my 67 F100 when I converted to front discs. I kept thinking I screwed up the installation somehow. After going through all the possible problems the front brakes might have had, I finally went to the back and inspected everything. Wound up being a bad wheel cylinder on one of the back drums.
I'm sorry if it wasnt clear, but yes still drums in the rear. Did the leaky wheel cylinders cause brake fluid to waste?
In my instance, yes it did because the fluid was leaking out of the cylinder. I didn't realize it until I actually crawled back there and looked and saw the back plate was a little damp. I think it's possible for them to leak internally without any obvious indication showing on the outside.

 

oh dam

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Old rubber brake hoses can expand giving you that sinking feeling. How old are they?
the rear hoses were replaced with steel braided hoses about 5 years ago and the fronts when i changed my front brakes



Warped rotors or loose front wheels can cause the positions/pads to retract too far for a single pump of the pedal to be able to press the pads against the rotor.
Hmmm. I am pretty sure they arent warped (i hope not :s) i will have to check them out, but the wheels are one tight and torqued



I didn't notice in your post ... Do you still have drums on the back ? If you do make sure to check for leaking wheel cylinders back there. I had the same issue with my 67 F100 when I converted to front discs. I kept thinking I screwed up the installation somehow. After going through all the possible problems the front brakes might have had, I finally went to the back and inspected everything. Wound up being a bad wheel cylinder on one of the back drums.
I'm sorry if it wasnt clear, but yes still drums in the rear. Did the leaky wheel cylinders cause brake fluid to waste?
In my instance, yes it did because the fluid was leaking out of the cylinder. I didn't realize it until I actually crawled back there and looked and saw the back plate was a little damp. I think it's possible for them to leak internally without any obvious indication showing on the outside.
what would be a way to check it? just remove it and inspect it?



I didn't notice in your post ... Do you still have drums on the back ? If you do make sure to check for leaking wheel cylinders back there. I had the same issue with my 67 F100 when I converted to front discs. I kept thinking I screwed up the installation somehow. After going through all the possible problems the front brakes might have had, I finally went to the back and inspected everything. Wound up being a bad wheel cylinder on one of the back drums.
+1 on that. Had the same symptoms described in the original post

and it was a leaking rear wheel cylinder.

mike
interesting. i think ill have to really check them out. This is scary and it sucks :/

 
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jbojo

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Ok so whole back story last year i changed my front manual drums to wilwood 4p disc with a hydroboost. So this system worked flawlessly absolutely no issue, till now. About 2 months ago the pedal started to feel mushy and at a stop light it felt like it lost pressure since the car will suddenly start going forward resulting in me having to put more pressure. thinking it was just air i drive it around for another 100 or so miles. So i did some suspension work and thought might as well bleed the system so i can get on it :D ..except the pedal got worse :( . Before it didnt sink to the floor but after i bled it, went straight down and barely caught on. at some point i was going down hill i couldnt stop so i pushed it a little harder and my rear drums locked up, but not my front disc. So ok i thought bad master cylinder. Well, i put in the master cylinder, new lines from master cylinder to prop valve, and bench bled the master as well as bleed all 4 brakes. guess what..still having the same issue :exclamation: , but the brakes got a little less scary and better! yay! -_-.. So now that leaves me to the prop valve. did that go bad? how can i check? do i need to bleed it? it has never been changed. If it isnt the prop valve then the pedal might need adjustments, since it catches on but, late. if that makes sense. I am no mechanic or expert in brakes, any ideas guys?
There are rubber seals in the proportioning valve that wear and cause them to stick. Before I replaced mine I was not getting the proper amount of fluid to the brakes so sloppy brakes, just throwing this out as a suggestion.

-jbojo

 

phagan63

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the rear hoses were replaced with steel braided hoses about 5 years ago and the fronts when i changed my front brakes



Hmmm. I am pretty sure they arent warped (i hope not :s) i will have to check them out, but the wheels are one tight and torqued



I'm sorry if it wasnt clear, but yes still drums in the rear. Did the leaky wheel cylinders cause brake fluid to waste?
In my instance, yes it did because the fluid was leaking out of the cylinder. I didn't realize it until I actually crawled back there and looked and saw the back plate was a little damp. I think it's possible for them to leak internally without any obvious indication showing on the outside.
what would be a way to check it? just remove it and inspect it?



I didn't notice in your post ... Do you still have drums on the back ? If you do make sure to check for leaking wheel cylinders back there. I had the same issue with my 67 F100 when I converted to front discs. I kept thinking I screwed up the installation somehow. After going through all the possible problems the front brakes might have had, I finally went to the back and inspected everything. Wound up being a bad wheel cylinder on one of the back drums.
+1 on that. Had the same symptoms described in the original post

and it was a leaking rear wheel cylinder.

mike
interesting. i think ill have to really check them out. This is scary and it sucks :/
"what would be a way to check it? just remove it and inspect it?"

I'd start with the easiest and move toward the more complex. Get up under the car and behind the rear wheels where you can see the the back plate of the drum assemblies and look for any signs of dampness. If you can't, pull the rear wheels off and look from that perspective. If it still looks dry I guess the next step is to pull the drums themselves off and inspect each wheel cylinder. After that ... I'm not sure because I found my problem before I got that far. Good luck to you. Hope it turns out to be something simple.


I was just thinking some more about your problem and a question came to my mind. You said you converted from front drum to front disc brakes. I'm sure the conversion was done correctly but sometimes little things slip past us. Did that conversion include a new proportioning valve ? I didn't read anywhere in your original post if you had changed out the original distribution block with the proper proportioning valve. If by chance you didn't, this could be the source of your problems. Just a thought.

 
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jbojo

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In my instance, yes it did because the fluid was leaking out of the cylinder. I didn't realize it until I actually crawled back there and looked and saw the back plate was a little damp. I think it's possible for them to leak internally without any obvious indication showing on the outside.
what would be a way to check it? just remove it and inspect it?



+1 on that. Had the same symptoms described in the original post

and it was a leaking rear wheel cylinder.

mike
interesting. i think ill have to really check them out. This is scary and it sucks :/
"what would be a way to check it? just remove it and inspect it?"

I'd start with the easiest and move toward the more complex. Get up under the car and behind the rear wheels where you can see the the back plate of the drum assemblies and look for any signs of dampness. If you can't, pull the rear wheels off and look from that perspective. If it still looks dry I guess the next step is to pull the drums themselves off and inspect each wheel cylinder. After that ... I'm not sure because I found my problem before I got that far. Good luck to you. Hope it turns out to be something simple.


I was just thinking some more about your problem and a question came to my mind. You said you converted from front drum to front disc brakes. I'm sure the conversion was done correctly but sometimes little things slip past us. Did that conversion include a new proportioning valve ? I didn't read anywhere in your original post if you had changed out the original distribution block with the proper proportioning valve. If by chance you didn't, this could be the source of your problems. Just a thought.
Travis (aka Doug the dog) pointed me to a place where you could get the Disc to Disc proportioning valve.

https://secure19.hostek.net/mustangbrakeparts-com/proddetail.asp?prod=1365

Works just fine.

-jbojo

 

oh dam

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"I was just thinking some more about your problem and a question came to my mind. You said you converted from front drum to front disc brakes. I'm sure the conversion was done correctly but sometimes little things slip past us. Did that conversion include a new proportioning valve ? I didn't read anywhere in your original post if you had changed out the original distribution block with the proper proportioning valve. If by chance you didn't, this could be the source of your problems. Just a thought."

the conversion did not include a proportional valve. but i was running the factory drum all around prop valve with no problem. The problems started happening after i changed brake fluids. So that might be the problem.

 

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­FYI

The three main types of brake fluid now available are DOT3, DOT4 and DOT5. DOT3 and DOT4 are glycol-based fluids, and DOT5 is silicon-based. The main difference is that DOT3 and DOT4 absorb water, while DOT5 doesn't.

One of the important characteristics of brake fluid is its boiling point. Hydraulic systems rely on an incompressible fluid to transmit force. Liquids are generally incompressible while gases are compressible. If the brake fluid boils (becomes a gas), it will lose most of its ability to transmit force. This may partially or completely disable the brakes. To make matters worse, the only time you are likely to boil your brake fluid is during a period of prolonged braking, such a drive down a mountain -- certainly not the best time for brake failure!

­As a DOT3 or DOT4 brake fluid absorbs water, its boiling point decreases. It can absorb water from the air, which is why you should avoid opening your car's brake fluid reservoir. For the same reason, you should always keep containers of brake fluid tightly sealed.

DOT5 fluid does not absorb water. This means the boiling point will remain relatively stable, but it also means that any water that does get into your brake system will tend to form pure water pockets, which could cause brake corrosion.

Two other important things about brake fluid: DOT3 and DOT4 eat paint, so don't spill either of these on your car. Also, none of the different types of brake fluid should be mixed. They can react badly with each other and corrode your brake system.

 

phagan63

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"I was just thinking some more about your problem and a question came to my mind. You said you converted from front drum to front disc brakes. I'm sure the conversion was done correctly but sometimes little things slip past us. Did that conversion include a new proportioning valve ? I didn't read anywhere in your original post if you had changed out the original distribution block with the proper proportioning valve. If by chance you didn't, this could be the source of your problems. Just a thought."

the conversion did not include a proportional valve. but i was running the factory drum all around prop valve with no problem. The problems started happening after i changed brake fluids. So that might be the problem.
I'm certainly no expert on these things but just about every article I've read concerning drum to disc conversions, and I've read a bunch because I did the conversion on my 67 F100 a few years ago, advises installing the proper proportioning valve for front disc/rear drum applications. Some articles state that you can keep the original distribution block but should add an adjustable proportioning valve for the rear brakes. I just went ahead and removed the original block and installed the appropriate proportioning valve. This may not be the source of your current problem but in my humble opinion, it's probably something you should consider in the near future.

I'm not sure what dangers might exist, if any, by not having that specific component. Maybe some of the other more experienced forum members might have some thoughts on this.

 
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JimNiki

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The guy is saying that the setup as it is worked fine for a while.

Unless the prop valve has gone bad in the last 2 months?

Can we confirm 100‰ that the fluid in the reservoir is going down.

Let's answer that simple q first.

Maybe with the added pressure of better brakes, the booster is leaking either internally or at the firewall.

 
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cudak888

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Jack the back up, support it, remove the wheels, and pull the drums. Inspect cylinders while having a friend stomp on the pedal. Look for leaks.

If no leaks, move to one of the other suggestions. Might as well get the easiest diagnostics out of the way.

-Kurt

 

goodnigh

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The guy is saying that the setup as it is worked fine for a while.

Unless the prop valve has gone bad in the last 2 months?

Can we confirm 100‰ that the fluid in the reservoir is going down.

Let's answer that simple q first.

Maybe with the added pressure of better brakes, the booster is leaking either internally at the firewall.
+1 on that observation.

Besides a potential leak in a rear brake drum,

there could also be a leak in the booster.

Good call.

mike

 

oh dam

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The guy is saying that the setup as it is worked fine for a while.

Unless the prop valve has gone bad in the last 2 months?

Can we confirm 100‰ that the fluid in the reservoir is going down.

Let's answer that simple q first.

Maybe with the added pressure of better brakes, the booster is leaking either internally at the firewall.
confirm 100% fluid is not going down. Hydroboost is a "new" rebuilt component, so not likely it is leaking since there is no visible leaks and my power steering fluid isnt low.



­FYI

The three main types of brake fluid now available are DOT3, DOT4 and DOT5. DOT3 and DOT4 are glycol-based fluids, and DOT5 is silicon-based. The main difference is that DOT3 and DOT4 absorb water, while DOT5 doesn't.

One of the important characteristics of brake fluid is its boiling point. Hydraulic systems rely on an incompressible fluid to transmit force. Liquids are generally incompressible while gases are compressible. If the brake fluid boils (becomes a gas), it will lose most of its ability to transmit force. This may partially or completely disable the brakes. To make matters worse, the only time you are likely to boil your brake fluid is during a period of prolonged braking, such a drive down a mountain -- certainly not the best time for brake failure!

­As a DOT3 or DOT4 brake fluid absorbs water, its boiling point decreases. It can absorb water from the air, which is why you should avoid opening your car's brake fluid reservoir. For the same reason, you should always keep containers of brake fluid tightly sealed.

DOT5 fluid does not absorb water. This means the boiling point will remain relatively stable, but it also means that any water that does get into your brake system will tend to form pure water pockets, which could cause brake corrosion.

Two other important things about brake fluid: DOT3 and DOT4 eat paint, so don't spill either of these on your car. Also, none of the different types of brake fluid should be mixed. They can react badly with each other and corrode your brake system.
how can i know if my brakes are corroded? i really hope not, my wilwood are barely 1 year old..



"I was just thinking some more about your problem and a question came to my mind. You said you converted from front drum to front disc brakes. I'm sure the conversion was done correctly but sometimes little things slip past us. Did that conversion include a new proportioning valve ? I didn't read anywhere in your original post if you had changed out the original distribution block with the proper proportioning valve. If by chance you didn't, this could be the source of your problems. Just a thought."

the conversion did not include a proportional valve. but i was running the factory drum all around prop valve with no problem. The problems started happening after i changed brake fluids. So that might be the problem.
I'm certainly no expert on these things but just about every article I've read concerning drum to disc conversions, and I've read a bunch because I did the conversion on my 67 F100 a few years ago, advises installing the proper proportioning valve for front disc/rear drum applications. Some articles state that you can keep the original distribution block but should add an adjustable proportioning valve for the rear brakes. I just went ahead and removed the original block and installed the appropriate proportioning valve. This may not be the source of your current problem but in my humble opinion, it's probably something you should consider in the near future.

I'm not sure what dangers might exist, if any, by not having that specific component. Maybe some of the other more experienced forum members might have some thoughts on this.
I am going to change the Prop valve sooner or later, to the adjustable since i am going to do a rear disc conversion as well



Jack the back up, support it, remove the wheels, and pull the drums. Inspect cylinders while having a friend stomp on the pedal. Look for leaks.

If no leaks, move to one of the other suggestions. Might as well get the easiest diagnostics out of the way.

-Kurt
me and a friend removed the wheels to bleed the brakes and adjusted the drums as well, no leaks on either side.



The guy is saying that the setup as it is worked fine for a while.

Unless the prop valve has gone bad in the last 2 months?

Can we confirm 100‰ that the fluid in the reservoir is going down.

Let's answer that simple q first.

Maybe with the added pressure of better brakes, the booster is leaking either internally at the firewall.
+1 on that observation.

Besides a potential leak in a rear brake drum,

there could also be a leak in the booster.

Good call.

mike
would a leak in the hydrobooster cause this problem?

 
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JimNiki

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If there's enough pressure to lockup the rears, then logic tells me that the mc is working properly?

I spent half an hour years ago bleeding brakes with 2 people and still weren't happy with the feel.

Took it to a garage and they did it and said there was still plenty of air trapped in the lines.?

At this stage it is a bad prop valve, kinked brake lines to the front or air in the system. Anything else would cause a leak?

 
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