Curious about Bendix Brake Booster "pedal feel"

[Stanglover]

This is just something I'm curious about, more than concerned. Back in 2010, I swapped out the front manual drum brakes for the SSBC Kelsey-Hayes style 4 piston disc conversion kit. One reason I chose this kit was that it fitted the drum brake spindles and proved to be a very easy change. I did install new SS brake lines while it was all apart. I did not have a brake booster at that time and drove the car as manual discs for the next 5 years. Early in 2016, the motor had to be re-rebuilt (not going into that right now) so I took the opportunity to totally redo the engine bay including installing a Cardone reman Bendix brake booster. It came unpainted, thought that kind of strange, they can rebuild it, but can't spend 50 cents on some paint! Anyway, I got it installed with a new PB master cylinder. A major pita for sure as the s/column had to come out, but gave me the opportunity to do some other mods to the clutch linkage, bronze bushings, and other interior 'stuff'.

So, what I'm curious about is the "pedal feel" which is not like my daily driver. I got used to a hard pedal without a p/b, but I don't notice any real benefit with it either. I did do a vacuum test with the check valve in place and it held 15" Hg for 5 mins, but could not get higher vacuum for some reason. I do not know of any other way to test the booster. The brakes work well for what they are, so I'm wondering what sort of pedal feel others get, hard as a rock or kinda squishy like a modern car? Obviously, I'm talking about similar brakes, not a super modern upgrade. A few responses would be appreciated.

Here's a pic of the "new" Cardone reman booster.

 

[Don C]

Mine takes very little pedal pressure to apply the brakes. Getting the pushrod length adjusted is critical. The best way to test it with the unit in the car is to pump the brakes 3 or 4 times with the engine off and while holding the brake pedal down start the engine, the pedal should go down a half inch or more after the engine vacuum is applied. I would also see if the check valve holds vacuum.

 

[Stanglover]

Mine takes very little pedal pressure to apply the brakes. Getting the pushrod length adjusted is critical. The best way to test it with the unit in the car is to pump the brakes 3 or 4 times with the engine off and while holding the brake pedal down start the engine, the pedal should go down a half inch or more after the engine vacuum is applied. I would also see if the check valve holds vacuum.

Thanks Don, I'll try that suggestion. The check valve holds vacuum on the booster, not sure if I can remove it and check it separately.

When I set up the push rod, I used a small plug of plasticine as a "gauge" to set the free play clearance to about .015" as I recall.

Do you have factory brakes? i.e. single piston

 

[Stanglover]

@Don C, I just did the test you suggested. I would say the pedal only moved by a 1/4" at most.

Funny thing is, I have always wondered about the quality of Cardone reman parts. I had problems with a distributor I got as well.

OR, could it be in the so-called correct power brake m/c? That would be an easier change. I think it is a 15/16" bore, would have to check.

 

[Don C]

Yes, mine is stock. I got my rebuilt at NAPA several years ago, don't know who the rebuilder was.

I'm in agreement with you, I suspect the booster is bad, and I'm with you on being bare metal, seems strange.

 

[Stanglover]

Yes, mine is stock. I got my rebuilt at NAPA several years ago, don't know who the rebuilder was.

I'm in agreement with you, I suspect the booster is bad, and I'm with you on being bare metal, seems strange.

Thanks Don. You're confirming my suspicions all along. The problem is finding a good replacement Bendix booster that works, or maybe I'll rebuild it myself. Then there is the work of replacing it, not something I'm looking forward to again. Talk about procrastination, been putting this off for 4 years now!!! 

 

[Don C]

I was able to replace mine without dropping the steering column. I connected 2 or 3 extensions together to be able to reach the nuts. I think I had to use a wobbly (u-joint) socket on one of them.

 

[Stanglover]

I was able to replace mine without dropping the steering column. I connected 2 or 3 extensions together to be able to reach the nuts. I think I had to use a wobbly (u-joint) socket on one of them.

Yes, I don't think I'll have to totally drop the column this time around. The first time I had to drill out the lower mounting bolts on the mounting bracket and that meant removing the bracket. Still not looking forward to doing it, but if I have to, well, I have to. The next trick will be finding one  (that works) and having it shipped in if I can't find one in Canada.

Thanks for you input Don.

 

[Stanglover]

I've looked around on the good ol' net and have not found a reliable supplier or rebuilder for the 11" Bendix booster. I don't trust Cardone anymore, so would like to avoid them if possible. So far, all I have found is the 9" flat booster that is offered by many brake system companies and that is not what I want. Rock Auto offer a R&R service, but again not any good for me right now. If I have to change this thing, I'd rather do a straight swap out and in. So, if anyone has any leads, please let me know. 

Thanks,

 

[Bentworker]

Booster Dewey out of Portland Oregon might be an option for a rebuild.

Are you running Dot 5?

What type of hoses do you have and how old are they?

Maybe double check pushrod play and bleed the brakes?

 

[Stanglover]

Booster Dewey out of Portland Oregon might be an option for a rebuild.

Are you running Dot 5?

What type of hoses do you have and how old are they?

Maybe double check pushrod play and bleed the brakes?

Thanks I'll check Booster Dewey. And no, the issue is none of possibility's you mentioned. Actually, I'm leaning more to a possibly bad check valve as this issue has not changed  one way or the other since I put the booster on. Or of course as this was a reman, it was f'd up from the get-go. I guess I only have myself to blame now for not addressing this sooner, but in reality, the car stops as good as it did before I put the booster on, so I'm not worried about safety.  It just could be better and that's why I wondered what sort of pedal feel other have with there stockish disc brakes.

I appreciate your input.

 

[Stanglover]

Update; last night I was able to try the pedal 'feel' on my friends 71 M code Mach 1 with factory disc/drums. Before hand, I watched a video on how to test the booster. I had also removed a verified the check valve was good. I know I have 17-18 " Hg vacuum, so that's good too. So, comparing the amount of pedal 'drop' on start up after pumping the pedal 3-4 times, it was not much different to mine. I wasn't able to drive the car at that time, but  I'm leaning more to thinking that is is just the way it is. IF I am able to pick up another reman booster without having to return mine as a core, I'll swap it out. For now, I still have adequate brakes, just not like modern car's brakes. 

Thanks to all for you input,

 

[tony-muscle]

I have spent a lot of effort and $$ trying to make the car stop better. While it stops very well, I still need to press the pedal harder compared to a modern car. My daily driver is a Toyota 4Runner and it takes very little effort pressing the pedal. In the Mustang you still have to press hard. That's even after upgrading to Wilwood discs at the four corners, Wilwood master with adjusting valve, all new steel/rubber lines and new brake booster from Leed. My vacuum at idle is 11"-12" so I was told that's a problem. So I went through the effort of installing a vacuum pump and tank to maintain 19"-21" of vacuum for the booster. Still that didn't make a difference. My pedal "feel" today is the same as it was with the stock booster and I am now used to it. The braking is improved but the feel is the same.

I think that the main issue is that the booster is small compared to newer cars. The Leed booster is only 9" diameter and I think the stock was 10". An improvement would be to add a dual diaphragm, but then that will take more space.

 

[c9zx]

"I used a small plug of plasticine as a "gauge" to set the free play clearance to about .015" as I recall."  The ideal setting of the pushrod length is "exact contact" ie. no slack and no master cylinder piston movement. "The master cylinder piston should not move more than .015 inch as it contacts the pushrod." Adjusting it this way may not decrease pedal effort but should respond with less pedal travel. Chuck

 

[Omie01]

I have a re-man booster with stock calipers and slotted rotors, and my engine only has 15hg vacuum, stainless flexible brake lines and drums in back still. My pedal is stiff but by no means unusable. Just stiff. Cardone did my booster as well. Good luck!

 

[Stanglover]

"I used a small plug of plasticine as a "gauge" to set the free play clearance to about .015" as I recall."  The ideal setting of the pushrod length is "exact contact" ie. no slack and no master cylinder piston movement. "The master cylinder piston should not move more than .015 inch as it contacts the pushrod." Adjusting it this way may not decrease pedal effort but should respond with less pedal travel. Chuck

Chuck, I would have to check, but I'm sure the installation instructions describe setting the pushrod with .015" clearance. If not, then where did I get that from? If I have to remove the booster or m/c again, I'll look at that for sure.

Thanks.

Chuck, so you're right again! I checked my manual and it refers to using a "gauge" that nobody has of course, BUT it does say as an approximate adjustment only, a MAX of .015" movement on the m/c piston is acceptable. No movement (exact contact) is ideal. So, either the instruction with the booster or m/c I got where wrong, or I misunderstood them. 

 

[Stanglover]

I have spent a lot of effort and $$ trying to make the car stop better. While it stops very well, I still need to press the pedal harder compared to a modern car. My daily driver is a Toyota 4Runner and it takes very little effort pressing the pedal. In the Mustang you still have to press hard. That's even after upgrading to Wilwood discs at the four corners, Wilwood master with adjusting valve, all new steel/rubber lines and new brake booster from Leed. My vacuum at idle is 11"-12" so I was told that's a problem. So I went through the effort of installing a vacuum pump and tank to maintain 19"-21" of vacuum for the booster. Still that didn't make a difference. My pedal "feel" today is the same as it was with the stock booster and I am now used to it. The braking is improved but the feel is the same.

I think that the main issue is that the booster is small compared to newer cars. The Leed booster is only 9" diameter and I think the stock was 10". An improvement would be to add a dual diaphragm, but then that will take more space.

Thanks Tony,  From the replies I'm getting, I think you're right, it's  just the way it is. The braking is adequate and waaaay better than it was with manual drums, but as we're used to modern (electric) power brakes (VW) that will stop on a dime, maybe we're just expecting too much from ancient technology.

 

[Stanglover]

I have a re-man booster with stock calipers and slotted rotors, and my engine only has 15hg vacuum, stainless flexible brake lines and drums in back still. My pedal is stiff but by no means unusable. Just stiff. Cardone did my booster as well. Good luck!

Sounds like exactly the same as mine. It's good to know that others have pretty much the same "feel" so it's reassuring for sure.

Thanks for the reply.

 

[Stanglover]

Chuck, I would have to check, but I'm sure the installation instructions describe setting the pushrod with .015" clearance. If not, then where did I get that from? If I have to remove the booster or m/c again, I'll look at that for sure.

Thanks.

Chuck, so you're right again! I checked my manual and it refers to using a "gauge" that nobody has of course, BUT it does say as an approximate adjustment only, a MAX of .015" movement on the m/c piston is acceptable. No movement (exact contact) is ideal. So, either the instruction with the booster or m/c I got where wrong, or I misunderstood them. 

Chuck, Today, I pulled the m/c off, and as the lines were still attached, ( I did it the lazy way) I adjusted the contact nut a 1/2 turn forward, which I figure is close to .015", thread pitch appears to be about .030". I have not driven the car yet to test if any improvement. Good enough for now.

Thanks to all for your input.