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71 Bendix Master Brake Cylinder Meltdown

MoparGuy68

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I’ve got a Master Cylinder leak that has made my Bendix Brake Booster look like the face of “The Incredible Melting Man”.

You can scroll down to the next to last paragraph if you just want to see my question and don’t wanna read any boring history of my car.

There was already visible damage to the booster when I bought this car, but the leak seemed to be inactive. I had the rear wheels cylinders replaced, and a brake system flush at a Brake Masters in April. They pressed my brake pedal so many times, they nearly killed my battery while they “bled” the brakes. Ever since, I’ve had break fluid leaking daily from the master cylinder.

To protect my inner fender and frame rail, from further damage. I have wired a small aluminum pan under the booster to catch the leaking fluid. Most of the damage was already done over the previous owner’s watch, as he chose to do nothing about it. Like I have said before this car was neglected.

As some of you may already know, I’ve been fixing problems with this car continuously since I’ve owned it. Other problems were a higher priority over the brake cylinder. The aluminum pan was meant as a stop gap until the excessive heat in the Southwest passes.

I thought I’d give a little explanation as to why the brake booster and master cylinder look so horrific, but hopefully not too much to bore you.

The car appears to have a vintage Bendix booster, which I’m hoping can be saved. The master cylinder appears to be an aftermarket piece and not a vintage Bendix unit. The cylinder casting has “made in USA” cast into the bottom of it. This cylinder seems to be the correct style for 1971, just not a real Bendix cylinder.

I am asking for suggestions of what brand replacement cylinder to get just to attempt to stop the leakage and further deterioration of the brake booster. At some point in the future, if I ever transform this car into what I consider a “driveable vehicle”, I may try to get the correct vintage rebuilt Bendix cylinder. But for now, I’m thinking of trying to get a replacement remanufactured or new cylinder that’s not a piece of ****.

Definitely have leakage from the lid rubber seal. I think I also have piston seal leakage. Fluid level drops in the rear section (for the disc brakes), while the front section (for the drums) stays at the correct level. While driving the car, brakes feel normal. I always find some fluid in the aluminum catch pan after the car has sat motionless for a day.

0ABB36BD-765D-4EA3-9086-9D6821FB38CB.jpeg ABC35AEB-23AF-484F-B028-3EC4397874FD.jpeg 866B0974-F425-496F-AA04-220F2C4A238D.jpeg 54938543-A48F-4492-A8B1-154B14D2F436.jpeg 80496BC8-8CB0-4349-BD7C-313C321E669C.jpeg E278E77D-2E3A-4CF6-9C08-67B61DFE2C79.jpeg
 
About $40.oo on rock auto. And clean off the booster and paint it, if it still functions ok.
 
About $40.oo on rock auto. And clean off the booster and paint it, if it still functions ok.
I looked them up on Rockauto. I’ve also looked them up at Napa and O’Reillys. Most likely, all of these cylinders are newly manufactured in China.. May be ok to use temporarily. Maybe..
 
My research shows that 1971 cars, with powers disc brakes, came from the factory with either a Bendix or Midland Ross booster and cylinder. The Bendix booster was painted black, like mine is. The Midland Ross booster was cadmium plated. The Bendix booster was a carry over from the 1970 model year.

My car probably came with the Bendix, as it was built in early September of 70. My booster has part #18268, which appears to be correct for a non-Hemi car.
 
I’ve decided to send my master cylinder, booster, wheel cylinders and calipers out for restoration. They are going to Karp’s Power Brake in CA.

Removed the master cylinder and booster today. My “made in USA” wheels cylinders were already ready to go.

The rear piston on my cylinder really did a number on the booster. At least the booster shielded the firewall from the brake fluid.

I’m having a problem removing the passenger side caliper.. Will be asking for help on that in another thread.

42B4BC9D-8E52-4008-BF96-9979BC4C59BA.jpeg AFAB3243-7DA2-4069-8B8F-14ED40CAE045.jpeg
 
My research shows that 1971 cars, with powers disc brakes, came from the factory with either a Bendix or Midland Ross booster and cylinder. The Bendix booster was painted black, like mine is. The Midland Ross booster was cadmium plated. The Bendix booster was a carry over from the 1970 model year.

My car probably came with the Bendix, as it was built in early September of 70. My booster has part #18268, which appears to be correct for a non-Hemi car.
Learned something new today on the Bendix Booster for 1971 Non-Hemi

Interesting

Would that part # show on the Broadcast Sheet
 
I looked them up on Rockauto. I’ve also looked them up at Napa and O’Reillys. Most likely, all of these cylinders are newly manufactured in China.. May be ok to use temporarily. Maybe..


I'd take the new one over that rusty leaker you have now
Sending them all for a "rebuild" is good. Karps is a couple miles from me.
 
A shop bled your brakes by pressing the pedal? Even I use a simple power bleeder
 
Hope you have the master and wheel cylinders sleeved with brass or stainless steel.
 
Learned something new today on the Bendix Booster for 1971 Non-Hemi

Interesting

Would that part # show on the Broadcast Sheet
Can’t answer your question about the broadcast sheet. My car left the factory without it. The part #18268, that I posted above, is a Chrysler number. Part #10931 is the Bendix number on my booster.

I’ve been looking at other 71 Chargers with Bendix boosters. Looks like I’ll be having my booster and master cylinder powder coated black. With the cover and bail zinc plated in gold. Like the cars in the attached photos have.

0BBF6B38-54F1-432E-9891-29A8C2ECC0C4.jpeg 059A4DA3-BF54-4AD8-BFAB-1683657548E9.jpeg
 
Hope you have the master and wheel cylinders sleeved with brass or stainless steel.
They will sleeve with stainless steel if needed.. This is probably going to cost me 10x as much if I bought new made in Asia parts. I don’t want to have to do all this again in 6 months from now, so I’m dropping the extra money into the Super Bee bottomless money pit. I hope this car is worth it..
 
A shop bled your brakes by pressing the pedal? Even I use a simple power bleeder
Yep, and let the brake fluid shoot out all over my rear end and leaf springs. That was their “professional technique”. I questioned the guy, asking him why he wasn’t attaching a flexible tube to carry the fluid away from the car. His response was, “There are many ways to bleed brakes and this is one of them”. He muttered about how brake fluid is water soluble, and proceeded to spray some pressurized cleanser on my rear end and leaf springs, to attempt to wash off the brake fluid.

I’ll never take the car there again, and that Is why I’m doing this work myself. Even though I’ve never done most of it before.. Every penny I spent at that shop was completely wasted.

Don’t know what a power bleeder is. When it comes time for me to bleed the brakes, I’ll have to use some method that allows me to do it by myself.. Whatever that is, it won’t involve shooting brake fluid all over my rear end and leaf springs I tell you that.
 
I can't recommend trying to coat a brake booster. There are seals / diaphrams inside that will not survive the heat of the cure let alone outgassing temps.
 
I can't recommend trying to coat a brake booster. There are seals / diaphrams inside that will not survive the heat of the cure let alone outgassing temps.


You plate/coat the booster after it's disassembled not assembled. Karps should offer that service while it's being rebuilt
 
Yep, and let the brake fluid shoot out all over my rear end and leaf springs. That was their “professional technique”. I questioned the guy, asking him why he wasn’t attaching a flexible tube to carry the fluid away from the car. His response was, “There are many ways to bleed brakes and this is one of them”. He muttered about how brake fluid is water soluble, and proceeded to spray some pressurized cleanser on my rear end and leaf springs, to attempt to wash off the brake fluid.

I’ll never take the car there again, and that Is why I’m doing this work myself. Even though I’ve never done most of it before.. Every penny I spent at that shop was completely wasted.

Don’t know what a power bleeder is. When it comes time for me to bleed the brakes, I’ll have to use some method that allows me to do it by myself.. Whatever that is, it won’t involve shooting brake fluid all over my rear end and leaf springs I tell you that.


Use a power siphon unit. Low cost at HF, about $32. You do need a home air compressor. The bleeder is a gun that sucks the fluid at each wheel.
Brake Fluid Bleeder (harborfreight.com)
There are other types that are same function.
 
I used this to bleed new brakes and drain diff last weekend on my 70 RR. A little pricey but used it to get tranny fluid out of my pickup too -- I thought two different shops had done a flush on my tranny after repair work on pickup and this thing allowed me to realize how little they took out. Anyway, wanted to share it!
https://www.amazon.com/dp/B0836GH3G7
 
Drama continues on with my Bendix booster. Karps has had it for 3 months. This is the current hold up in getting it back to me.

The plastic hub inside the booster was cracked open. I did not know this when I sent the booster to them. The “new” replacement reproduction hub has a larger inside diameter than the old cracked hub.

Jeff, at Karps, is trying to locate the correct inside diameter hub, in his stash, to match the piston that was inside the old hub. If he cannot do that, he said he would have to put a larger diameter piston to match the larger bore in the repro hub. He said it’s his knowledge that this hub bore and piston are sized for certain car models, as in they could vary for the different car models. So he would prefer to use my old piston with a properly sized hub for it.

My 71 Charger has the B51 Power Brake code on the fender tag, but there is no B41 Disc Brake code. I am wondering if my car originally had a power booster with drum brakes all around. And at sometime in the past was converted to disc brakes in the front. Perhaps the inside hub and piston diameter is smaller for a drum Booster and larger for a disc Booster?

If that is the case then maybe he should use the new larger inside diameter hub with a larger piston to match up with it?

So the big Question... Do you guys know if Boosters used with Disc brakes used a larger hub piston than Boosters used with drum brakes?

You have to be a detective when dealing with cars that you don’t know all the history about.
 
Drama continues on with my Bendix booster. Karps has had it for 3 months. This is the current hold up in getting it back to me.

The plastic hub inside the booster was cracked open. I did not know this when I sent the booster to them. The “new” replacement reproduction hub has a larger inside diameter than the old cracked hub.

Jeff, at Karps, is trying to locate the correct inside diameter hub, in his stash, to match the piston that was inside the old hub. If he cannot do that, he said he would have to put a larger diameter piston to match the larger bore in the repro hub. He said it’s his knowledge that this hub bore and piston are sized for certain car models, as in they could vary for the different car models. So he would prefer to use my old piston with a properly sized hub for it.

My 71 Charger has the B51 Power Brake code on the fender tag, but there is no B41 Disc Brake code. I am wondering if my car originally had a power booster with drum brakes all around. And at sometime in the past was converted to disc brakes in the front. Perhaps the inside hub and piston diameter is smaller for a drum Booster and larger for a disc Booster?

If that is the case then maybe he should use the new larger inside diameter hub with a larger piston to match up with it?

So the big Question... Do you guys know if Boosters used with Disc brakes used a larger hub piston than Boosters used with drum brakes?

You have to be a detective when dealing with cars that you don’t know all the history about.


You should ask Karps this. And ask what difference does either one make as far as booster assist
 
You should ask Karps this. And ask what difference does either one make as far as booster assist
I just talked to Jeff at Karps today. He does not know what should be on my specific car, booster wise. He is just trying to match a hub with the piston that was in my booster when I sent it to him.

He also was unfamiliar with the caliper pin “positioners”. I had to send him service manual photos so he understood what I was talking about regarding pin positioners. He apparently doesn’t have vast knowledge about the details of 1968 to 1971 Mopar brakes. He’s not like the RAM MAN, who seems to be more knowledgeable on the brake systems used on old Mopars and all the details of the different model years.

A local Mopar restorer in my area recommend using Karps, that’s why I sent him my parts.

Tomorrow, when I talk to Jeff again, I will ask him if he knows what difference the different piston sizes make in operation.
 
Here's my 71 Charger that originally came with power disc, this car has sat for over 15 years so, this could be the original booster or an old replacement from back in the day but once I stripped the old paint off the booster it was gold anodized so I tried to match it with gold paint as close as I could goin by pics of original and restored cars online still may not be right though. Any help?? Tryin to contribute something is all...not sure on piston/bore size but, I'll be figuring it out soon myself because I added a donor 8 3/4 rear end with 11in factory brakes and something's weird in the pedal. But so far from what I can find, these didn't come with 11in rear brakes with power discs up front, just the 10". I could be wrong though
20211028_220542.jpg
 
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