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Disc brake conversion is still not really "right"

Dan Harris said:
Need to use “no fling” grease, mopar had a special grease that would not work out around seals. Regular wheel bearing grease will just make a mess. I think Lucas makes a farm implement grease with similar “no fling” properties .
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The seal leaking that much may indicate more trouble. Check the end play adjustment of the axles as well as the bearings for wear.
 
Big Bad Dad said:
The seal leaking that much may indicate more trouble. Check the end play adjustment of the axles as well as the bearings for wear.
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Replaced with green bearing in March no problems since. All good
 
RussT Plymouths said:
Are you still running the small piston "A" body slider calipers? Going with a slightly larger piston size caliper like the 73 "B" bodies came with could help your braking. Aspen/Volare calipers have larger pistons and may fit without any mods.
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I have the Aspen 2.75 diameter calipers on my Fury. I had to go to a 1 1/32 bore master cylinder due to not enough volume to the calipers.
 
patrick66 said:
In 2003, I did a disc brake swap from a '73 Duster to my '66 Coronet 500...pretty common then, not so much nowadays! The brakes have always worked, but not to my satisfaction. They've never been really good, just adequate. Here is what I've done since that conversion:

1) Installed a rebuilt power booster and new disc brake dual master cylinder in 2003 when the conversion was done; along with new pads and brake hoses. The calipers from the Duster were in good shape and installed.
2) Five years ago, the LF caliper locked up while I was leaving a car show. Replaced that caliper. Completely replaced the brake fluid at that time with DOT3. Replaced the RF caliper a year later.
3) A few months back, the car took a great amount of effort to stop after just a 15-mile drive! The fluid was low in the front part of the m/cyl, so it was topped off. Later that day, we bled the brakes all the way around. Not much difference. A new master replacement was recommended by a few people, so a new (not r/b) "made in USA" went in.
4) While I was driving the Hot Rod Hundred car run a few weeks back, the brakes once again began to be "flaky". The pedal would go nearly to the floor at times; other times, it was almost normal. I got to a parts store to see if my fluid level was still good and bought brake fluid, just in case. It was normal, but the master cylinder was very hot to the touch...like, just out of an oven hot, but not glowing. The fluid level was normal, however.

So, with this information, I came to the conclusion that perhaps my brake fluid was boiling while I was braking. I'd heard of this, but hadn't experienced it. It was a 220-mile drive, but the moments of using the brakes were few, since we were on State highways for the majority of the run. I've never had a master cylinder be that hot to the touch!

The plan: Check and adjust the adjustment rod in the power booster for proper adjustment; I'm gonna assume for now that it is not. Then, take the car out for a drive around the lake and back home, which is roughly 40 miles at speeds from 35 to 70 mph. If that is not the problem, I'll take the front wheels off and check the discs and the pads for anything out of the ordinary. If things are "normal" again, I guess that's that. If not, I do have new front hoses (still in their bags) that I was going to use on a project that sold several years ago that are the same as the hoses on the Coronet, that I might swap out.

Any ideas? I think I've covered what's up.
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If you re used the old pads, you aren't helping anything. If you have the cash, power stop, or EBC brake pads help. The booster push rod can make your brakes drag, but maybe you should go to a disc booster first, and remember, manual brakes generally use a 15/16 bore.
 
In all of my reading on this subject I haven't seen anyone ask if you are using the disc brake proportioning valve, when doing a swap to disk brakes, all the parts for disc brakes to work properly are needed, the master cylinder,brake booster(if wanting power brakes) and the proportioning valve. Any of the three not being used can result in poor brake function and longer than wanted stopping distance.
 
79Maggiettop said:
In all of my reading on this subject I haven't seen anyone ask if you are using the disc brake proportioning valve, when doing a swap to disk brakes, all the parts for disc brakes to work properly are needed, the master cylinder,brake booster(if wanting power brakes) and the proportioning valve. Any of the three not being used can result in poor brake function and longer than wanted stopping distance.
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Good point. I haven't even looked to see what's in the plumbing. It's been nearly 20 years since doing the original swap.
 
I'm not under the car at the moment. I've got time later in the week to take stock of WTF is up with the Coronet. It ain't going anywhere.
 
patrick66 said:
I'm not under the car at the moment. I've got time later in the week to take stock of WTF is up with the Coronet. It ain't going anywhere.
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Just bustin yer balls a bit. Im kinda curious myself to see wtf it is.
 
I did drive it about twenty-five miles on Saturday to a C&C and a car show. No changes seen, so whatever the problem is, I guess I didn't have enough "My Little Pony" points banked up to make a difference! Or save the world in a game of "Thermonuclear War" with the WOPR computer...LOL!

I had a dream last night where I drove it over to a buddy's house to work on it. We got distracted by ribs and beer. His six-year-old son comes over and says "I fixed your car!"...WHAT? We go over to see what he was talking about "fixed", and he pointed to what he did. "Drive it and you'll see!" he says. Putting my confidence and hope in a first-grader, we go for a drive. Braked like never before! I could stop on the edge of a dime! The little bastard wouldn't tell me what he did to fix the problem!

I have a feeling that when this is sorted, it'll be a similar scenario...not!
 
"I'd piss on a spark plug if I thought it would help!"
 
After considerable thought, several eyeballs on the issue, and consumption of a couple of barley pops, I'm about 93.527% certain that the booster is the issue. It is original to the car, when it had power drums. Just not enough "oomph!" and not enough feel. So, I am calling Booster Steve today and see what I can do to get a proper booster, or if he can convert mine to work with discs.
 
Booster Steve won't be able to convert your single diaphragm unit. He may have some dual diaphragm units for sale. I bought mine from Pirate Jack. It is a 66-70 8" dual booster like the factory would have installed with front discs. The rubber boot that goes through the firewall is larger than the factory ones were so you will have to do a little dremmel work. Here is a pic of the one I got.
I think they have them on Ebay for $250.00. Your master should be fine.
s-l500.jpg
 
Sixpactogo said:
Booster Steve won't be able to convert your single diaphragm unit. He may have some dual diaphragm units for sale. I bought mine from Pirate Jack. It is a 66-70 8" dual booster like the factory would have installed with front discs. The rubber boot that goes through the firewall is larger than the factory ones were so you will have to do a little dremmel work. Here is a pic of the one I got.
I think they have them on Ebay for $250.00. Your master should be fine.
View attachment 1363540
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All of that from Jack's is Made in China. No, thanks. I avoid China-made parts like the plague, whenever and wherever possible. Especially brakes. And yes, Booster Steve claims the Midland booster I have will work for both discs and drums. Right now, I have basically zero boost. It is original to my Coronet, and it IS 56 years old.

Plus, the ebay units just don't look right under the hood of a '66 or '67 B-body. I don't know what kind of warranty the Jack's boosters have, but I've dealt with Booster Steve before on my Imperial booster and have been quite happy with the results.

We will see...!

IMG_20221025_170916050.jpg
 
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patrick66 said:
All of that from Jack's is Made in China. No, thanks. I avoid China-made parts like the plague, whenever and wherever possible. Especially brakes. And yes, Booster Steve claims the Midland booster I have will work for both discs and drums. Right now, I have basically zero boost. It is original to my Coronet, and it IS 56 years old.

View attachment 1364183
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I have the original Midland booster on my 64 Fury that I recently converted with the Dr. Diff kit. My booster works with it. It sounds like your booster just needs to be repaired.
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When the booster comes back to me, I'm definitely installing a heat shield at the inboard two fasteners to the M/C and the booster, to add a bit of a heat barrier for the M/C. Just an added layer of protection for the brakes, IMO.
 
Came across this old post, curious if you determined the heat problem. Way back when I had a similar issue and found the pads were binding in a caliper, not fully retracting keeping contact with the rotor. Problem was so elementary, lol, I had overlooked it until I didn’t.
 
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