1966 coronet 440 rear and front brake question

[Sewalsn20]

Hey guys, just finished up the rear brakes on the 66 coronet i got recently that i posted about and i have some questions about the front brakes. it's 10" drums all the way around. the front brakes are gutted so ive got no reference. the shoes front and back are interchangeable, but was wondering if the upper springs, self adjuster cable, adjuster bracket, star adjuster and guide for the cable are the same too as the back. i got the master brake kit for the car but the shoes i got require the long yellow spring on both shoes per wheel and the kit i got gave me one yellow upper spring per wheel. if all the parts are the same i'll be able to get them from the parts store tomorrow and get the front done too on my last day off! i'm going to post a pic here of what i think my fronts should look like, they look very similar to my rears. TIA.

 

[pnora]

As far as I know self adjusting brakes were not available in 66. However you can update them to self adjusting and they should take the same hardware front to rear.

 

[R/T Boy 67]

The pictures are correct. One long spring, one short spring on top. Self adjusters were used in 66.

 

[Mariposa Mike]

I posted a question within my Dot 5 fluid post but did not get an answer. It would be similar to this post. It's a 66 Charger and does have the self adjusters. And 10 inch brakes. The springs on top are one yellow and one red or near red. One was slightly (1/4 inch) longer than the other but which way do they install? Yellow on the left or right? The reach looked the same. MrDee previously posted a color picture of the brakes/springs installed and the passenger rear had the yellow spring on the right. When I took mine off the yellow was on the left. The self adjuster cable side. Anyone know the difference and the reason for two different springs? Manual does not say anything I could find.

 

[AR67GTX]

My 64 Plymouth Sport Fury I bought in 68 had self adjusting brakes. They caused me some problems with the rear brakes.

 

[Mariposa Mike]

Today I replaced the left rear wheel cylinder which was frozen inside just like the pass rear. That might be why I was having issues with the self adjusters. Before one began leaking the adjusters kept getting tighter. But w/o the pistons moving in the cylinders that might have been the issue. Lot of crud in the cylinder too but with it having Dot 5 fluid they did not have a lot of corrosion inside the cylinders. Still, they locked up. Time will tell but I have backed off those adjusters three times in the last month due to the brakes overheating. If it happens again they are coming off. Also went on line for a deeper search into the color of the springs and what I found is that the yellow on the rear goes to the shoe with the e-brake. Secondary I think it's called which is counterintuitive since it does more work.

Now I have to move to the front which look like they have been serviced more recently but I don't trust any previous work done on the car now. And the drum brakes continue to improve.

 

[pnora]

Today I replaced the left rear wheel cylinder which was frozen inside just like the pass rear. That might be why I was having issues with the self adjusters. Before one began leaking the adjusters kept getting tighter. But w/o the pistons moving in the cylinders that might have been the issue. Lot of crud in the cylinder too but with it having Dot 5 fluid they did not have a lot of corrosion inside the cylinders. Still, they locked up. Time will tell but I have backed off those adjusters three times in the last month due to the brakes overheating. If it happens again they are coming off. Also went on line for a deeper search into the color of the springs and what I found is that the yellow on the rear goes to the shoe with the e-brake. Secondary I think it's called which is counterintuitive since it does more work.

Now I have to move to the front which look like they have been serviced more recently but I don't trust any previous work done on the car now. And the drum brakes continue to improve.

One thing that gets overlooked is the adjusting sequence. The emergency brake needs to be fully backed off so the shoes seat properly on the upper anchor points. Then the service brake gets adjusted. Then the emergency brake gets adjusted. Out of proper adjustment can result in brake drag.

 

[Mariposa Mike]

That might make sense but.....if the ebrake is not adjusted correctly then why would there not be drag when I reinstalled the shoes and new cylinder? I put the same shoes back on and adjusted them loosely so that there would not be drag. This morning I drove into town ( seven miles) for a small get together of gearheads and the brakes were smoking from both sides. The wheels were hot of course. Coming back home I avoided using the brakes as much as possible but could feel the drag a little. Not smoking when I got home but something is wrong. The brakes have been converted to duel master and I do not see a proportioning valve. I might start a new thread on this issue to get the most/best response but I have been working on MOPARS for a long time as a shade tree tech and never ran across a problem like this. But then I have never changed to a duel master either. Is it possible the master cyclinder could be causing the issue?

Befuddled Mike

 

[Cranky]

As far as I know self adjusting brakes were not available in 66. However you can update them to self adjusting and they should take the same hardware front to rear.

I've had two 66 B body cars....one was bought new by my family and both had self adjusters on them. When I got the first one, it still had the original brakes on it.

 

[AR67GTX]

What about the rear rubber line to the axle line? Has it been replaced to your knowledge? If it’s old and breaking down it can hold pressure in the rear line and wheel cylinders and keep the brakes applied.

Another issue since you have converted to a dual pot master could be the pushrod if it’s not allowing the piston to retract far enough to open the compensating port on the pot for the rear brakes and it’s keeping pressure on them as a result. On power brakes an easy check is to loosen the bolts on the master cylinder which gives the piston more room to retract and release pressure. If it releases pressure then the pushrod needs to be shortened. Not so easy to do on a manual brake master with the nuts under dash.

Just a couple of thoughts.

 

[Mariposa Mike]

It's definitely been replaced at some point. Looks and feels normal but I have no idea WHEN it might have been replaced. I've had the car just about one year. As mentioned in an earlier post the cylinder pistons were frozen in place and now I'm thinking that might have been from overheating. Not a lot of corrosion and the rubber boots were still flexible but there was sludge in the cylinders that might have been burnt fluid now that I'm having this issue. The idea of the pushrod not allowing the piston to retract is a good one. When we bled the brakes I of course did not do that with the engine on activating the power brake booster. But my wife had to push really hard on the pedal to get the pedal to drop to the floor with the bleed screw open. That was unusual. So I opened the screw one more time and asked her to push to the floor which she was able to do but it again took a lot of pressure and time.

I have not jacked the car up to see how much drag is on the drums now but if it has normalized or remained tight that should tell me something. And that might be the master cylinder port.

 

[AR67GTX]

I didn’t realize you have power brakes. The next time they seem to be locked up, loosen the bolts holding the MC to the booster a little and if they immediately free up then you will have found the issue. Good luck. Brakes can be kind of frustrating.

 

[Mariposa Mike]

AR67GTX.....If the rod needs to be shortened is there a rule of thumb for that? And if you know, can that be done on the car? I'm going to lift the rear this morning and see if they are still tight, etc.

 

[Mariposa Mike]

Update. Jacked up the rear and both wheels spin w/o drag. Started the car and applied the brakes and no drag. applied the brakes and no drag. WTF? Took it for a short drive and no drag. Had the wife repeat and this time there was a little drag upon release. Enough that it would heat the drums up when driving. Started the car and same results but a little more drag. Loosened the M/C nuts and could only move it back about 1/4 inch due to the rear brake line hitting the shock tower. Still had the same drag until I jiggled the M/C and the wheels free up. So I believe it is the push rod.

Looked in the manual and it appears the rod protrudes from the booster a bit but not much. Also has a rounded/ball end. So how do we shorten these? Complete removal of the booster, etc or can it be done in place?

 

[AR67GTX]

Not that I’m familiar with. I just had the booster rebuilt on my 67 and they insisted that I include the pushrod to the master cylinder, presumably so they could set it up for a standard penetration into the booster. You might have to experiment with loosening the MC and wedging it forward, start the car and have someone press on the brake and release it while you watch the fluid in the bowl. When the piston retracts enough to uncover the compensating port there is a squirt into the bowl from the line pressure being released. At that point it should be good. From how far the MC is wedged forward you can judge how much the push rod needs to be shortened. It needs to be pretty close but I don’t think it’s something you have to get down to the hundreds of an inch - just short enough so the cylinder fully uncovers the port.

Maybe one of the guys here knows the dimension. Or you can measure the retracted piston depth in the pushrod seat, to the face of the master cylinder. Then measure the protrusion of the pushrod from the mounting face of the booster and make sure that it is just slightly shorter than the measurement from the MC.

 

[AR67GTX]

The acorn like tip is usually threaded to adjust length. Actual adjustment is a little tighter than I said above. I found a reference to .020” play - just a hair more than necessary to let the piston fully retract.

 

[Mariposa Mike]

Looks like I will be dismantling the dual unit to look at the rod. But I should likely try determining how much less rod length is needed by the method you suggest before that. I have seen that squirt into the bowl on M/C's before but did not totally understand what was going on. Thanks for the advice.

I had also been thinking that maybe the brake shoe springs were not strong enough. The overheating back there might have taken some temper out of them. But given the drag lessoned by moving the M/C around as much as I could likely points to the M/C.

 

[Mariposa Mike]

After the wife got back from shopping I tried two more tests. One with tools jammed in behind the master to get an idea of how much adjustment is needed and the look at the open M/C for bubbles to indicate internal travel. Both with engine running. After using the tools to create about 1/4 inch clearance I checked the rear wheels and they were tough to turn again. Moved the M/C manually and no love. Then removed the cap to look for bubbles and had a little geyser when the pedal was pushed but nothing on the return of the pedal. Did that one more time because I did not see anything in the front chamber. Second time I did but not as great a splash as the rear. And the wheels are still tight. Earlier I was able to get them free again by moving the M/C manually. But not now.

I can't figure this out. May have to start throwing parts at it. Or go back to a single reservoir master. Looking at the manual for 1966 it shows two brands of boosters and neither one looks the same as what is on this car. So maybe that was changed at the same time as the duel master. This booster has a raised square imprint rather than being smooth. Frustrating to say the least.