58 Coronet rear brake issues

[samdjr74]

Hello all,

 

I just joined the group last night. I stumbled upon it doing some research on how to fix the brakes on my 58 Dodge coronet. Recently I installed the AAJ front brake kit with a new dual MC and Willwood proportioning valve. Shortly after getting everything adjusted and working correctly my rear brakes locked up and wouldn't let go until I dropped it into neutral then drive. I readjusted the rear drums and it was fine for a few days. Then the problem came back. Not as bad as before but still not good. Could the problem be related to the new MC putting too much pressure on the original rear brakes or is this just a sign that my rear brakes are shot and need a rebuild? my fear is I rebuild the tears and I still have the issue because of the MC. For some details, the car still has manual brakes, torque flight tranny and a 325 poly that was modified to a 325 hemi years before I got it.

 

Thank you,

Sam

[Plymouthy Adams]

ensure that there is some play in the master cylinder rod as the piston must travel completely to the rear against the stop to relieve all residual pressure....second item is to ensure that the rubber flex at the rear axle is not semi-plugged/collapsed and prevent quick unrestricted return of fluid from the wheel cylinders...quick check for this is when in locked condition open a single rear bleeder...if it frees the wheels odds are one of the two situations above...

[samdjr74]

8 minutes ago, Plymouthy Adams said:

ensure that there is some play in the master cylinder rod as the piston must travel completely to the rear against the stop to relieve all residual pressure....second item is to ensure that the rubber flex at the rear axle is not semi-plugged/collapsed and prevent quick unrestricted return of fluid from the wheel cylinders...quick check for this is when in locked condition open a single rear bleeder...if it frees the wheels odds are one of the two situations above...

Thanks! The rod does have play. I will look at the flex line next. Problem with the test is I only find the problem when driving so getting under the car, opening the valve,  etc might be tough. It might be easier to replace the flex line and see if it works

[Plymouthy Adams]

dropping it in and out of gear has nothing to do with the brakes on the rear....the time you are doing that may allow a partially collapsed hose to bleed...as you went disc up front....are you using residual valves plumbed inline?  Another thing of importance is if you went to a modern master or stuck with your old unit....the old unit has a bleed hole in the rear of the reservoir serviceable through the master fill cap...if plugged, this will prevent a full return...again...ensure that you have play and that the piston is at its most rearward stop position.

Edited June 30, 2019 by Plymouthy Adams

[samdjr74]

1 hour ago, Plymouthy Adams said:

dropping it in and out of gear has nothing to do with the brakes on the rear....the time you are doing that may allow a partially collapsed hose to bleed...as you went disc up front....are you using residual valves plumbed inline?  Another thing of importance is if you went to a modern master or stuck with your old unit....the old unit has a bleed hole in the rear of the reservoir serviceable through the master fill cap...if plugged, this will prevent a full return...again...ensure that you have play and that the piston is at its most rearward stop position.

Let me explain what's happening. I put the car in reverse to back out of the garage. When I got to drive, the car won't budge, you can feel the rears are locked and when you give it gas one of the wheels will break free and spin. So if I drop it into neutral, then reverse, then neutral again and finally drive it breaks free fully and I can drive it. It doesn't happen all the time but it seems to be more prevalent when it's damp outside. When it's really bad the wheels will lock up after every time you apply the brake. I'm not using a residual valve in the line unless there was one from the factory I'm not aware of. Basically I didn't touch the rear brakes or brake line. I only worked on the front brakes and added a second brake line for the fronts, replumbed the line from the T fitting to the rear and installed the proportioning valve on the rear line right below the MC. The MC is new out of a 76 Dodge Dart as per Roger's advice.

[Plymouthy Adams]

sounds like the rocking action of forward and reverse is pushing the piston that last little bit needed for full release.....investigate you major and minor adjustment and the very fact that the piston of the wheel cylinders are fully returning by their very return springs....these pistons do get crud behind them and build a ring....

[kencombs]

Only happens in reverse?  And one wheel breaks free with you try to accelerate?  I'd pull the rear drums and inspect for loose/broken parts or fluid leaks.  Start with the one opposite the one that breaks free.

[samdjr74]

3 hours ago, Plymouthy Adams said:

sounds like the rocking action of forward and reverse is pushing the piston that last little bit needed for full release.....investigate you major and minor adjustment and the very fact that the piston of the wheel cylinders are fully returning by their very return springs....these pistons do get crud behind them and build a ring....

I need to get the hub puller before doing anything else but I got a strange feeling the shoes and cylinders are gummed up and shot.

[samdjr74]

2 hours ago, kencombs said:

Only happens in reverse?  And one wheel breaks free with you try to accelerate?  I'd pull the rear drums and inspect for loose/broken parts or fluid leaks.  Start with the one opposite the one that breaks free.

No it happens more going forward, meaning the car reverses fine but won't want to go forward until I jerk it a little. Sometimes it happens in reverse but not often. But yes one wheel will usually break free. The other thing is when going in reverse you don't notice the problem.

[kencombs]

47 minutes ago, samdjr74 said:

No it happens more going forward, meaning the car reverses fine but won't want to go forward until I jerk it a little. Sometimes it happens in reverse but not often. But yes one wheel will usually break free. The other thing is when going in reverse you don't notice the problem

OK, your previous description stated that it happened when backing out of the garage.  Locking going forward can well be due to shoes contaminated with fluid.  Wet shoes always grab worse going forward.  After doing this, does it free when reversed? usually a sticky shoe will do that.  I really doubt that the cylinders/pistons are the issue as the return springs are usually strong enough to overcome that, unless the piston is overextended, but in that case it wouldn't release at all.

[samdjr74]

1 minute ago, kencombs said:

OK, your previous description stated that it happened when backing out of the garage.  Locking going forward can well be due to shoes contaminated with fluid.  Wet shoes always grab worse going forward.  After doing this, does it free when reversed? usually a sticky shoe will do that.  I really doubt that the cylinders/pistons are the issue as the return springs are usually strong enough to overcome that, unless the piston is overextended, but in that case it wouldn't release at all.

Here's the main issue, it seems to happen more when it's wet or damp outside, think hi humidity for example and because the problem is so severe, I haven't felt comfortable taking it out around the block to see if the issue improves. I'm going to need to do that once I get the new starter in and really make some good notes on what's happening.

[kencombs]

1 minute ago, samdjr74 said:

Here's the main issue, it seems to happen more when it's wet or damp outside, think hi humidity for example and because the problem is so severe, I haven't felt comfortable taking it out around the block to see if the issue improves. I'm going to need to do that once I get the new starter in and really make some good notes on what's happening.

OK, with that info it really makes me believe the shoes are at fault.  brake fluid, water and rust really make shoes grabby.  Is that a word?  But, you know what I mean.  It is amazing how clean cast (inside of drum/outside of rotors) will form a film of rust. '

 

I have a '97 F150 since new and if it sits for a few days in humid weather ( most of the time in OK)  the disk brakes will nearly put you into the steering wheel, but only on the first stop.  Being disks they don't stick though.

[samdjr74]

1 hour ago, kencombs said:

OK, with that info it really makes me believe the shoes are at fault.  brake fluid, water and rust really make shoes grabby.  Is that a word?  But, you know what I mean.  It is amazing how clean cast (inside of drum/outside of rotors) will form a film of rust. '

 

I have a '97 F150 since new and if it sits for a few days in humid weather ( most of the time in OK)  the disk brakes will nearly put you into the steering wheel, but only on the first stop.  Being disks they don't stick though.

I just ordered the hub puller, hopefully that will be here next week. And I do know what you mean, grabby works for me Thanks!

 

[Plymouthy Adams]

I would venture to say this was happening before the front disc were put on...else you sot something not quite up to par on your install......

Edited June 30, 2019 by Plymouthy Adams

[samdjr74]

14 hours ago, Plymouthy Adams said:

I would venture to say this was happening before the front disc were put on...else you sot something not quite up to par on your install......

I don't think it was happening before the disc upgrade as I never noticed it. This is why I think there's something going on with the way the new MC is working with the old drums. I didn't touch the rear brake lines except to disconnect it from the T fitting to reroute it to a separate line for the dual MC.

[kencombs]

How does your MC bore for the rear brakes compare to the original?  Different size moves fluid at different rates. Could be the reason.

[samdjr74]

Just now, kencombs said:

How does your MC bore for the rear brakes compare to the original?  Different size moves fluid at different rates. Could be the reason.

I would need to check, I went with what AAJ recommended. I need to call Roger today to check out his rear disc set up but I'll ask him about the MC. The main difference is the new MC is a dual reservoir where the old one was a single reservoir unit. 

[soth122003]

Does it grab continuously or does it get better after the first few stops as you drive? If it gets better then it is probably the shoes as the heat will evaporate the moisture. If so then change the shoes cause when brake fluid soaks into them, it stays like a bad house guest.

 

Joe Lee

[samdjr74]

2 minutes ago, soth122003 said:

Does it grab continuously or does it get better after the first few stops as you drive? If it gets better then it is probably the shoes as the heat will evaporate the moisture. If so then change the shoes cause when brake fluid soaks into them, it stays like a bad house guest.

 

Joe Lee

It seems to get "better" the more it's driven but that first few blocks is a touch scary. Right now I'm waiting on my starter to get rebuilt, it died last Friday. Once I get it back in, test it and see what else is going on I'll address the brakes. I just ordered a hub puller so that should be here next week. But I'm really thinking about putting discs in the rear. This would make life much easier down the road the next time I need to work on the brakes.

 

[samdjr74]

So I never came back to the thread with the update. Turns out the flex hose collapsed and was acting like a check valve. Once it was replaced, everything is working fine

[greg g]

Wonder if you have a leaking whee cylinder??  Corrupted brake shoes will grab and lock up also.

[samdjr74]

51 minutes ago, greg g said:

Wonder if you have a leaking whee cylinder??  Corrupted brake shoes will grab and lock up also.

It's possible. This winter I'm installing rear disc brakes. I just got the kit in form AAJ yesterday and need to order a new MC and parts but that will eliminate the problems with those tapered axles and drums.