63 drum brakes dragging

[Frank D.]

I have a stock drum brake setup and converted to power brakes in 2016…..absolutely no problems for 1,000 of miles until now. Last week the right rear brake started dragging badly when the car got hot to the point it rode home on a rollback. In the process that wheel’s brake drum got warped – so I replaced ALL 4 drums with the ACDelco “Professional” replacements, and put new brake hoses, new Dorman wheel cylinders and shoes on both sides of the rear. Also put new shoes on the front. Carefully bled and adjusted them (with the parking brake loose) and then adjusted the parking brake. Lubed the 6 “slide points” on the backing plate and confirmed the new self-adjusters worked perfectly.

Still have the same problem and I’m stymied…after 20 minutes of driving and moderate braking the car gets a gradually worsening pull to the right and when I got home and the car sat for 20 minutes I couldn’t push it backward or forward at all. At this time front wheel temps were about 106*, left rear was 110* and right rear was 190*. After an hour of cool down I could rock the car around again.

I have now placed two washers under the master cylinder bolts between it and the brake booster (as an experiment) to see if perhaps the brakes were holding pressure when the fluid got hot and completely loosened the parking brake. I can’t imagine the booster push rod clearance suddenly became a problem though.

I’ve done brake maintenance on dozens of cars and never had a problem like this I couldn’t solve.
I will drive the car again on the next cool Florida morning and see if things have improved but any thoughts others might have are appreciated.

[Richard M.]

Re: 63 drum brakes dragging

Frank, I first thought maybe a booster issue then I re-read your post. That right rear 190* temperature tells me the problem is still right rear, as well as pulling right. Maybe totally disconnect the E-Brake cable on that side.

Next step may be to disconnect the self adjuster but not sure how to do that. Is it possible that it's self adjusting too much? I could never understand the principle of how they work.

Rich

[Frank D.]

Re: 63 drum brakes dragging

So good to hear from you Rich, yeah, I'm gonna dink around with the emergency brakes next as you (and the 63 Service Manual) have a "One Side Brake Dragging" section in the Troubleshooting part that says a frozen parking brake cable could be the issue - once the temps in the garage go down from "surface of the sun" to merely "sweltering" I'll rip things apart again (for the 5th time!). (And yes the self adjuster torpedoes are on the correct "L" and "R" sides!)

I DID give a cursory look at the parking brake cable but discounted it when I couldn't see anything physically wrong. As to how the self adjusters work - you've prob seen this but I watch it from time to time because its such a funky '60s-style educational video - its a hoot:

https://www.youtube.com/watch?v=T6qTqJ-tdrE&t=32s

IN THEORY - the brakes can not over-adjust (as the video shows) but who knows, but then I wouldn't expect them to completely free up when things cool down..

[Richard M.]

Re: 63 drum brakes dragging

Frank, I just watched that video. Thanks for posting the link. It actually shows how they can't "over" adjust, at around 2:10 of the video.

My gut is telling me the E-Brake cable on that side may be seized.

Yes pretty darn hot here too. Humidity is brutal. You need some garage door insulation and some AC in there. Maybe a mini-split system would be the way to go if you can't install a window unit. Bad thing is you'd loose it all once the big garage door opens.

Rich

[Bill M.]

Re: 63 drum brakes dragging

There is a small port called the compensating port that allows brake fluid to expand back into the reservoir when the fluid heats up and expands. If that port is plugged, when the fluid expands with heat, it applies the brakes. The smaller port in this picture of my '65 master is the compensating port:

100_3457.jpg

[Frank D.]

Re: 63 drum brakes dragging

I appreciate that Bill and understand, but I'm pretty certain its just the right side rear with the problem as another test drive today produced the same symptoms even after I loosened the emergency brakes at the adjuster and shimmed the master cylinder off the booster. I will pull the parking brake cables off each side and see if they are frozen.

My worst case scenario is that the right rear wheel bearing is heating up on that side and transferring into the brake ass'y - is that even a possibility ? The entire rear including a complete trailing arm rebuild was done by a top pro last summer so I'm doubting that...and I would expect to hear a noise or feel something if that bearing was an issue...

I've also ordered a spring kit just in case the shoe return springs or worn or tired...

[Bill M.]

Re: 63 drum brakes dragging

I appreciate that Bill and understand, but I'm pretty certain its just the right side rear with the problem as another test drive today produced the same symptoms even after I loosened the emergency brakes at the adjuster and shimmed the master cylinder off the booster. I will pull the parking brake cables off each side and see if they are frozen.

My worst case scenario is that the right rear wheel bearing is heating up on that side and transferring into the brake ass'y - is that even a possibility ? The entire rear including a complete trailing arm rebuild was done by a top pro last summer so I'm doubting that...and I would expect to hear a noise or feel something if that bearing was an issue...

I've also ordered a spring kit just in case the shoe return springs or worn or tired...

When my comp port was plugged, it applied all 4 discs evenly. With the drums, a weak return spring might cause just the right rear to apply? I see you have that covered.

If the parking brake cable isn't the problem, and if it is just the right rear locking up due to wheel bearing heat, I would consider an internally collapsed hose that is keeping the pressure from feeding back to the master. I haven't had that happen, but have read it can happen...

[Frank D.]

Re: 63 drum brakes dragging

When my comp port was plugged, it applied all 4 discs evenly. With the drums, a weak return spring might cause just the right rear to apply? I see you have that covered.

If the parking brake cable isn't the problem, and if it is just the right rear locking up due to wheel bearing heat, I would consider an internally collapsed hose that is keeping the pressure from feeding back to the master. I haven't had that happen, but have read it can happen...

First thing I did was change both rubber hoses and wheel cylinders on both rear sides Bill....

I'll know more when I tear things back apart this weekend. Really hoping its just a parking brake cable. The one thing I haven't done yet is drive the car to the point of dragging then crack open the right rear bleeder screw to see if there is pressure there. May do that before tearing into more things and "shooting the parts cannon at it". (My mechanic brother's euphemism for replacing parts to solve a problem).

[Frank D.]

Re: 63 drum brakes dragging

Well I got the old parking brake rear right and left cables out and they are indeed frozen, I certainly can't budge them by hand but I think they moved a bit with the leverage of the cockpit handle when I used the parking brake. I have the new cables and the lengths match the old ones but waiting on an equalizer and some clamps/grommets from Zip. If these parts aren't THE problem they are certainly A problem... More to follow.

[Richard M.]

Re: 63 drum brakes dragging

Frank,

Glad you figured it all out. Strange that both cables were seized and only causing the right side problem. Maybe because it's the longer cable.

Rich

[Frank D.]

Re: 63 drum brakes dragging

Tackling this today - front brake cable moves smoothly, no issues, BOTH rears are seized up completely; the Corvette Central repro cables are decent and I got their last 1963 right side parking brake cable... If anybody is doing this try to keep the original rubber frame grommets for the cables just aft of the equalizer - the repros are awful and just hardware store grommets with large openings that will allow road crud and water into the cable sheath - better to resurrect the originals with some cleaning and Aerospace 303.

[Harry S.]

Re: 63 drum brakes dragging

Frank, if this is the fix, it will help everyone else.

Thanks for the detailed descriptions

[Frank D.]

Re: 63 drum brakes dragging

I won't know for sure until the hardware arrives from Zip, the original equalizer just fell apart and a few clamps were beyond saving...you can see how the right rear brand new drum got baked to a golden hue by the dragging brake - I'll report back if all of this fixes the issue...

[Richard M.]

Re: 63 drum brakes dragging

Frank, So it looks like both cables were getting worse over time. I'd imagine they were original so probably about time now anyways.

Just to be safe you may want to rough up all 4 rear brake shoe linings with some heavy grit sandpaper. The shoes could have gotten glazed from all of the heat when stuck.

As far as that goldenized drum from the right side. Could it now be damaged? I don't know. It may be okay but you may want to research. I just did and said if drums reach 200* it will cause fade. I didn't see anything about drum damage at that temp though.

Some interesting reading over Here on HAMB.

Rich

[Patrick B.]