Grabbing Rear Brakes

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mjabbasi
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Grabbing Rear Brakes

Post by mjabbasi »

Ok so here I am with my first issue with my '63 convertible:

1. Rebuilt Booster, new Master Cylinder, new front/rear brake pads installed, following which:

2. Test drive over a short distance fine, do the brake adjusting reverse stops a few times, everything seems good.

3. First 'long' 30 min drive results in the rear brake lights staying on when I reach my destination and turn off the engine. Light go off after about 20-25 mins and after resting for about 2 hours, come home uneventfully. Brakes work fine both ways.

4. Second 25 min drive, brake lights off when I reach my destination. Return home after a few hours and rear brake lights on. After 15-20 mins they go off but brakes again work fine both ways. I assuming the new rear brake pads may need adjusting, have them backed off very slightly.

5. This past Sunday morning went on a longer drive. Reached my first destination in about 25 mins and rear brake lights were on after engine turned off. After around 20 mins I tap the brake pedal with my foot and the brake lights go off. Start the car and set off again, lots of stop and go and braking action along the way and weather pretty hot at 38 degrees. After around 15 mins I notice the car struggling to go forward under its own power and I'm having to keep pressing the pedal to pick up speed. If I release the pedal the car starts to slow down itself with my foot off the pedal so I depress the pedal to pick up speed. Engine temperature slowly rising too. I reach my next destination, park to a stop and white smoke is puffing out from the rear wheels with a burning smell. Front wheels are fine. I put it in D to see if I can move forward but no. The car is jammed still and won't budge and the brake pedal is rock hard and will not depress. I turn off the engine and the rear wheel area continues to smoke for a good 30 mins and the rear brake lights are again on. After about 1 hour someone informs me that my rear brake lights have gone off as things seemed to have cooled down. I then leave after about 30 mins and drive home uneventfully, a 15 mins drive, normal braking/pedal action along the way and when parked and the engine turned off at home, rear brake lights are off but the burning smell lingers for a while.

So this is the scenario. Both rear brakes dragging and sticking once warmed up. When I replaced the Master Cylinder (henceforth 'MC') with a new one, I could not recall whether it was for the Lincoln or my '61 T-Bird as both units look almost identical. I spoke to a friend and he said its possible the new MC I replaced may have a different piston clearance from the Booster pin as compared to the cars old MC (which I later also had rebuilt with a kit and kept as a spare if ever needed) and one thing I should try is to unbolt the MC from the Booster and very lightly tap some grease on the head of the Booster pin, replace, bolt and again unbolt and remove and see if the grease has been 'smudged' or in any way come into contact with the wall of the MC piston and if it has, the Booster pin (which is adjustable like a screw) needs to be backed off maybe half a turn and there needs to be a slight clearance between the head of the pin and wall of the MC piston, they should never constantly touch when installed.

Now I recall I had a similar problem many years ago with another '61 T-Bird I owned at the time. MC leaked, rebuilt it with a kit and when reinstalled and tested, the brakes jammed up as the MC seized once warmed up. In this scenario, its only the rear brakes that are jamming up. In this situation what should I do? Check the MC piston and Booster pin clearance? Replace the MC with the cars old one I had rebuilt and test it out to see if the same thing happens? When the brake pedal is depressed (and with our road/traffic conditions that happens a lot with the stop/go driving) the MC is pushing the fluid out but as things warm up and get hot it seems the brake fluid is not returning to the MC causing it to jam up. Braking action is perfect when cold but after 15-20 mins when everything reaches its std operating temperature, that is when this starts to happen. Something is causing the rear brakes to activate and drag once hot but not return except once things cool down. Could this new MC be defective or specific to the T-Bird only in some way? Could the rear brake hose (which I have not replaced and the previous owner of the car cannot recall if he did either in the 5 years he owned the car) be internally collapsing when hot owing to the effect of the new rebuilt Booster and new MC? Braking action was ok prior to these rebuilds/replacements but not perfect (the car would not screech to a halt) till one day when the pedal went all the way to the floor and the brakes failed as I was backing out the driveway (no mishaps thankfully) and that is what prompted me to rebuild the Booster, replace the MC and all brake pads. Also there is no brake fluid leak of any sort.

Sorry for the long post but I felt it best to describe in precise detail what happened in order to get the best diagnosis.
Moin Abbasi
1961 T-Bird Convertible (Montecarlo Red)
1962 LC Sedan (Nocturne Blue)
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Re: Grabbing Rear Brakes

Post by action »

If this is - Rear brakes grabbing and dragging .... and the front brakes do not
AND This is a single reservoir MC with unmodified braking system with drums in rear

Then the issue is
Rear brake springs weak or broken
Rear wheel cylinders fouled or full of debris
Rear brake shoes are not radiused and/or have debris in the lining
Rear brake drums have not been machined when the new brake shoes were replaced
Rear brake shoe adjusters were not adjusted correctly

Need clarification -
Is the MC a single reservoir MC?
Has there been any modification of the brake system
When the new friction lining was replaced, was there any machine work?

Action
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Re: Grabbing Rear Brakes

Post by mjabbasi »

Is the MC a single reservoir MC? Yes, the standard single reservoir MC.

Has there been any modification of the brake system? Absolutely not. As per original.

When the new friction lining was replaced, was there any machine work? The drums were turned at some point by the previous owner. The brake pads looked quite thin so I decided to replace them (for all 4 wheels) and the new ones were of course thicker which is why I suspected they might be rubbing against the drums when the car is moving when I made those first 2 trips, so we moved the star brake adjuster screw further back by 2 notches but then this happened.
Moin Abbasi
1961 T-Bird Convertible (Montecarlo Red)
1962 LC Sedan (Nocturne Blue)
1963 LC Convertible (Premier Yellow)
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Re: Grabbing Rear Brakes

Post by Dan Szwarc »

Replace the shoes springs. They are the only thing that pulls the brake shoes away from the drums.
They should be changed every brake job.
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Re: Grabbing Rear Brakes

Post by action »

As stated above the springs retract the shoes. They do not last forever.
In addition to that new shoes on old machine surface of the drum may not be the best.
The new shoes can catch on the old drum surface.

The edges of the drum can be catching on the new shoes. And it will be difficult to make a good adjust with the "star" wheel since the new brake shoes rarely have the exact same engagement of the drum as the old shoes. Remove the drums and post a picture of the shoes.

The hydraulics are not a factor since the braking system is stock.

Action
Phoenix - Yeah, it's hot, however it's a dry heat
2006 Lincoln Navigator Limited 5.4l 3V
1996 Lincoln Mark VIII 2DR Coupe Diamond Anniversary 4.6l DOHC, 4R70W, 3.07
1970 Continental Mark III Triple Black 460 4v, C6, 2.80 (Used for Woodward Dream Cruise or just generally stored in Michigan)
1966 Lincoln Continental 4DR Convertible 462 4v, C6, 3.00
1966 Mercury Park Lane 4DR Breezeway 410 4v, C6, 2.80
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Re: Grabbing Rear Brakes

Post by mjabbasi »

Oh I wasn't aware about the springs. Yes I have 2 sets of brake rebuilding kits which include new springs so I can get them changed. However, how come it doesn't happen when everything is cold and only when it warms up and gets hot?
Moin Abbasi
1961 T-Bird Convertible (Montecarlo Red)
1962 LC Sedan (Nocturne Blue)
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Re: Grabbing Rear Brakes

Post by Dan Szwarc »

Because warm springs lose their strength. You’re on the edge of friction levels.
Asp make sure the backing plates are not rusted or terribly worn where the shoes rub.
If badly worn with grooves, weld them up and grind them down to flat.
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Re: Grabbing Rear Brakes

Post by frasern »

There is a residual check valve in the M.C. which could be at fault, which would also explain the brake lights sticking. I had a similar issue with a 62 F700, very different system, but the same symptoms.
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Re: Grabbing Rear Brakes

Post by mjabbasi »

I just remembered when we were replacing the rear pads, I had a set of rear pads from my '61 parts car on which we had rebuilt and put new pads on many years ago and I had kept them in storage. When we pulled the ones from the '63 out to 're-pad' I remember telling my mechanic I want the same ones from this car redone with new pads and not use the '61 because I noticed a slight difference in them but he insisted they're identical so now I need to check with him which ones we ended up putting on the car. If they're from the '61, I can have them replaced and add the new springs and see how it goes.
Moin Abbasi
1961 T-Bird Convertible (Montecarlo Red)
1962 LC Sedan (Nocturne Blue)
1963 LC Convertible (Premier Yellow)
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Re: Grabbing Rear Brakes

Post by frasern »

A little known fact, I have done the research! The brake lining was increased from 0.250 to 0.320, and the drums from 11.060 to 11.090 in '63! This is from the specification pages in the '61 manual and '63 supplement. Also the explanation in the "brakes" section, page 8.
This is only going to matter if you use earlier drums with later shoes. Even then, if they are turned 030, you will be O. K.
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Re: Grabbing Rear Brakes

Post by TonyC »

Do keep us informed of the results of your diagnosing, Moin; what you learn may benefit other owners of early-'60s models. I do think that, if new springs don't cure the problem, you should remove the rear cylinders (can be done without disassembling the whole mess), give them a good cleaning, then reinstall and bleed, and check again.

I had the same issue with Frankenstein about three years ago: Rears would grab to the point that the whole car would shake like San Andreas (that's an unstable faultline in California, causes earthquakes there). For a while I did not know what was causing it; then, on a hunch, I bought a new set of rear brake linings, even though the old ones still had enough material on them. Replacing the linings and thoroughly cleaning out everything in there cured the problem. I did not even replace anything in the brakes except the shoes themselves, and not only do the rear brakes work like they should, but even the parking brake started working better.

I'm not dismissing the suggestions of worn hardware in yours; that is possible, just wasn't the case with my situation. That's why I suggest keeping us notified of your results.

---Tony
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Re: Grabbing Rear Brakes

Post by tomo »

The brake lights are staying on because there is still pressure on the switch, weak springs will not keep the brake lights on. I suggest that you check the brake pedal free play to turn off the brake lights. It may also fix your rear shoe dragging problem.

There is a return port in the master cylinder and if there is not enough pedal free play the piston will cover that port. When the fluid becomes warm, it expands and creates pressure on the light switch and brakes.
Tom O'Donnell
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1953 Capri Sport Coupe
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