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)
1963 LC Convertible (Premier Yellow)
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mjabbasi
Addicted to Lincolns
Posts: 1930
Joined: Thu Jun 07, 2001 1:01 am
Location: Karachi, Pakistan.
Contact:

Re: Grabbing Rear Brakes

Post by mjabbasi »

Sorry for the duplicate post, something to do with the internet connection and cannot find a way to delete the other post.
Moin Abbasi
1961 T-Bird Convertible (Montecarlo Red)
1962 LC Sedan (Nocturne Blue)
1963 LC Convertible (Premier Yellow)
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