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Discussion Starter #1
I have a 1974 Alfa Romeo Spider. I'm on the verge of giving up on it and have been looking for another Spider in better shape. However, I'd rather not give up on her and I thought I'd look for help in this forum, which has helped me before, before throwing in the towel. Last summer the back brakes got noisy, I brought it to my local mechanic who determined that the calipers were stuck. So we put on remanufactured calipers, new rotors, and pads on both rear wheel. I took it out for a ride and could soon smell the distinctive odor of brake material smoldering. The rear wheels were smoking and hot as hell. After that, I parked it in my garage for the winter.

Having read several threads since then, here and elsewhere, and I suspect it could be the rear brake pressure regulator (sometimes called a brake compensator or proportioning valve, I believe), but I also have read some threads that suggest it could be the brake booster. The master cylinder was changed about two years ago.

I would be very grateful for any thoughts on the most likely cause of my remanufactured rear calipers locking up to the points that the brakes smell and smoke
 

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86 Veloce
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What shape are the flexible brake lines in? If they have crud in them when you step on the brakes, the fluid goes to the caliper but cant relieve pressure properly. Loosen the bleed screw, take a piece of hose from it to a jar with brake fluid in it and pump the brakes a few times. Some nasty old fluid may come out, you may feel pressure and then release, spewing out a clog. Dont let you MC go dry while you are testing each line....
 

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But Mad North-Northwest
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10,180 Posts
Not the booster. Most likely a bad rear brake hose: they fail internally. If not that could be the proportioning valve but they don’t typically fail like that.
 

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Discussion Starter #4
Thanks. Would that make sense if both rear wheels heat up and smoke? Is there a hose that goes to both wheels? I figured that if both wheels lock up it must be something that affects both.
 

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But Mad North-Northwest
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10,180 Posts
Yes. Rear brakes are linked. On a '74 it goes from master cylinder -> differential pressure warning valve -> brake proportioning valve -> rubber hose -> T-fitting -> rear brakes

The booster and MC are shared between the front and rear brakes, so really can't cause just the rears to lock up. It's probably the hose.
 

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Just random thoughts...
Pinpoint the heat location the best you can. The problem could be in the inner hubs. Could be bad wheel bearing or differential.
Inspect any scrubbing/wear points on the rotors, pads and calipers for clues.

If it were me, I would put the rear of the car on secure jack stands.
Chock the front tires. Take rear wheels off. Start engine only when rear wheels are cold. Have a buddy accelerate and tap the brakes while you observe safely beside the car to tell where the heat and is coming or I see any physical clues of what is going on. If you do this, do it at your own risk. An option is to have a mechanic put it on a lift and troubleshoot.
 
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