164 brakes locking on

[C M Smith <cmsmith@domain.elided>]

This happened to me but only the rears locked on. Basically destroyed the 
rear brakes. No cause could be identified by my mechanic.

To repair I put a new handbrake cable on, new pads, new rotors, and 
complete caliper seal rebuild kits. The handbrake actuator on each caliper 
was also cleaned and lubed. I still worry that the cause was not identified.

Also, I have driven a 164 recently with "hard" brakes as if the brakes were 
not working as well as they should. Could be aftermarket pads, or could be 
a fault. I find brake system defects intolerable, they just shouldn't happen.

If you find out why yours locked on let me know. The MC is a known trouble 
spot but usually one front and the opposite rear are affected by an MC 
failure. Also, the brake flexible hoses are known to crap out now and 
again. This normally affects only one brake at a time.

The Handbrake could jam on but that should be fairly obvious, it can't jam 
on while driving without someone pulling the lever.

I suspect my handbrake adjuster screw jammed on one brake. The handbrake is 
auto self adjust by means of a threaded rod (screw) inside the caliper 
which forces the piston to maintain a constant clearance of about 2mm. As 
you apply the handbrake the rod pushes the piston in to apply the brake and 
also turns. if it turns far enough, the brake adjusts and the piston 
retracts less than it was applied. It is conceivable that a burr or other 
defect on this internal rod could cause the brake to self adjust on too 
hard, taking up the clearance on one brake. Subsequent heating effects 
would eventually apply  both rear brakes as the cable connects left and 
right brakes and automatically moves to equalize the pad clearance. No 
clearance will eventually spread to both brakes via the cable.

Just a theory.




Michael Smith
Calgary, Alberta
Canada
91 Alfa 164L, White, original owner

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