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I have a 37 Packard 120 and am having problems with the brakes locking up. A very experienced mechanic rebuilt the entire brake system all the way from master cylinder to each and every wheel. He said the set-up process was very difficult. He followed the set-up and adjustment procedures as outlined in the Packard shop manual yet as he set things up, one by one he had to work at extensively adjusting each wheel because first one would lock up and then another and then another. Thought all were good to go and the car drove well for 100 miles and then this year for no apparent reason, the left rear locked up when coming to a stop at a light. More adjusting and seems to be working but based on its history, not confident the problem won't come back at the worst possible time. Has anyone had this problem? Is there a trick to setting up the brakes? As I mentioned, everything is new in the entire system. Any input would be appreciated. Hard to find people who still work on these older cars. Thanks, Bob

My first reaction is to think something is fundamentally wrong with either the parts or the installation. Hydraulic brakes are inherently self-equalizing, meaning the hydraulic forces exerted on the shoes are equal, left to right; thus, assuming proper parts and installation, small differences is shoe adjustments from wheel to wheel should not result in unequal braking force. So having first one wheel lock up, and then another, and then another, each to be "corrected" by an adjustment, would only make sense if you had mechanical and not hydraulic brakes.

Assuming you've checked the obvious, leaking grease seals and wheel cylinders, sufficient free play at the brake pedal to relieve the hydraulic pressure when the pedal is relaxed?

Check the parking brake setup to make sure is not too tight and is causing the binding.

PackardBob:

When you say "first one wheel, then another, then another..." does that include both front and back, left and right?

Also did any of the tubing get crushed or kinked during or after replacement or any chance something such a cleaning solvent or dirty fluid contaminated the new brake fluid and after the 100 miles and the sit damaged rubber components or hoses are causing the problem.

Also, I would check to make sure pedal clearance to the master cylinder is correct.

Assuming your brake shoes are clean and the cylinders are not leaking, lets start over with the brake adjustment. I abandoned the factory method many years ago and use this with excellent results on all the cars that have hydraulic brakes and the eccentric adjustment at the top of the backing plate. It only take a few minutes per wheel.

Disconnect the e- brake cables at the equalizer. Make certain they are free in their sheaths.

At each wheel: back off the star wheel adjustment quite a bit, say 20-30 clicks. The wheels should turn quite freely.

Loosen the big nut at the top of the backing plate a turn or two. This is the eccentric adjustment which will center up the shoes within the drum. The adjusting screw should start out with the slot vertical and with the higher half of the screw shank (feel it with your finger) toward the rear of the car.

Now tighten up the star wheel adjustment till the drum is dragging heavily. Rotate the eccentric adjustment a little to the front or to the rear to minimize drag. You may have to retighten the star wheel adjustment to bring back the drag. Repeat the process till you have found the position of the eccentric screw where rotation in either direction increases the drag. This means the shoes are nicely centered in the drum. Tighten the lock nut then loosen the star wheel adjustment till the shoes are only just touching the drum. That wheel is done; go do the other three.

After that, pull all of the slack out of the e-brake cables and clamp them in that position with small vice grips or other means. Adjust the cable ends so you can just slide in the retaining pins into the equalizer.

No leakage anywhere related to the brakes. Brake pedal clearance seems to be ok. Followed the instructions in the manual for setting up the brakes. The only thing that seems to be out of the ordinary is the clearance between the brake shoes and brake drum. If you place a feeler gage in there, it seems to be tighter as you go further in. Does that make sense?

This alternate procedure for setting up the brakes looks to be something I should try. Right now I am able to drive the car by slowing down very gradually but would like to be able to drive it more normally and be able to apply more brakes when I have to come to a stop in a shorter distance such as when the light turns yellow or red and I am closing in on the intersection. Not wise to just drive right though and chance an accident.

Is it common to have the 37 Packard 120 brakes lock up or is it just my car?

I appreciate the help because I would like to drive it but am reluctant to do so until I am confident I have the issue resolved.

Thanks,
Bob

Is it common to have the 37 Packard 120 brakes lock up or is it just my car?


It's a problem with your individual car.

Rear Ross's post above. If the problem is only occurring in the rear brakes, then the parking brake being out of adjustment is probably your culprit.