Packard Forum Index » V-8 (1955-56)

The brake system on the ’55 Caribbean has been completely rebuilt (Treadlevac rebuilt, new wheel cylinders, shoes relined, flexible hoses replaced, system flushed, fresh fluid added [DOT 3], wheel bearings and seals installed, and drums replaced or turned [keeping them with less than 0.06” oversize].). Driving around the area they respond very nice. However, on a 50 mile drive with some stop and go they felted like there was some brake fade and when the pedal was hard there was a chattering, grabbing and groaning noise from the front wheels.

It seems to me that the problem is due to overheating of the front brake shoes and drums. Is there any else that the problem can be associated with?

Don't know about the noise but there have been some articles saying most newer brake linings are softer and somewhat more sensitive to fade than the older asbestos type. If that is correct there could be a heat build up issue with the old brake drums where ventilation was not something they worried about or at least was not very well implemented. Another consideration if the shoes were not arced is the linings could be making contact on a relatively small area which could make any fade caused by heat build up issues worse.

Check the adjustments to make sure they are not unduly dragging and causing a heat build-up. There is an eccentric in the backing plate that is used to align the brake shoes to the drum. That adjustment is missed a lot when folks replace brakes. I think it's referred to as the major adjustment in the service manual.

As Howard pointed out, if the shoes were not arched to the drum, then that could cause issues as well. Perhaps get the front end up in the air with the car running and work the brakes a few times and make sure the wheel still spins with just a hair of drag. Any more and that could be an issue. Someone before reported that BTV was holding too much residual pressure when off the brakes and causing excessive drag running. But I let someone else with more knowledge chime in on that.

I believe the eccentric stopped being included after 54 but don't quote me on that

Reading the manual I didn't see any mention of an eccentric. Both wheels are free wheeling so I have eliminated shoe drag on the drums. Pressing the brake wheel (engine running) they remained free wheeling so the vacuum system shouldn't be an issue.

You probably don't have them adjusted tight enough. The shoes should lightly drag when they are adjusted properly. You spin the wheel in the forward direction of road travel by hand while tightening the adjuster until the wheel becomes hard to turn. It'll just about lock up suddenly. Then you back off the adjuster a few notches to get a light drag.

These are big brakes. They stop quite well when they are operating correctly.

You don't want any drag. That's in the manual. If there is slight drag at room temperature you will have heavy drag at lower temperatures. I would pull the shoes and lay them in the drums to verify concentricity. Lack of will require shimming or thicker lining material.

As for braking in general there have been discussions about fade, but I refer to the Jay Leno article on junktube where he talks about his Caribbean losing brakes on Mulholland Drive.

Ross has utube video on brake adjustment
youtube.com/watch?v=T1Zc3aW18Z4

Is there an adjustment for brake pedal free play on the Easamatic equipped cars so the piston in the master cylinder will fully retract? A piston which does not fully retract will cause brake fluid pressure to build and be applied to the system causing the brake shoes to expand and overheat.

There is no adjustment because the operating rod is attached directly to the pedal. All you can do externally is ensure the pedal is not binding or mechanically cannot move full distance.

Return is done by a heavy internal spring that pushes the hydraulic and vacuum power piston back. It needs to be in good condition and properly seated behind the retainer and clip. Lube on the vacuum cylinder side walls and leather piston cup can not have become so gummy or thick that the piston will not move freely.

If fluid is leaking past the hydraulic seal and the relief port is blocked it can accumulate in the vacuum side and become very sticky. Anything with the spring, lube, or fluid accumulation requires disassembly to check because they are behind the power piston and cannot be seen.

Assuming items behind the power piston are all OK the only other things inside the unit that would prevent full travel and need checking is to make sure the internal vacuum hose has not twisted out of place or the felt cushion pad at the upper side of the power piston is not dislodged or so thick that the piston cannot travel the full distance to rest against the lid. Those items can be checked by only removing the lid.

The residual check valve is a unit assembly and calibrated to a specific psi. Don't remember the number offhand but it is conceivable a contaminated fluid could have swelled the rubber inside the valve unit and knocked the calibration out of whack.