With this issue, we continue with Part 3 of our Bendix  series that started with our 1946 Packard Custom Super 8, then a comparison of Huck and Bendix  brakes as used on Chevrolets (see the Archives section at www.southernwheels.com. In this issue, we will discuss brakes on the 1951 Packard Mayfair.
In 1951, Packard introduced the Mayfair, its first 2-door hardtop, originally intended to be a Juniorlower-priced car, so it was introduced in the 200 Series, as a 250. The price and appointments were closer to the Senior 300 Series, including a 327 straight 8 engine with Ultramatic transmission, toothed grill, leather and vinyl interior, and, by 1952, it was considered a Seniorcar. The Mayfairs beginning as a 200 Series has led to some confusing data on it over the years. The 200 Series had a 288 CID straight 8 and the smaller 1 3/4front and back brake linings, and so did the Mayfair, but according to several sources, the Mayfair got the 2 1/4front brakes in 1952 to help stop the 327. Ours has the 1 3/4and, amazingly, we found NOS linings for it in the original Packard Studebaker box. Our brake problem was that the car pulled hard to the left when the brake pedal was applied. This developed during the period where the car sat for 2 years. At first, to try to remedy this, the brakes were adjusted and bled, but this had no effect on the left-side pull. All four wheels had been rebuilt five years ago, and the rear brakes were working, so we decided to focus on only the fronts.
We put the car securely on the lift, raised the car, removed the hubcaps and tires and removed the front drums and bearings. The seals had been replaced and were not leaking, so we removed them to re-use by taking out the cotter key, leaving the axle nut on loosely and pulling the drum straight off which also pulled the seal straight out. Now we could see what was causing the pulling problem. The shoes were crumbling from rust inside the brake drum. This had formed by letting the car sit. The master cylinder had been replaced two years ago and was not leaking and was supplying Dot-3 fluid to all wheel cylinders.
Basic principles of a hydraulic brake system:
1) The master cylinder supplies the hydraulic force
2) The brake pedal applies the force to the master cylinder and
multiplies the drivers push on the brake pedal
3) The backing plate supports the brake parts at each
wheel and transmits the braking force to the
frame of the car (see the Archives section at
www.southernwheels.com for a detailed
discussion of Bendix  self-servo workings).
4) The brake shoes support the linings and transmit the braking
force to the backing plate.
5) The brake linings and brake drum produce the friction and
convert the power of the moving car into heat.
6) The wheel cylinders actuate and apply the pressure to the brake shoe.
7) The steel tubes and flexible hoses transmit the hydraulic pressure from the master cylinder to each wheel cylinder.
DISASSEMBLY: We always take pictures before taking anything apart, so after taking them, we removed the shoes (always wear safety goggles!). This is done with a brake tool, inserting the cupped end at the anchor pin on the shoe return springs, turning the tool to free the spring from the anchor pin. The shoes were held on by the shoe hold down springs and these are removed by pushing in on them and turning the spring until the hold down pin unlocks from the spring. This leaves the adjuster spring at the bottom holding the shoes together. We usually dont remove this spring, and pull the shoes off with it on, holding the shoes together.
With the brake shoes off, it was a good time to replace the wheel cylinders and hoses while we sent the drums out for turning and arcing to the new brake linings. The 51 brake shoes were originally riveted on. Many of the replacement linings are bonded (glued) on. As we have covered before, we always use old asbestos (soft) linings and we were lucky to have those Packard NOSones.
ASSEMBLY: After everything was cleaned up and painted, wheel wells undercoated, we put everything back together, the primary (short) shoe to the front. We have found it easier to assemble the adjuster and spring, tying the primary and secondary shoes together at the bottom and put this assembly on the backing plate, then the hold down springs by pushing the brake shoes together at the top anchor pin then the guide plate and the pull back springs. A note on the pull back springs: The primary spring is usually not as strong as the secondary spring. The old ones were usually color coded with orange the primary and the yellow the secondary. We tested ours with a scale and found the primary tested at 50 pounds pull and the secondary tested 55 pounds. We also bought some new springs and tested them. All of them were gray and all of them tested at 50 pounds. This was done by using a pull scale and putting one end of the spring in a vise and steadily pulling the other end to a distance that approximated the springs pull in the car. Next, we tried jerking one of the springs and got it to go to a high of 100 pounds, but the spring was stretched way beyond where it would stretch in the drum, so the first test was more accurate. We decided to re-use the old springs. We put a guide plate on the anchor pin, and using the brake tool, pulled each spring on the anchor pin (The orange/yellow code is listed in our 1951-54 approved Packard Service Manual.)
Before installing our brake drums, we re-packed the bearings using a bearing packer with an air grease gun with Valvoline Multi-purpose grease. It is important to use this old-style grease on drum brake cars and the red high temp grease on disc brake cars. Of course, we wore rubber gloves and changed them regularly to keep the grease off of the new linings. Once grease gets into linings, it never really comes out. The lining absorbs the grease all the way through, and although it wipes off with brake cleaner, some is still on the lining. If that happens, we spray brake cleaner on several times, each time wiping down the lining with paper towels. Sometimes it takes 5-6 times.
With everything on the backing plate, we installed the brake drums, outside bearing assembly, the axle washer, nut, tightening down until the wheel barely turns, then backing off to the next cotter pin hole in the axle, then inserted a new cotter pin. We always use high quality, newcotter pins. Then, we installed the grease cups over the axle nuts. We bled the brakes, starting with the farthest wheel cylinder: Right rear, left rear, right front, left front, and bled each wheel until there were no air bubbles coming from the wheel cylinders. We always check the master cylinder after bleeding each wheel, and never let the fluid get below half. The shoes were adjusted by inserting a brake spoon through the slot on the back side of the backing plate. We locked each wheel down, then backed off until the wheel would rotate 1 turn by hand. Packard recommends on the 51-54s that you (on the front side of the drum) insert a .015 feeler gauge through the drum inspection hole between the lining and the drum, about 1 1/2from the lower end of the secondary shoe (4 oclock), expand the adjuster screw (star wheel) until a slight drag is felt on the feeler. Then insert a .010 feeler through the drum inspection hole between the drum and lining about 1 1/2from the upper end of the secondary shoe (1 oclock). If the clearance is not within limits, loosen the anchor pin lock nut and adjust the anchor pin, turning the pin in the direction of the forward wheel rotation to decrease clearance. Turn the anchor pin in the opposite direction to increase clearance. At the same time, re-adjust the adjusting screw to maintain the .015clearance at the lower end of the shoe. Holding the anchor in the set position, tighten the lock nut. Repeat this on all brakes. As a final test, turn the adjusting wheel until the drum can justbe turned with both hands, then back off the adjustment until the drum turns freely a couple of turns. Install brake drum inspection hole covers (front) and adjuster hole cover (back) then put on the wheels. The brake pedal should have 3/4travel. If not, the pedal rod can be adjusted. To adjust, loosen the lock nut on the master cylinder push rod, turn the large hexagon nut into decrease the brake pedal free play and outto increase the brake pedal free play. After the push rod is properly adjusted, tighten down the lock nut. Re-check the brake rod travel while hot. This will be your accurate reading (hot).
Hand Brake Adjustment: (rear wheels only) If it becomes necessary to adjust the hand brake, (with the transmission in neutral),
1) Tighten the adjuster until the wheel can be turned by hand
2) Pull the hand brake lever to the first notch
3) Pull the rear wheel brake cables forward to remove all slack
4) Adjust the clevis of the hand brake cable so that the clevis pin
can be easily installed without any slack in the cable
5) Release the hand brake. Back off the adjuster screw
at each rear wheel.
To equalize: Loosen the tighterbrake. Install the adjuster hole
covers, lower car to the ground.
Now the brakes work greatno pulling! We keep re-learning the same lessonsDont let a car sit! We will see you next month on the 51 Chevy Bendix  complete brake overhaul. Keep em driving!