VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Brake cylinder kit number please

I adjusted my brakes because I had little pedal on braking. All four wheels took little adjustment so I looked in the master cylinder and it was all but empty of fluid. It seems I have a minor leak somewhere that I'm going to have to diagnose. I'm needing a part number for wheel cylinder kits for the stock '38 car brakes and they master cylinder. My hope is to buy them locally & support home town business. If I need one or more kits I hope to be able to x reference the number to a modern one.

You might be able to just go to Napa and get new pucks for your wheel cylinders. I know in the old days most shops had a kit that had new pucks in it.

Hi Tiny,

I bought wheel cylinder kits for my '37 GB from AutoZone a couple of years ago. Their kits included new pistons which I really needed. Most kits have only the spring and the seals.

You can get the part number by searching their website. They were not it in stock but it only took a day.

Thanks guys. I'm not sure yet what the issue is. I put NOS cylinders on all four corners three years ago. I rebuilt the master cylinder and replaced the flexible lines in '05. Nothing 'should' be leaking but it's obviously losing fluid somewhere. I'll stop by the parts houses next week to see how far back their books go. They usually don't go that far back but often if one has the correct part number they can cross reference to a modern kit. If it turns out to be one of the NOS cylinders I'll order a kit when/if necessary. Thanks again.

Tiny.... Take the wheel cylinders apart first You might find that the only thing they need is new rubber cups in most cases the spring, pistons and every thing else is OK.
The cups can be bough separately at NAPA cheap,THE FRONT AND BACK ARE DIFFERENT SIZES SO LOOK OUT FOR THAT....Those cylinder kits can be expensive and you don't need everything in most cases....Hone the old cylinders ,replace the cups bleed the system and your done.....GOOD LUCK.....ED
BTW...It may be your stop light switch is leaking.

If you are going to keep the car, I strongly urge you to have your master and all wheel cylinders lined with stainless or brass, install new kits, clean all lines and use new fluid, make final adjustments and not worry about brakes for a long time. You will enjoy the peace of mind of knowing you have serviceable brakes when the time comes.

New master cylinder and wheel cylinders will corrode just as fast as old cylinders. Why build a problem?

You can order wheel cylinders by having the bore size which is usually noted on the cylinder.

Hi Tiny,

One more thought about the "missing" brake fluid. You might not have a leak.

Remember that as the brake shoes wear you turn the adjusting cover on the wheel cylinder to extend the adjusting screw. As the screw extends each piston moves further out in the cylinder. This increases the distance between the cups when the brakes are not being applied. The spring between the cups keeps the pistons against the inside end of the adjusting screw.

This greater distance means that more fluid is in each cylinder as you adjust for wear. In these older cars the master cylinder reservoir is not very large so it does not take much wear to displace all that volume.

We don't think about this very much with our modern cars. The reservoir size is much larger in comparison to the volume of fluid that can go into the calipers and wheel cylinders. In fact, you have to be careful when you replace worn out disc brake pads. When you push the piston back into the caliper you can overflow the reservoir if someone added fluid when the pads were half worn.

Just something to consider if you do not find a leak.

The wheel cylinder pistons position is not affected by adjusting the brakes on a 38 chev. Turning the cover to adjust the brakes moves the adjusting screws in & out of the hollow side of the piston. The pistons do not push on the adjusting screws, they push on the outer edge of the covers.

This might be a situation where we are both right. When I rebuilt the wheel cylinders on my '37 I noticed that the brake adjuster screw did push against the center of the piston when the screw was fully retracted.

I agree that after some amount of adjustment then the outer edge of the piston is pushing against the adjusting covers. Once that occurs the volume of fluid in the cylinders is at its maximum except when you apply the brakes.

If you change the fluid every few years you will not have problems with corrosion and leaks. When I bought my 78 Corvette 12 years ago with 17000 miles I asked if he had ever replaced the calipers and he said no, I figured I would have to. When I checked the brakes the right rear was damp. I changed the fluid and have every 2 or 3 years and have not had to change any of the calipers. I am the second owner.