The Stovebolt Site Forums The Shop Area The HiPo Shop Help! rebuilding 1957 original master cylinder

Does anyone have instructions on how to rebuild master cylinder on 1957 Chevy 3100? I just bought a rebuild kit. Doesn't look complicated but there always seems to be a trick or two that if you know will make it a lot easier. Appreciate any help you can give. Pretty sure this is the problem. Replace brake shoes/wheel cylinder kits front and back on my 3100 57 truck and the pedal has to be pumped to get a good brake, but if you continue to hold it it will finally go to the floor..feels like it is leaking by the seal(it makes driving an adventure )
thanks
ole skool trucks

You definitly need a rebuild on the master cyl. Fluid is bypassing the inner cup. It is easy to do. Take the big nut off the back & remove the snap ring from the front. Disasemble the parts & lay them out as they come out so you can put it back the same way. Hone the cyl. & check for any pits. If the pits wont hone out you need to buy a new cyl. The kit has all new parts except the spring. Put the new check valve on the old spring.e sure & put the thick metal washer back on between the piston & snap ring. You will probably have to remove the clevis from the rod to get the new boot on. This is a good time to clean the threads up good so it will be easy to adjust. Adjust the rod so you have a tiny amount of freeplay before the pedal starts pushing down the piston. There is a small funnel shaped hole in the reservoir with a tiny hole in it. Make sure that hole is open. A piece of tag wire works good. You can put a little silicone grease on the rubber parts or use brake fluid as a lube.Bench bleed the cyl. before you put it on.

The only thing I can add is my experience. I bled the master as well as possible on the bench, then bled it and bled it in the truck. Couldn't get a decent pedal. Let it sit overnight, the master was higher than the wheel cyls, it self bled and had great brakes, so if you're not in a hurry this may work also. I wrench for a living and regularly use gravity bleeding, but this was an extreme case. It worksed, however.

Devin

Thanks 55tractor. I hope to get this done over the weekend. I will remember your trick if I have trouble.

later

Guys I finally had the time to take my master cylinder off of my 57 and rebuild it. The information that I got from you guys really helped. Hardest part of the job was laying on the ground under the truck. Reinstalled the rebuilt unit and got the wife to pump the brakes and didn't take no time and we had a full pedal. Man was I ready to take her down the road. All is well with the brakes again.
Ole skool Trucks

New here and hoping piggy backing someone else's post is okay???
How do you know when you need to replace or rebuild the Master Cylinder? I have a 53 GMC and I can fill the master cylinder at night before I go to bed by the time I wake up my drip pan is full.

Welcome Calhere,
Im kinda new also but welcome to the bolt! I knew mine was bad because when I would get in my truck I would have no brakes (go all the way to the floor), but I could pump them and get a good pedal. If I sat and held it though the pedal would slowly go to the floor. I had an internal leak. The fluid was bypassing the seal and not holding pressure. You have an external leak. It does not necessarily mean you need a rebuild. It depends on were the leak is coming from. It could be from one of the brake lines that attaches to the master cylinder, or it could be leaking from either end of the brake cylinder itself. I would first check to see if you can identify were it is coming from. If it is a line tighten it up. If it is coming from the end of the master cylinder that has the screw cap...tighten the cap. If it is leaking out of the end of the cylinder I would go ahead and rebuild it. The whole rebuild kit was on $23 from Napa. If you click on my link for stovebolt and go to the 2nd page of pictures, you can see my rebuilt master cylinder. Hope this helps. Let me know if you need more info.
later