The Stovebolt Site Forums The Shop Area Engine Shop New truck to me, but brake problems.....

Ok, I bought this sweet 1952 GMC 1/2 ton, all stock, in very nice condition, I am driving here and there to get a good feel for everything and to just "shake down" the truck.

All new brake components were installed 3 years ago, all stock. After driving truck for a while the brake pedel gets real hard and will not travel at all and before you know it all of the brakes are fully locked up. At first when this happeded I checked the brake fuild and there was barely any in the master cylinder. I know, should have known better to check this before driving/purchase but I got so excited I forgot. So, I added fluid and the brakes looseneed up and I was back in business. In the back of my mind I'm thinking I better bleed these brakes and re-fill the fluid to makes things right. Well, I have not had time to bleed the brakes but after dinner this truck kept calling me out for a drive, so I went for a little cruise and sure enough the brake pedal got hard with no travel and the brakes locked up again. This time when I checked the fluid it was full, but very murky in color and I could not see through it. I un-hooked the brake linkage to the pedal so all is good there, it must be a pressure/fluid/air problem. No leaks anywhere in the brake system.

I'm thinking there must be air or debri in the system, and a full brake system fluid flush is in order and then bleed brakes as per service manual. I am just looking for advice/opinion, and or has anyone else here had this happen?

Thanks in advance, and I will post pictures of this fine truck very soon.

If it occurs on all wheels, it is the master cylinder getting blocked from junk in the master cylinder return port (you mentioned that the linkage is now disconnected so that rules out the lack of free-play clearance).
If it is one of the front brake flex lines, or the rear brake flex line it would not make the pedal get hard...

"I un-hooked the brake linkage to the pedal so all is good there"..

Phillip, Try backing off on the adjustment rod from the inside of the master cylinder to the linkage and see what happens..

Also, you say you think there are no leaks in the system. Did you pull all the wheels and look behind the dust covers of the wheel cylinders ? Those cylinders can leak a lot of fluid before it shows up on the inside of the backing plate.. When you first checked the brake fluid you said it was low, it had to go somewhere..

Murky fluid can mean rusty lines. Are the brake lines new or old ?

Keep us posted..

Definitely a clogged port in the master cylinder. The fluid was low because it is trapped in the lines. This is causing the pedal to be hard and the brakes to lock down. It is just like having the brakes to the floor. If it were my truck, I would take the opportunity to upgrade to a dual master cylinder and replace all lines (it sounds like they are rusted or gummed up) including the rubber hoses at each wheel. Brakes are nothing to be guessing about. I don't know which is more dangerous, no brakes or locked down brakes. Good luck

Phil

Thanks guys for all of the imput!!! I have not checked the wheel cylinders themselves for leaks, but only because my garage at the house is so small I can barely walk around my truck once it is parked in there. I was hoping that low fluid was due to the prior owner not filling the system/bleeding the brakes properly 3 years ago when he did all of the brake work.

I will take the truck to work and put it up on the lift and then pull the drums and check the dust caps on the wheel cylinders and then go from there. I have a second master cylinder lined up just in case. I will also flush out the brake fluid and re-fill and then bleed the brakes.

Thanks for all of the advice/tips. This website is great and I look forward to posting some positve news about the brakes real soon.

I also bought a 52 about 7 yrs ago and when I bought it,, suspose to have all new brakes,,,,after they locked up and pull like crazy I found out that someone told a lie,,redone the whole brakes sysem, no problems since,,,,,good luck with yours.....Fred

Guys;

This truck has new: brake shoes, wheel cylinders, brake hoses, brake lines, and rebuilt master cylinder, per the owner and his receipts to prove it. The only problem I see is he kept this truck in garage for three years after his restoration and has only put around 200 miles on the truck. As everyone here knows it is very bad for a truck to sit like that. I hope that this gets worked out soon, It is just driving me crazy having this nice truck sit in my garage with brake problems.

UPDATE!! UPDATE!!

All is well in the Pierce Garage. Yesterday, I headed off to the shop for a more in depth brake system check over. The weather here is perfect, high's of 75, sunny, no rain in sight. After driving the truck to the shop the brakes started to lock up. Once I was on the lift, all four wheels would not spin. I released some pressure fromt the right rear wheel cylinder, and alot of fluid came out, hence alot of pressure. So, I pulled the drums, all looked good, wheel cylinders, hardware, ect. No leaks. I checked all adjustments, i.e, brake pedal/toe board clearance, and brake shoe to drum clearance, which was fine. I decided to pull the master cyliner and it looked ok, but inside it was grimey and there was some debri. I intalled a new master cylinder, and then bled the brake system, twice, and now the brakes are AWESOME!! Maybe the return port was clogged and it would not let fluid return to the master cylinder from the wheel cylinders. This truck brakes so good now, amd I am very happy!!

While I was in the shop, I went ahead and replaced the fuel pump, as it was leaking, and Mrs. Pierce doesn't like the smell of gas in the garage. I installed a passenger mirror, and running board steps. I had a extra floor board muffler heat sheild, I put that on, then spent the rest of the day cleaning, cleaning, and oh, more cleaning of the truck. Today we are going to head out to take some nice photos with the truck, so I will post them tonight!! HAVE A GREAT SUNDAY EVERYBODY!!!!!