The Stovebolt Site Forums The Shop Area General Truck Talk 1945 1/2 ton brake problems solved

When I triumphantly announced that my 10 year restoration was finished, a wise member on this forum reminded me that you are never finished. I found out quickly this was true.

I want to chronicle my brake odyssey so that others may learn from my mistakes.

I once read that “sometimes your only purpose in life is to serve as a warning to others.”

Ok, shortly after “finishing” my restoration my brakes began to pump up and not release when I was out driving. From reviewing this board I found out that my relief vent in the master cylinder was not doing its job. This is the hole closest to the firewall with the little hole in the bottom of it. The fix was to remove the master cylinder and clean it thoroughly and to make sure the little vent hole was not plugged. This fix did work.

I put the master cylinder back on the truck but I had a leak from the threaded hole meant for the brake pressure switch. When I bought this master cylinder 10 years ago I plugged the hole with the wrong size bolt and of course it leaked. FYI if you are not using the pressure brake switch, which you should as the mechanical switch will keep your lights on if the brake pedal does not come all the way up, the hole should be plugged with a 1/4’” brass plug like the ones used to plug the windshield wiper vacuum line.

Because of the leak and unreliable nature of the mechanical switch, I bought a new master cylinder and a new pressure switch for the rear brakes lights.

I bench bled the new master cylinder and installed it on the truck. I pumped up the brakes and gave my helper a high five for a job well done. I hit the brakes again and the pedal went straight to the floor. WTH!!!!

I knew that my old master cylinder which I had just removed did work, so I fixed the leak with the above mentioned brass plug and reinstalled the old master cylinder with the old mechanical switch. I pumped up the brakes and high fived my helper for a job well done.I then stepped on the brakes again and the pedal went straight to the floor. WTH!!!!!!

Mad and frustrated that such a simple system was crushing my soul, I decided it must be dirt or something in the master cylinder causing the problem. I took the brand new master cylinder apart in a surgically sterile environment, examined every part cleaned every part and put it back together. I bench bled the master and put it on the truck. At this point I had used about a gallon of dot 3 and I was really getting sick of my truck. I avoided high fiving my helper but the pedal still went straight to the floor.

I decided this was a good time to break up with my truck for awhile. I took a good week of time apart to collect my thoughts and tried to refrain from getting a for sale sign.

Once my head had cleared, I did some research here in the forums and a wise stovebolter said there are two systems used in braking. A hydraulic system and a mechanical system and both must be adjusted properly.

I put the truck on stands, removed the wheels and I adjusted the wheel cylinders until I felt drag and then backed off 4 clicks.

I then pumped up the brakes and OMG, the pedal did not go to the floor and my brakes worked great!!!!

Moral of this long post:
Understand how your braking system works. Thoroughly read your shop manual and understand how the whole system works.
Your truck has a hydraulic and a mechanical component.
Adjust the mechanical end of the system first.
If problem still exists then turn your attention to the hydraulic system.
Remove master cylinder, take apart, inspect and thoroughly clean all components and bench bleed before reinstalling.

My brakes now work great, but then my engine started running like crap.....that will be another post.

................ a lesson well learned is never forgotten....or repeated! Thanks for sharing.

I love this!! I'll have to remember that!

Glad you got your brakes working.

"Nobody is totally worthless- - - - -he can always be a bad example!" One of my coaches in high school used that phrase a lot.

I learned the same lesson on brakes in my early teens- - - - -adjust, then bleed.
Jerry