15 Oct What Would Cause Brakes to not Release?

Posted at 12:23h in Truck Repair Tips by

The first thing to do is walk around and check to see if you can hear an air leak. If you notice a leak see if it’s coming from a valve or a brake can. If it’s a valve trace the lines back to the brake can, do they go to the forward ports or the rear ones?

If it goes to the forward ports, remove the lines from the forward ports on both cans, is there air coming out of one of the brake cans? If there is that can will have to be replaced. Sometimes it will make your yellow knob in the cab leak too when you have a brake can leaking.

If the cans aren’t leaking from the forward ports and the valve is still leaking replace the valve. If the line goes to the rear brake can ports, replace the valve. If you have a leak at the rear of the cab or rear frame you may a tractor protection valve (TP) leaking. The most common TP valves are the TP-3 and TP-5.

If you have no leaks, leave the yellow knob out and remove the rear lines from the brake cans, block the wheels and push in the yellow knob with more than 60 psi on the air system and check for air coming out of the brake hoses.

If there’s no air, remove the supply line from the emergency supply valve is there air to that valve? If yes replace the valve, if no you have a blockage from the gladhands to the valve. Remember to always plug or dummy couple your gladhands when your hoses and trailer are unhooked. Keeps debris out of the air system.

If all components seem to be functioning you may have a stuck s-cam from brakes that are ready to cam over or lack of grease. Bent brackets that prevent free movement of brake components. If you’ve been driving in snow and stopped and applied your brakes, they will be frozen to the drums.

You will have to properly block your wheels or secure your truck to another truck of equal size for the load and incline, (personal injury or death could occur when brake pops and truck is not held by another device)

Then take a dead blow or other soft hammer and hit the metal part of the brake shoe to get them to pop from the drum, remember to have your yellow button pushed in. The wheel should pop or the shoe should jump when it breaks free. Sometimes you may have to hit the drum as well if it freezes at the top. Most of the time it freezes at the bottom.