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I would probably just replace the piggyback assembly if the emergency brake side went bad. You could have an accident even doing the service side, but the emergency park spring is completely contained in the rear piggyback section so it's safer than trying to replace the diaphragm on the...

I replaced the service side diaphragm and not the park/emergency side. The park/emergency side canister remains together, with the spring caged for the service side replacement.

I did have a leak from that same vent, but it wasn't a huge leak. Mine turned out to be one of those 3 two-way check valves behind the driver's side step. If you have already replaced yours it could be something else. How long ago did you replace them? It could be worth a sanity check to take...

The park valve will not stay depressed unless you have adequate air pressure. It works as a fail safe in that regard. Pressure drops and the valve pops. The valve might be fine and the problem just that you can't build enough pressure in the system. How much pressure do the front and rear brake...

My truck finally developed another air brake leak. This time when applying the service brakes (pedal) air was exhausting from the front Service gladhand. The harder I pressed the pedal, the more air escaped. As you can imagine the truck would quickly lose air pressure. The problem was once again...

The park brake dash valve is a Haldex KN20035. The trailer dash valve is a Haldex KN20025. On these first generation trucks those two valves are separate. On newer trucks they are integrated into a single valve assembly which is also serviceable. Maybe one day I will swap out the two...

I had a couple leaky air tank drain valves. I replaced those with Tectran 110, stock number 90076. They look almost identical and seal very well.

Now for the tractor protection valve. My truck developed another leak at the rear of the truck that I was able to trace to the tractor protection valve. On the top of the valve there is a bleeder, and when applying the service brakes (pedal) it would dump air out of there. The harder I pushed...

The brakes on these trucks are wedge brakes. One of the guys at the local Truck Pro commented that wedge brakes are obsolete now with other self-adjusting brake systems. He asked if the truck was really old and was surprised when I told him mine was a 93 model. If you are completely new to...

I wanted to share some of the information I have learned about the LMTV / FMTV air brake system. I encourage you to also share the tips/tricks/etc you have found. Please do not post troubleshooting questions in this thread, let's keep this one for sharing solutions. If you are actively...