Truck not building air on idle, everything has been changed!

Hello truckers and mechanics, I’ve been repairing trucks for over 10 years and I’m stumped. Wondering if any ones ran into this problem or can help me out with a idea on what to do next… Freightliner century with a 60 series. Came into the shop not building air past 50 psi. After many trips to the shop, we replaced his air compressor, compressor valve, governor, air dryer, air filter and hoses connecting dryer to compressor. Nothing helps. What could it be?

 

Have you put a gauge on a reservoir to see what’s actually there? Were the brakes on fire when it arrived? 50psi is pretty low to get spring brakes off with. Might be the gauge.

 

Are the tanks full of water / condensation?
Some Freightliners have a two compartment first tank that has a check valve inside between the two halves.

 

Remove the compressor discharge at the compressor and apply shop air to the line and see if you have a massive leak after the air dryer or somewhere else to cause the low pressure. Like mentioned, double check your tanks are actually low. Check your compressor air intake too for being restricted. Hope you find your problem, good luck!

 

Good and interesting way to check things. I have a tire blast can i connect an air line straight to the compressor air outlet. Tank has a gauge on it.

 

I rigged up a fitting with a quick coupler and ball valve that I could thread into the compressor line for that very reason. If shop air is set to more than 120 psi I'd recommend a regulator as well to prevent over-pressurizing the system.

 

Boy are you guys in for a treat and a good laugh! So after checking everything and yes I mean dang near everything, including everything you guys suggested, it was the one place I couldn’t hear from! The VPOD metal line that connects to the turbo actuator had a hole in it from rubbing against the exhaust pipe! A little welding and it builds air up faster then a dolphin about to deep dive! Air only passes through it when the motor is running and due to it being right against the exhaust the leak wasn’t heard till I moved the exhaust in a different repair! Good reminder to check those vpod lines too when u have this issue! Thanks for being a part of this thread guys!