USING SHOP AIR FOR BRAKE INSPECTION?

I've run shop air to my truck (through a regulator set for 120psi) if I have a leak I'm trying to track down...MUCH quieter than running the truck. It also allows you to release the brakes and keep them released without running the truck while servicing the brakes. And yes, as long as the pressure is 90-100, you could check brake stroke and such, too.

The truck doesn't know whether the air came from its own compressor or an outside compressor...just that it has pressure in the system. Unless you're needing to check the truck's compressor, governor, etc...there is no reason why you can't use a shop air supply. Just make sure it's regulated down to 90-130 psi...don't need 155-175 psi pushed into your truck.

 

There are also safety concerns. In very cold weather, it is a lot easier to work in a warm, enclosed area.

Letting a truck engine run to compress air might be a bad idea in some shops without exhaust sleeves to fit on truck exhausts to vent exhaust out of the shop.

Shop air would allow safer testing and service of air systems.

 

Great Question...Good Answers.

Although Shop can help diagnose problems, there are min requirements to consider.

The only way to really inspect an Air System is to make sure every componet from front to back functions according to PART 393—PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION.

(2) Air brake systems. Buses, trucks and truck-tractors equipped with air brake systems and manufactured on or after March 1, 1975, and trailers manufactured on or after January 1, 1975, must, at a minimum, have a service brake system that meets the requirements of FMVSS No. 121 in effect on the date of manufacture. Motor vehicles which were not subject to FMVSS No. 121 on the date of manufacture must have a service brake system that meets the applicable requirements of §§393.42, 393.48, 393.49, 393.51, and 393.52 of this subpart.

§393.40 Required brake systems.
Air brakes for Class A Combination Vehicles

 

You are bypassing components doing it that way. Thats okay to do while it's in the shop but the system should be tested using the foot pedal before driving to be politically correct;
Using the trolley valve to check trailer brakes is not correct either. That's a different system.