Rattle while starting to air up.

[johns4104s]

After being stopped over night and then starting up, MCI 9 has a funny sound from around the front air tanks, it sounds like rattling .It goes away when we are fully aired up. Any ideas?

Thanks

John

[gomer]

I think that the check valve in the tank is the varmit

Gomer

[gus]

I agree with Gomer. Although I'm a GMC man I think it is probably the check valve that keeps brake air out of the aux air system until there is enough pressure to safely apply the brakes.

[johns4104s]

Thanks Guys,

I am in the middle of a 5000 mile  trip, how urgent do you think it is to change it? Can it wait till I get home and get it over the pit?

I very much appreciate your input.

John

[buswarrior]

Don't worry about it.

As long as things are normal while operating...

It is good preventive maintenance to work through a progression of changing out ALL air system components. Check valves and pressure protection valves especially, since no one knows how to check them, and you can be sure they weren't/aren't for proper function.

Not on the DOT list.

happy coaching!
buswarrior

[gus]

My 4104 check valve leaked for a year or two but it never holds much air overnight anyway. The engine always needs to be warmed up anyway and actually warms up better if it is under a small load like the compressor.

I finally repaired the valve when doing other work on the air system.

As long as the suspension holds air overnight or longer that is what counts to me because it takes much longer to fill.

The brake system fills pretty quickly, the check valve is there to keep the air in those tanks and to keep main pressure from loading the compressor when it starts. It may make your compressor work a bit more but it all depends on how fast it leaks the air out of the two main tanks.