M923A2 shutoff sounds

[Suprman]

When I engage the park brake and shut off my M923A2 I get a loud groan it sounds like air releasing. It is not the same as the ctis blowoff sound when the system decides the tires are at pressure. Is this sound normal everything seems to be working as it should
Thanks
Will

 

[chadande]

When I engage the park brake and shut off my M923A2 I get a loud groan it sounds like air releasing. It is not the same as the ctis blowoff sound when the system decides the tires are at pressure. Is this sound normal everything seems to be working as it should
Thanks
Will

Does it come from the CTIS manifold down near the front floor of the cab or elsewhere?

 

[dogtags]

Sounds like the normal sound of air from the application of the parking brake exhausting out the air intake. Do you hear the same noise when you apply the parking brake while the truck is running and you have you head outside the driver's door near the intake?

 

[jcappeljr]

Mine does the same.

 

[Suprman]

It is definitely related to the parking brake application.

 

[wreckerman893]

It happens on all the 5 ton 900 series truck. Just the nature of the beast.