Tech Tip of the day Parking brake not activating

[scottmandu]

If your parking brake is not activating, the check valve located behind the front bumper under the emergency glad hand may be bad. This check valve sends air to the emergency air chambers, from the vehicle's air source or the pulling vehicles air source through the emergency glad hand. I've learned this after spending about 6 hours tracing down every line in the parking brake circuit. The valve can be overhauled. The repair kit is about $15 and the valve itself is $35

 

[NDT]

This same valve is also bad if you are unable to charge the vehicle's air system through the front emergency glad hand.

 

[Adventure Driven]

Do you use the red gladhand to charge the system? I would love to have a way to do this as my truck smells up the garage so much until the tanks fill

Seth

This same valve is also bad if you are unable to charge the vehicle's air system through the front emergency glad hand.

 

[Swamp Donkey]

Looks like a KN23000 (or equivalent) one-way check valve. The whole valve is like $13 at TruckPro without an account. Appears to be the same as the ones on the M939 trucks. Very common part on civilian trucks and should be in stock.

 

[scottmandu]

This same valve is also bad if you are unable to charge the vehicle's air system through the front emergency glad hand.

If I remember if the valve is stuck open, your parking brake won't work, and if it's stuck closed you can't charge the emergency system through the front gladhand.

 

[Suprman]

The problem comes into play when your valve is stuck open from the last guy charging the air system from the front reg gladhand. Then the next guy cant build air since the valve is now stuck open. So they plug up the front reg gladhand to build air. Which feeds air back into the spring brake release circuit intended for towing.

 

[DCLund]

The red glad hand can be used to charge the truck air but be aware that the Parking brake will release as it charges. Always use wheel chocks.

Dane