M2 Brakes & Bags

P51bombay · Apr 18, 2008

2004 M2 w/ air. How well do linings wear and how often do the brakes in general need inspection?

Also, lately I've noticed the air bags are sometimes (but not always) totally collapsed when the truck is parked overnight - doesn't seem to matter if loaded/empty, parking brake set or not. Secondary tank is empty when this happens and even when they don't go flat that tank is frequently lower than the primary. Truck has no trouble maintaining pressue during the day.

Do i have issues?

piper1 · Apr 18, 2008

Not really.

You have a small air leak somewhere on your truck. Suspension systems generally do not use "protected" air, so if something leaks, the bags deflate. As long as you don't pull away without letting the system charge you will be OK. If you want to find the leak, I'd start at the ride height valve considering the age of the truck. Soapy water to find the leak.

Brakes should be inspected for thickness every time the truck is serviced and it should be noted on the work order. That said, if the truck has Q plus style brakes on it (and I'd bet a beer on it), the steer brakes should last 5 to 600k miles and the drives should last at least half that. Brake life depends a lot on the driver and the specs of the brake lining. Once the thickness gets to 3/8 of an inch it time to seriously consider getting them done and soon. 1/4 is the law but with the amount of rust jacking that happens with that de icing goo....

I did it again....simple question, 2000 word answer. D'oh!

P51bombay · Apr 18, 2008

piper1 said:
Not really.

You have a small air leak somewhere on your truck. Suspension systems generally do not use "protected" air, so if something leaks, the bags deflate. As long as you don't pull away without letting the system charge you will be OK. If you want to find the leak, I'd start at the ride height valve considering the age of the truck. Soapy water to find the leak.

Brakes should be inspected for thickness every time the truck is serviced and it should be noted on the work order. That said, if the truck has Q plus style brakes on it (and I'd bet a beer on it), the steer brakes should last 5 to 600k miles and the drives should last at least half that. Brake life depends a lot on the driver and the specs of the brake lining. Once the thickness gets to 3/8 of an inch it time to seriously consider getting them done and soon. 1/4 is the law but with the amount of rust jacking that happens with that de icing goo....

I did it again....simple question, 2000 word answer. D'oh!

LOL - that's ok, more is better. I figured there was a leak somewhere, any idea where to look for the HCV? I'm not particularly hard on brakes but I don't know the condition of them before I got it a year ago. Supposedly "something" was done on the brakes last December but I have no idea what. Plus the owner is kind of a fix it when it breaks type - truck has had virtually nothing done for about 11 months now. Not only that CVSE and local cops are on an inspection kick - although it passed last year without any faults.

piper1 · Apr 18, 2008

HCV should be above the (or one of) rear axle housing. There will be a rod going from the axle housing up to an arm on the valve.

If you feel like rolling under the truck, take a flashlight and look in the slits cut in the dust shields on the brakes. You'll be able to get a good idea what shape things are in.