MRAP Brakes

[Russ Knight]

Our local Sheriff's Department has an MRAP, and the brakes will not release. They've contacted me because they know I have military stuff, and because we work with them on training missions from time to time. They are telling me the air pressure will only build to 118 psi. Where is the adjustment to raise the air pressure and what pressure should it be?

Thanks!

 

[BKubu]

I think the brakes should release well before reaching 118 pounds. The air governor may be on the firewall. Find it on your truck and then send them a picture of it. I am not positive it will look identical, but I wouldn't doubt it either.

 

[Russ Knight]

I think the brakes should release well before reaching 118 pounds. The air governor may be on the firewall. Find it on your truck and then send them a picture of it. I am not positive it will look identical, but I wouldn't doubt it either.

If I remember correctly, there is a sticker on the dash that says something about releasing the brakes and 120psi. I was told this MRAP weighs 80,000 lbs. That might have something to do with it.

 

[juanprado]

As you are probably aware, there are multiple flavors of the mraps out in LEO hands. Would help to know which model?

Brakes not releasing seems to me to a one way check valve or one of the valves in the system as air pressure is sufficient at 118. I would start with the simple things. Check air flow at glad hands, drain air tanks and check for excessive moisture and crud, service air drier? Front or rear or both not releasing? Some of the mraps have disc brakes so another area to check?

 

[simp5782]

Spring brakes release at 60psi

There is a quick release valve that is sticking on the release if they are all still stuck. Or rusted up.

Post a pic of the mrap

 

[Mullaney]

Our local Sheriff's Department has an MRAP, and the brakes will not release. They've contacted me because they know I have military stuff, and because we work with them on training missions from time to time. They are telling me the air pressure will only build to 118 psi. Where is the adjustment to raise the air pressure and what pressure should it be?

Thanks!

.
Might try chocking the wheels and plug "house air into the front (right facing the truck) glad hand if you have it available.
That way if something is hissing air you could track it down rather than trying to hear over the rattle of the motor.

 

[frank8003]

Yeah, photos would help all of Us Help You

 

[Russ Knight]

Well, I don't think it's the brakes. Went out today, started the vehicle, built air, put vehicle in gear, acted like it was in neutral. Cycled ignition off and on a couple of times, put vehicle back in gear, pressed accelerator, vehicle acted like it was straining against the brakes, then a very loud pop and vehicle moved and drove as normal. I know nothing about these things. Couldn't even find valves to purge the air tanks. Pretty sure it has a Freightliner / International engine.

 

[tobyS]

A loud pop may have been frozen pads to disks that let go.....all at once.

 

[Russ Knight]

A loud pop may have been frozen pads to disks that let go.....all at once.

Could be, didn't sound like that though. Not ruling anything out, but when placing the vehicle in gear and pressing the accelerator, it acts like it's in neutral, engine revs freely. But after cycling the power on and off, restarting the vehicle, placing it in gear, pressing accelerator, the vehicle then strained like the brakes were locked, something popped loudly, and the vehicle moved. Seems if the brakes weren't releasing, the engine would not rev freely when placed in gear at any time.

 

[silverstate55]

International MaxxPro... looks like First Gen with solid axles & single rear wheels

 

[Russ Knight]

International MaxxPro... looks like First Gen with solid axles & single rear wheels

Apparently, and electronics out the gazoo.

 

[SWATMOD]

Guessing someone bumped the transfer case into neutral and then put it back to high and it didn't immediately engage, this has been a common occurrence as the TCASE solenoids stick as they don't get used much. This is why its important to regularly use these systems to keep things freed up.

I also get a ton of calls from officers freaking out saying there Maxxpro won't go over 35 mph, I then instruct them to shift the TCASE to high from low.

SWATMOD Tip: Maxxpros must be in N with service brakes applied to shift TCASE from L to H and vise versa.