I have a F 800 5.9 Diesel. The fuel pump is on the left side on engine. vin # is 3FEXF80C8SJA00679. The unite has 100,00 miles The air pressure will not build up to 120 psi. A new Brake Gov D2 bendex was put on by my mechanic . When using brakes, pressure will drop and will not build up. Was told the brake cams are rolled over. I dont have a manual or i would try to fix the problem myself. The shop wants 100.00 bucks an hr. plus parts. Do you think this is a job I could do with no experience. Thanks
I don't claim to be an air brake expert by any means, but what little I do know the brakes being over cam shouldn't cause the air pressure problem. In fact, if they were over cam, the brakes wouldn't work. You've stated that if you use the brakes, the air wont build up. If this is the case, you'd eventually have 0 air pressure. You're going to have to elaborate a little more on what the problem is. You should be able to find an exploded diagram of your brakes somewhere on line. If you have mechanical skills you should be able to service them yourself, I've done them on my truck. A word of caution: Make sure you get the tool used to lock the maxi brakes in place before working on the air chambers. They are under extreme spring pressure and will certainly cause injury if not worse if you try to work on them without securing them.
Thanks for your reply. At start up. Pressure is slow to climb to 120psi. Once at 120 and button is in and brakes are used pressure will drop as low as 60 psi. Pump is not bringing pressure up to 120. Its very very slow to build up pressure. It just cant build pressure fast enough to keep up with brake usage. Thanks
Could be several reasons for this,,,, 1) Your air compressor could be worn out (a good sign of this is alot of oil in your air tanks) 2) you have a diaphram (pancake) with a hole in it in one of your brake canisters. 3) If the unit has an air dryer on it, that could need servicing, and on an on... First thing I would do is get a helper to listen for air leaks for you, air the truck up, shut it off with the park brake released, step and hold the brake down and have your helper listen for air leak.... would be a good idea to have the trucks wheels chocked up..... After that test let us know what you've found. Gramps.
And does your system have a dryer?
I've seen carbon buildup,from cooked motor oil, in the end of the air line from high mileage air compressors. It can build up until it starts to block the air flow. Follow the air line off the back of the compressor down to the air tank, it should connect to a check valve mounted on the end of the tank. Undo the air line and start the engine. See if there is a reasonable amount of air,under pressure, coming out.
I'm with Mike. A plugged compressor output line. Remove the entire line, and inspect internally. Run a long wire through it, blow air through it, snake through, anything to ensure no blockage. Or, simply replace it.
Thanks Guys for your input. This is where i am with the brake problem. R-Brake pod was leaking externally. L-pod is back feeding through re valve. The shop replaced both pods. cost $404.00 I paid up rather than do the job myself. A pin hole was found in r-air tank. I will repair that after the rain stops. Driving home the air stayed at 120. Thats what i needed. I now have $6000.00 in this F800 175 hp Diesel single axle Dump with 101,000 miles. Steve Frazier, I am told the L-rear brake is Cammed Over. So that means, that break is no t working? right? I am about ready to make a haul to see if if this truck will pull and stop. Thanks Again Elvis
Below is a diagram of a typical air brake assembly. If the brake linings or brake drum are worn too much it will allow the cam to travel beyond its design capacity and go "over cam". The cam followers become trapped behind the S-cam and can not retract. That brake is no longer functioning and in some cases cause the brake to drag on that wheel.
And I would add that if it is "over cam", the brake shoes and/or drum are worn slap out requiring replacement. And if that shoe/drum set is worn out, good likelihood the other shoes/drums aren't much better.