Problem with the leveling system or air leak, need help please

chessie4905 · August 26, 2015, 06:48:06 AM

Maybe this video can be of some help.

https://www.youtube.com/watch?v=PGFwVLEmhfI

luvrbus · August 26, 2015, 08:23:15 AM

You are going to need to find where the governor is receiving the signal from to unload the compressor,seems to me like it is picking it up from 1 of the tanks that is not airing up air it up with shop air and go from there jmo

bcbusman · August 31, 2015, 06:46:31 PM

No Air signal to the governor, The only air Tank that gets filled is the one for the brakes, no air after that, So I just went and let it go as far the air pressure can go and little over 150 PSI the right front tank protection valve is purging so I know that the air gets up to there and my guess is thats it. Is there a valve between the tanks to let the air go further ? Thank you in advance

Jim Eh. · August 31, 2015, 07:28:26 PM

Do you have a schematic of your air system?

bcbusman · August 31, 2015, 07:55:18 PM

Yes but its a crappy copy, that's why I'm trying to find help on the forum. Maybe someone has a good PDF ( even bought one on ebay in PDF file and still crappy )or anything of the air system on the 79 MC9 that would be great but knowledge is always good too.

thomasinnv · September 01, 2015, 09:29:15 AM

Pressure protection valve

bcbusman · September 01, 2015, 09:44:34 AM

Pressure protection valve is releasing at 150PSI I know that

thomasinnv · September 01, 2015, 04:52:28 PM

You are confusing the pressure protection valve with the pressure relief valve. the pressure protection valve is in line between the wet tank and auxiliary tank. It's purpose is to prevent air from entering the aux tank if the supply pressure is below 65. They do fail, and when they do it can cause the issue you describe.

thomasinnv · September 01, 2015, 04:56:07 PM

I think I suggested that about a week and a half ago, be interested to hear if that turns out to be it. That's where I'd put my money.

bcbusman · September 02, 2015, 12:09:42 AM

Thank you, I will take floor apart and try to get to it tomorrow,

thomasinnv · September 02, 2015, 06:06:16 AM

You shouldn't have to take the floor apart. you should be able to access it from underneath the bus.

bcbusman · September 02, 2015, 02:28:06 PM

I have no place to go under, Is it accessible under the floor ?

thomasinnv · September 02, 2015, 03:41:23 PM

I seriously doubt it. You will need to get under the bus. I can't remember exactly where it's located but it will be between the dry tank and the auxiliary tank. Most likely next to either one, not in the middle. Someone should be able to chime in and tell you where to find it. If I was a betting man that's where I would put my money.

thomasinnv · September 02, 2015, 04:05:14 PM

I gor out my service manual and took a look, I was incorrect. The pressure protection valve is located between the dry tank (located fore of the rear axle), and the tee inline supplying the park brake tank (passenger side above front axle) and the auxiliary tank (under driver). I believe the tee is located on the park brake tank, so the pressure protection valve could be located @ the tee, or less likely in the rear area next to the dry tank. I would start up front and go from there.

Oonrahnjay · September 02, 2015, 04:42:01 PM

Quote from: thomasinnv on September 02, 2015, 04:05:14 PMI gor out my service manual and took a look, I was incorrect. The pressure protection valve is located between the dry tank (located fore of the rear axle), and the tee inline supplying the park brake tank (passenger side above front axle) and the auxiliary tank (under driver). I believe the tee is located on the park brake tank, so the pressure protection valve could be located @ the tee, or less likely in the rear area next to the dry tank. I would start up front and go from there.

This thread has dragged on so long that I can't find details but I think he said that he has air in the dry tank but nowhere else. This info on the location of the pressure protection valve pretty much nails it. Thanks, Thomas.