Community Forums

94-Newmar · 01-02-2010, 04:55 AM

Spartan Chassis/Cummins 8.3C/3060

MH has been parked for a month or so but needed to move it to the side of the garage so I started it up yesterday brought temps and up. Air built to 130 or so in each tank. As always I hit the brakes a couple of times before releasing the parking brake. When I let off the brake I can hear a huge hissing sound near one of the tanks up front. The gauge for the rear air goes starts declining fast then at about 80lbs the front tank starts emptying too. Both tanks emptied in less than 20 seconds. So I shut the engine off and restarted it and the air builds right back up. But as soon as I hit the brakes once or twice and release the same thing happens. Since it will build pressure back up it doesn't sound like a cracked line to me. Valve of some sort perhaps?

I'll crawl under today with a bottle of soapy water to try to find the leak. I know its not in the treadle/pedal valve - its over on the passenger side up front where both my tanks are. Its not near either of the wheels, its definitely way up front near both tanks. In the meantime - does anyone have any ideas what might be wrong? It is only 17 degrees here.. perhaps a valve or something has frozen? Can they freeze? I religiously check my tank drains for water and just before I winterized the MH I did open the bleeders on the tanks to make sure there was no water in them - which there wasn't.

Thanks in Advance.

D.
==============

Jim Stewart · 01-02-2010, 06:43 AM

If it bleeds and then airs up when restarted and only escapes when you hit the brakes, how about the air dump switch? I beleive that it is acting just like you are hitting the dump switch with one tank first and then the second.

94-Newmar · 01-02-2010, 09:01 AM

Ok, a bit more info now. With both tanks up to ~120psi or so I shut off the engine. Walk around cant hear any leaks. Hit the brakes a couple of times and air starts rushing out from the passenger side rear brake assembly. (the sound I was hearing up front was the air escaping the tank, not any leaks up front) Interestingly enough, as the air is escaping if I push on the brake realllllly hard the leaking stops until I just lift a little bit then it starts escaping out again and wont stop until I push really hard on the brake again. Is this a bad air cylinder/assembly back there? Perhaps referred to as the actuator?

94-Newmar · 01-02-2010, 12:28 PM

I found the issue. Appears to be a quick release valve mounted on the frame near the rear axle which supplies both rear air brake assemblies. This valve is sticking periodically quickly emptying both tanks. The protective rubber stopper on the front is obviously degraded so its probably letting water and various pieces of junk in it which probably caused the valve to get sticky... I'll get on it.

GaryKD · 01-02-2010, 12:57 PM

Hi 94-Newmar,

You are a brave fella to be out in the cold crawling around under your coach. You are my hero.

Weather outside what the coach usually operates in can cause many new adventures. Normally I advise doing nothing until the weather the coach normally operates in returns and then see if the failure remains. However, the failing device may be on it's last legs. A failure by this device, while on the road, is a coach stopper. It might be best to replace the device before the summer traveling season.

94-Newmar · 01-02-2010, 01:06 PM

Yea we use ours year round. Kinda need to replace it now - need to use the RV later this week. This is either a quick release or a service relay valve.. not sure how they're identifying it. It is a rebuildable item as you can barely see the inside snap-ring near the base of the plunger. I'm going to pull that apart first and see if I can find a rebuild kit for it Monday - otherwise changing the entire thing out is going to be time consuming since none of the supply air lines are quick disconnects :(