Community Forums

mrbodywork · 11-21-2013, 02:55 PM

Hello Folks,

Once again I defer to the wisdom of the collective.

I am having an air brake issue I can't wrap my head around. I spent some time researching but haven't found the situation listed in the forums.

Over the last 6 months my coach has been slowly losing pressure when parked. I have had the coach since 2010 and in the beginning the air pressure stayed wherever it was when parked for extended periods with no noticeable drop. Recently it has been dropping down low enough that the low air buzzer sounds for the first couple minutes when we start the coach. It then airs up to its full 130 lbs, purges and all is good. Perhaps because I have been paying more attention but during a trip this past weekend I watched the air pressure the whole trip.

Now while driving at cruise at 62 mph, the coach will lose air down to the cut in pressure of 105 lbs in approx. 11 min. I repeatedly timed this on my trip home. It is both tanks dropping equally.

I immediately did a full air brake test and listened for escaping air. The air brake test passed and I can hear no escaping air. I will be bringing the coach in for service next week but I wanted to try to diagnose the problem in advance.

I was thinking this could be an air bag issue but wouldn't that just affect the tank supplying that airbag? Someone else suggested the emergency brake actuator may be leaking.

For those of you who have gone through the soap and spray search for air leaks, how did you get under the coach safely without a pit or lift. I'm not huge but it appears to be a tight squeeze or maybe its just my claustrophobia.

Thanks in advance for the help.

Bill

94-Newmar · 11-21-2013, 04:51 PM

Bill, air leaks can be anywhere unfortunately as you're finding out. The treadle, each air spring, numerous valves, regulators etc. The only way to really find it is to let it air up, set your leveling jacks and shut it off, grab a creeper and start rolling around underneath. Hopefully you're in an area with very little ambient noise such as freeways or busy highways so you can hear where it might be leaking from as it's probably a very quiet leak. Once you've determined about where you think it is then you can start spraying soapy water all around the lines in that area. Good luck.

BFlinn181 · 11-21-2013, 05:13 PM

Creative parking, putting one side on blocks or the curb, straddling a ditch, etc. can give you enough clearance to get underneath. I prefer sheets of cardboard to slide on, it's lower than a creeper.

DtBt · 11-21-2013, 05:43 PM

What you describe is not that unusual. As you go down the road the air suspension releases air as it reacts to the road surface changes. Some usual suspects for small air leaks include:
step cover Mac valve or cylinder ( if step cover not electric)
leveler valves - one in front- two in rear
Parking brake valve (on side console)

TBS-POPS · 11-21-2013, 07:42 PM

Stethoscope will do wonders finding an air leak along with the bottle of soapy water. water on fittings, stethoscope on valves for the internal leaks...good luck!

Mac99 · 11-21-2013, 08:40 PM

Sounds normal to me, I have a Freightliner chassis. When parked for a week or so the pressure will
drop below 65 and the alarm will sound at start
up for a minute or so. These systems are not
airtight, leaks are normal. This is what the experts
have told me.

MSHappyCampers · 11-22-2013, 09:03 AM

Bill, my Windsor loses air when it is parked for an extended period. When I start the engine I usually have to wait several minutes for the air to build up to the bleed-off point of 125 PSI. I've never noticed the air dropping back down when I'm on the road, but not sure about that. I just thought this was normal since mine levels using the air bags and automatically keeps re-adjusting the bags if the leveling gets off a bit. I'll watch this thread to see what your outcome is! Good luck!

BTW- I would not get under that monster without a good set of jack stands! I bought a set of the 12-ton jack stands from Harbor Freight. I raise the air bags all the way up to get maximum clearance, then put the jack stand under there.

HVAC Bill · 11-22-2013, 09:35 AM

Pneumatic leaks are not uncommon and can be very time consuming to locate, with that being said, you can expect repair shops to except small leaks instead of locating and repairing as they try to do with air conditioning leaks. I personally expect a tight air system and would suggest you start at the compressor and work your way out bubble testing all connectors and possible spots the plastic tubing could rub thru. Like I said, time consuming. Bill