Originally Posted by Blularry
I have an 08 Winnebago Vectra 40TD. I have no problem with the air psi filling quickly when I start the coach. However, once I turn off the engine the rear starts to lose pressure right away, almost like I am dumping the system. I have only had the coach for a few months so I'm still learning about Class A's. What should I be looking for underneath? Is this something I can spot myself or should I just take it to a shop? It does maintain the psi while I'm driving. Thanks for the help.
Your coach is an '08, making it around 13 years old. And you don't say what the miles on it are. My point is, being that old, it's possible that your air leaks can come from many, many places. As has been suggested, it's potentially possible you may have a faulty ride height sensor/valve. If you're not familiar with them, they're a little air control valve that has a lever on it, that attaches to the axle and the frame, close to tires.
Typically, Freightliner installs three of them. In our coach, an '04 Itasca Horizon 36GD with the CAT C-7 330HP, we have one ride height sensor in the rear and two in the front. Why Freightliner did it that way is beyond me but, it is what it is. And, what they do it simple. Based on the adjustment they're set to, they control the "ride height" of the coach, by allowing a given amount of air to the air bags to raise the coach to a set height.
Conversely, they also release air, if the load on the coach is LESS than what it takes to compress the air bags so the adjustment is met. They work constantly to keep the coach at its prescribed height while the coach is operating.
Now, if you're loosing air rapidly, one of the causes could be a faulty ride height sensor. It could also be an air bag or, more than one air bag. It could be fittings in the air lines at valves. It could be pressure protection valves on the tank(s) etc. As has been stated, one must take great care while squirming around under a 15+ ton coach, searching for air leaks. I recently found a massive air leak from one of my front air bags. I replaced all four of them and a pressure protection valve and now my coach will hold air at or around 110-120 for well over 24 hours. I still have a tiny leak somewhere and, when we get done with all our short little trips this summer, I'll be back under there with my little stethoscope to find the culprit.
But, a sprayer with a good solution of soap (dish soap) and water will provide great results of a hissing air leak. Just be careful. If you wanted to keep the coach up while searching for your leak, you can plug in a home air compressor to the front quick release air chuck in the front of the coach. That should sustain your height while searching. Good luck and report back what you find.