Leaky air system

[Paul Schwalen]

Some time ago I posted (with Joel's help) a place where a member could locate a typical layout for the  air systems for a RV.  At that time I mentioned that some time in the future I was going to go under my Contessa and see how it measures up to the typical layout.

The reason I wanted to do that is I have had an annoying air leak ever since we have had this coach and it seems to be getting worse.  The red pointer on the gauge will now drop to zero after about 1.5 hours while the green pointer will stay essentially at where ever it was when I shut down the engine for weeks.  This is a benefit to me because  the air bags are connected to the green pointer and therefore the air bags stay full and the coach will not drop over time when I don't dump the air. (which is the usual case when we are parked at home)

I recently fixed a leak in the 1/2" green hose that exits the Haldex air dryer and goes to the front main tank.  This leak was right at the exit elbow which I had to replace and I thought I had solved my leak problem.  All I found out was I have slowed the leak from a 1 hour drop to a 1.5 hour drop to zero.  have spent an inordinate amout of time under the RV with a paint brush and a cup of Mr. Bubbles soaping up all the connections I can see and have not found any other leaks.

So, the reason for this thread is to ask for help from you guys who have found leaks in hidden places. I can think of the air horns but don't know how to test them. I can't find any way to remove something to let me test for a leak.  (the leak at the air dryer was audible only after I slipped the covering abrasion hose back somewhat and discovered a air noise)  

Up front between the front cap and the dash there are numerous air hose connections but I can't reach most of  them to apply the brush, however I still have pretty good hearing, and cannot detect any air noise coming from that area.

Any suggestions?

[Richard And Babs Ames]

A friend of mine and Diesel mechanic said the best way to find an air leak that is as big as you are describing is to find a very quiet place and listen at night when the air is denser and you can hear small air leaks very well.

[Paul Schwalen]

Thanks for that Richard, I will do that in the next day or so.  We are in Central Florida and the rains come in the evening so I will have to work around them.

It just occured to me that since the green gauge stays up and I just tried the air horn and it works fine with the red gauge at zero that it is not the air horns.  I am very suspicious that the leak is at one of the brake connections and it is difficult to get your ear close to hear, but your idea to try at night may help.

[LarryNCarolynShirk]

You may try a spray bottle to shoot the soapy solution in hard to reach places.

Larry

[Wayne Tull]

I had a leaking brake light switch on my '94 Beaver Marquis. Just something to check if they are similar.

[Larry Fritz]

I have not tried this, but an inexpensive "stethoscope" for auto engines might be a big help in hearing leaks. They have a probe so you can stick them up in those places that your ear cannot reach.

Larry Fritz

[Ken Buck]

Just to make sure someone doesn't misunderstand Larry's idea, the stethescope works very well. Remember you take the bell device off the end and put the open tube end up to areas you suspect are leaking. You will be able to clearly discern where the leak is. For those areas that are hard to reach it will also work with an extension on the tube, say a 3 foot piece of copper tubing.

Another trick I used to use with air tubing which was inside a protective sleeve, (roadranger shift knobs, some brake lines etc.) was to take a small piece of paper about 1/4" wide and a couple inches long and put it up between the coupling and the sleeve whichever way the paper blew told me which end of the line had the leak.

[Paul Schwalen]

Thanks guys for the stethoscope idea.  I will pick one up at the local Harbor Freight and give it a try. It does sound (no pun intended) like a great idea.

Paul

[Larry Fritz]

I have not tried this but an inexpensive "stethoscope" for auto engines might be a big help in hearing leaks. They have a probe so you can stick them up in those places that your ear cannot reach.

Larry Fritz