Not Fast Idle afterall

rv_safetyman · February 19, 2011, 06:48:24 PM

Rich, as noted in the other thread: *****BE SURE TO BLOCK UP THE BUS BEFORE YOU CRAWL UNDER IT******

I don't know my MCIs all that well, but I wonder if your model has the air beam construction (not even sure if they used it on rear suspension). If you do have the air beam, then it could be the air beam and not the bag that is leaking.

If all of that is correct, you have a pretty serious decision to make. If the air beam is leaking you will have to plate it. Then the decision: do I put the convoluted air bag back on or convert to a rolling diaphragm type air bag. Sorry, lots of assumptions here, but the folks who know will verify if it is an air beam application.

As far as isolating the air bag, every air bag inlet I have seen is pipe thread. See if you can unscrew the supply hose at the air bag and cap it off. That will allow you to isolate the one location.

If it is indeed the air bag, I would inspect it closely for signs of aging vs damage. If it is aging/fatigue (lots of tiny cracks), I would be very careful to check the other bags for the same condition. Better to change them now when you have the time and resources. I don't know about convoluted air bags, but rolling diaphragm type used to go for around $100 a few years ago. Not all the bad considering that Mr. Murphy would dictate a failure in the worst possible geographical location.

Jim

Highway Yacht · February 19, 2011, 10:04:42 PM

Not trying to Hijack Rich's thread here but since the safety Issue of blocking up his bus was brought up, where do you guys safely block up the body of the bus? I imagine once the air pressure drops and the bags start to deflate, that is a lot of weight resting on those blocks. Do you just block it up under one of the bay floors? I know on my MC-9 there doesn't seem to be any serious bracking under there and and I wasn't sure the bay floor could handle the weight of the bus without bending once the air bags deflated.

bevans6 · February 20, 2011, 04:25:06 AM

I block the bus at the body jacking points. there is a big enough strong point in the frame to jack up the bus and get blocking beside it.

Brian

coloradorich · February 20, 2011, 09:14:54 AM

I do have air beams, but I could see around the drive wheels the actual leak on the airbag. Will try to isolate the airbag to check for other leaks but may have to wait until the bus is blocked and the tires are removed.

Rich

Oonrahnjay · February 20, 2011, 11:24:39 AM

Quote from: coloradorich on February 20, 2011, 09:14:54 AM(snip) Will try to isolate the airbag to check for other leaks (snip)

Rich, an easy, cheap, often-readily-available way to seal off an air line is a simple 3-way or T-connector with the correct female threads (almost always NPT, National Pipe Thread, on my bus). Take your air line with the threaded end fitting, screw it into the T-connector and put plain plugs into the other two holes. That isolates the components that you know are leaking and the parts can be obtained at most local hardware stores. If your airline is terminated in a female fitting (rare but not unknown), you can buy a T-connector that has one male fitting and two females, or you can buy a male-male double-ended nipple that will join a female-threaded T-connector to a female end fitting.

I carry lots of these little pieces in sizes to match the pipe threads on my bus. Very useful, indeed.

Oonrahnjay · February 20, 2011, 12:38:07 PM

Here's a very simplified sketch of what i was trying to explain above:

The left side shows an air line going to an air bag fitting. The center sketch is of a male fitting on the end of the air line; air line is disconnected from the bag fixture and capped by a plain T-fitting with plugs. The right side show a female connector on the end of the air line (I don't think this is common but possible -- but this illustrates the utility of plain, inexpensive brass fittings).

brando4905 · February 20, 2011, 12:51:57 PM

Bruce,

Is there any reason why you couldn't just use a brass cap with proper size NPT thread instead of the tee with 2 plugs?

rv_safetyman · February 20, 2011, 02:32:57 PM

Rich, Jack Conrad wrote an excellent article for BCM on the conversion process to rolling diaphragm air bags. As I recall, it was not all that complicated.

Jim

Oonrahnjay · February 21, 2011, 05:50:00 AM

Quote from: brando4905 on February 20, 2011, 12:51:57 PMBruce,

Is there any reason why you couldn't just use a brass cap with proper size NPT thread instead of the tee with 2 plugs?

No reason at all -- they just seem to be devilishly hard to find near me; the T's and plugs are available at most all hardware stores. And there's the added benefit with a T that you can re-attach your through line, add a Schrader valve, and check air pressures with your tire gauge. But if you have or can find a plain cap, they're good for diagnostics, too. In fact, a plain cap offers fewer points for possible leaks while you're doing other tests. But the T with plugs works well, is very flexible (allows a pressure test port, as noted above, allows you to branch off and bypass a problem area, allows multiple lines to be blocked off, etc.), and is easily available.

bevans6 · February 21, 2011, 10:18:18 AM

And here I thought the reason for the Tee was that you can spin it on and off and get it tight enough to seal for a quick test with your fingers, no wrench. Speeds things up a tad!

Brian

Oonrahnjay · February 21, 2011, 08:24:53 PM

Quote from: bevans6 on February 21, 2011, 10:18:18 AMAnd here I thought the reason for the Tee was that you can spin it on and off and get it tight enough to seal for a quick test with your fingers, no wrench. Speeds things up a tad!
Brian

Another good factor!