found my air leak, but a lttle confused

Seann · October 27, 2025, 11:26:16 AM

Hi Folks,
Finally got pass rear drive wheels off (MC9) to look for big leak/valve problem that would not let the pass side air up. Used shop air line to chase leak down and felt large leak at the middle fitting going into the rear facing bulkhead up above air tank (see photo)...leak was where the threads met the wall. I pulled the leveling valve and the suspect line from the regulator, thinking the bulkhead fitting must have failed somehow. When I got the line out, it appears the fitting has just "come out". Is that an air beam that it was threaded into? The line fitting is still tight, and the adapter threads look fine. Anyone explain what's happened here?
Thanks,
Seann

Seann · October 27, 2025, 11:28:39 AM

more photos

Seann · October 27, 2025, 11:29:12 AM

2 more

lovetofix · October 27, 2025, 04:46:54 PM

Your steel bulkhead fittings have rusted away from the brass flare fittings.
You will need to take the cover off the bottom of the tunnel in your rear bay and replace those bulkhead fittings.
Here is what your fittings used to look like.

lovetofix · October 27, 2025, 04:56:00 PM

Here is the other side of that bulkhead.
You can drill out that old fitting and use a coupling between the two brass flare fittings.
And a clearer picture of the wheel side.

Seann · October 28, 2025, 07:33:54 AM

Thanks for the photos and explanation...have to remove large water tank today to get at the access panel, picked up a coupler (although it's quite short), maybe have a solution today.

Seann · November 09, 2025, 06:06:23 AM

Thanks lovetofix...you were right, the bulkhead fittings literally crumbled away from the air lines. I had to do 2 of them, made up new lines/fittings, sits level at the back now. Next issue is the front, sits low on pass side, bags are airing up, wondering if it's a seized shock or plugged inline filter...
Seann

belfert · November 09, 2025, 03:00:19 PM

Does it make sense to just replace sections of copper with plastic DOT line when these things happen? My two Dina buses are new enough to have all DOT plastic air lines. No broken plastic air lines that I can recall.

The 1995 will maintain air for weeks in warmer weather, but will leak out the air when it starts getting under 32F. (System is dry so far as I know. No water comes out of air tank drains.) Now, I had to spend a fair bit of time to get the air system leak free when I first got the 1995. My 1999 I just got, and it definitely leaks air from the air operated door and air step. I am going to remove the air door completely so that stuff will get capped. I just haven't had time in the three or four weeks I have had the 1999 to fix any of the air leaks yet.