Air Beam Leak

Stormcloud · January 25, 2015, 04:30:18 PM

I finally tracked down the cause of my MCI7 front suspension settling down onto the stops in near-record time.

A pinhole leak in a weld in the air beam, just forward of the drivers front wheel. The weld is a horizontal bead along the top of one 'frame' section where it is welded to another. The undercoating has failed in quite a few spots on the welds and steel there. I hope a competent welder ( not me! ) can run a new bead on top and fix this up. Of all the places that it COULD leak, this is likely the best! It's fairly easy to access.....the wheel doesn't need to come off to reach it!

I think I should buy a lottery ticket!

Mark

chessie4905 · January 25, 2015, 04:33:40 PM

All is good if that is the only leak. Or you could go with the block off plates to bypass the air beams function.

Stormcloud · January 25, 2015, 04:39:08 PM

Yes, I considered the block-off plates and will definitely resort to them if I have to.

I'm fairly sure this is going to be an easy fix; however, I have been wrong before.

mung · January 25, 2015, 04:41:08 PM

If it is only a pin hole, JB weld or something like that?

Stormcloud · January 25, 2015, 05:25:17 PM

JB may indeed hold, but I think I'm gonna try the real thing.

Because the leak is at the top of the steel beam, there's no way to get any tire 'slime' to it. In the past, I had to use some of that slime on one of the rear bags that just would not seal against the plate. Still sealing just fine after several years.

Mark

gumpy · January 25, 2015, 07:36:27 PM

Likely, when your welder starts to work on that hole, he will make several new ones. That steel may well be so corroded that it is very thin by now
and trying to weld up a leak like that may only create more problems. I went through exactly that on mine when I had it all apart. The more I welded,
the more holes I had. I did finally get it to seal up, and it has been holding, but...

Welds don't normally just develop pin holes after 40 years. There's a reason that hole appeared.

Good luck. It's worth a try, but don't be surprised if it can't be patched.

B_K · January 25, 2015, 08:42:04 PM

If it welding it doesn't correct it consider going with the "rolling lobe" air bags and not just "block off plates and stock bags.
The rolling lobe bags will give a much smoother ride.

BK

wg4t50 · January 25, 2015, 08:46:42 PM

IF this air leak is a new issue, be careful when you start welding, that air beam might be rusted more than you suspect and you get into a mess, having had a MC7, I never needed the block off plates for the front, but sure would give em a good thought.
Dave M

Rick 74 MC-8 · January 26, 2015, 02:13:24 PM

I replaced the front bags with rolling lobes and block off plates on my MC-8 last year. seems to actually ride better. Feels like less unsprung weight not that there is but it feels that way. I got the kits from Mohawk. Great people. Very easy to install hardest part was getting the old bags off.
I did plate the beams I didn't have to worry about leaks

Rick

Lin · January 26, 2015, 03:49:04 PM

If a weld would work, that would be the easiest way to go. It is true that the one small leak could be a sign of deeper corrosion issues, but you might as well find that out now. I am sure a good welder will be able to tell you by merely doing his prep work. If it is worse than it looks, then it may need to be reinforced even if you will also need to plate the air beam. Rust will not merely go away by ignoring it.

B_K · January 26, 2015, 07:09:49 PM

Quote from: Lin
Rust will not merely go away by ignoring it.

Does too! If you don't believe me ask Bobby Easter how many rusty units he ignored that went away!

BK

Lin · January 26, 2015, 07:35:49 PM

Would he actually admit even one?

B_K · January 27, 2015, 10:22:07 PM

Quote from: Lin on January 26, 2015, 07:35:49 PM
Would he actually admit even one?

Probably not but we know enough witnesses to prove it!

BK

Stormcloud · February 19, 2015, 07:56:55 AM

I took time this morning to have a closer inspection, and I'm not real happy.

The air beam appears to be leaking along the top edge where some other metal,etc is in close contact. I can' tget a real good look at it until I block up the front end and pull the wheel and inside fender, but I think to do a proper repair, the floor is gonna have to come out, just aft of the drivers seat....

Or...

blockoff plates on all 4 front bags...

Is it too early for Bailey's in my morning coffee?

bevans6 · February 19, 2015, 09:21:08 AM

That is the classic failure, I am told. I would do block off plates after making sure the structure can still safely transfer the load from the chassis to the axles. Most people seem to be very happy with that repair.

Brian