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Topic: Replaced rear air bags, now rear end drops overnight (Read 650 times) previous topic - next topic

Replaced rear air bags, now rear end drops overnight

So we replaced the 4 rear air bags and all seemed good on the drive back to storage.  However, upon checking the coach a day later I found the rear end had completely dropped.  Front is normal.  Started coach and it will raise to travel height.  Shut off the engine and checked it again the following day and again, the back end was completely deflated - both wheels touching the top of the wells - and front was still up.

I'll take it back over to the shop tomorrow and have it checked.  I'm very pleased so far with their work and they will probably figure it out.  I'm guessing one of the connections is leaking air; But, I wanted to ask you all for any ideas you may have.  Never had any leakdown issues before so I think ride height valves were all ok. Seems strange to me that both sides leaked down equally; I thought if a valve was leaking then one side would drop more than the other..

Any thoughts or experiences you all could offer would be appreciated.
1996 U295 36' WTBI

Re: Replaced rear air bags, now rear end drops overnight

Reply #1 –
Some of the elbows need to be oriented correctly for air line routing and sometimes the elbow fitting ends up being tight in the wrong position and a mechanic might remove the fitting redope it and reinstall only not going so far with the tightening. (If they are overcranked the brass fittings may break inside the airbag fitting and cause more problems.) This may leave the fitting prone to leakage. Do not use teflon tape on the fittings. Should use an anaerobic pipe sealant (one of the best is loctite 565)
- Henkel North America
if reusing old elbows (must clean them well) or replace elbows with new ones that have the sealant applied at an approved applicator. New elbows can be had a truck supply shops and the elbows will have a red band of sealant already applied although no gaurantee as to what they used but a high quality shop knows the suppliers and should get the good stuff to you.
Good luck,
Rick
Rick

Re: Replaced rear air bags, now rear end drops overnight

Reply #2 –
You guys told our story, which is EXACTLY the same as our situation. Had 8 air bags changed a week ago, everything was fine for 4 days and after a drive home, we find our rear and left side are low. Must be something contagious going on.

We found by soap leak detector spray, our left rear tire's rear air bag 90 degree fitting leaking at the pipe thread going into the air bag. Since each tire's two air bags are plumbed together, the fitting leak caused two air bags to lose air. Our coach has compression air hose fittings, and not push on fittings. And we can reach the air fitting from the little door behind the tire.

To keep us level so we could keep our satellite antenna properly aimed, I put one of our four steel safety bars next to the left rear tire's forward air bag, then leveled with the right side. Level held fine, but the next day, our bay doors would not open because we had torqued our frame. We then aired up coach with engine compressor, and put another safety bar next to the left rear tire's rear air bag, so both leaky air bags were supported and re-leveled. Coach frame and bay doors were ok by using two safety bars.

Truck air lines use a 'special' compression size, that is a little larger than hardware store compression fittings. So I went to a truck parts store and bought two right angle compression brass fittings with pipe thread on one end. When new air bags were put on, the original compression fittings were re-used. I replaced the fitting that was leaking at the pipe thread, adding lots of Permatex sealant that we just talked about in another Forum thread, to the factory sealant that was already on the new fitting. Then reused the original compression hose fitting, because replacing the hose compression would require cutting the hose back about an inch.

Well, the next day, the back end was down again. My sealant on the pipe thread was not leaking again. This time it was the compression end. So I installed my spare right angle fitting, with more Permatex sealant. Only this time, I was able to get an little more length out of our air line by removing some of the original cable ties and re-routing the air line. Then with a PVC cutter, I sliced off the original compression fitting from the air line and used the new fitting's compression ring & nut.

It has been 8 hours since the last repair and we are still level. We also never had any leak down before changing air bags, so we were also dismayed that by changing air bags that were working fine, we caused an air leak. But we are happy that we have new air bags and besides the other 7 original air line fittings did not leak.

Good luck Chris & Amanda.

Re: Replaced rear air bags, now rear end drops overnight

Reply #3 –
Thanks so much. First question will be about the fittings being reused or not.  I think they were, so we'll most likely be changing those tomorrow.

BTW, my shop is so impressed with the Foretravel info available here and on Beamalarm. You all are the best.

Chris
1996 U295 36' WTBI

Re: Replaced rear air bags, now rear end drops overnight

Reply #4 –
Just an update: we replaced all the brass elbows (they had re-used the old ones) on the new air bags and all is well now. Thanks again for the great advice.
1996 U295 36' WTBI

Re: Replaced rear air bags, now rear end drops overnight

Reply #5 –
Excellent. 
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Replaced rear air bags, now rear end drops overnight

Reply #6 –
Did they re-use the air line compression fitting or did they cut the air line and put on a new compression fitting?

Re: Replaced rear air bags, now rear end drops overnight

Reply #7 –
New fittings...described to me as the "quick connect" type.
1996 U295 36' WTBI