Air suspension acting up

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bertro

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Well, it had to happen one day. Don't have $$ for the conversion right now so i'm hoping to figure out what's wrong and fix it. Hope one of you can help with ideas.

So I've noticed that the rear deflates completely and sags a few minutes after I turn the engine off. It sags on both sides, little more on the driver side. But when I turn the engine on, the bags inflate to the normal ride hight and all is well.
At first I thought I might have a leak somewhere (bags, valves), but I disabled the air ride while the truck was running and the bags were inflated, then turned the engine off and the bags remained inflated (it's been over 24 hours since I did this and the bags are still full), so I don't think there's a leak.

Could it be that the rear hight sensor went nuts and thinks the truck sits too high and so tells the valves to deflate the bags all the way when I turn the engine off?

Any ideas?

thanks!
 
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bertro

bertro

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Ok, so I'm beginning to suspect the rear height sensor is the issue. I've just noticed that now when I start the truck the rear lifts visibly higher than it used to. Almost as if I were in 4x4Lo (which i'm not in). And when I stop the engine, it doesn't kneel down as low as it should.
So I guess the sensor sometimes reports too much height (which made the bags deflate all the way last week) and sometimes reports too little height, which makes the bags overinflate and the truck ride higher than normal. I won't replace it just yet and will keep an eye on it. I'm just glad the issue was not a leak.
 

reefkrazy

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20130309_154405_zps568db082.jpg

Check this sensor. I have raised mine to go higher but yours should be sitting on that ball looking thing. Maybe it shifted on you.
 
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bertro

bertro

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Thanks! Are there sensors near both rear wheels or just on one side?

Btw the truck has been sitting since Thursday evening and now the rear is all the way down again. Guess i'll test the fittings with soapy water too just in case.
 

reefkrazy

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It's only one on the driver side. Its to left of the deferential by the fill hose. The front is (just one) on driver side as well just in case you wanted to know.

20130309_154448_zps9f1f8927.jpg

Also is the switch in the off position? Passenger side under dash near door ?
 
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bertro

bertro

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It's only one on the driver side. Its to left of the deferential by the fill hose. The front is (just one) on driver side as well just in case you wanted to know.

20130309_154448_zps9f1f8927.jpg

Also is the switch in the off position? Passenger side under dash near door ?

Thanks for the info and pics. Just realized you have a 1st gen. Mine is a 2004, hope the sensors are in the same place. I'll try crawling under the truck this weekend if the weather is decent.

Yeah, the air ride switch is on. I've turned it off one day last week after starting the truck just to lock the valves shut and see if the bags lose air once I turn the engine off and let it sit for a while. They didn't lose any air, so i came to the conclusion that the bags and valves don't leak. I turned the air ride back on after that test.
 
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bertro

bertro

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Ok, so this is getting f'in weird. I removed the rear left wheel over the weekend and noticed that the bag on that wheel had no pressure at all. I could squeeze it with my hand and would hear the air hiss towards the plastic top of the bag. The other bags were pressurized and impossible to squeeze.

I put soapy water on the air line connection and all around the air bag but could not see any obvious leak. But anyway I was ready to order a new bag (they're about $100) and replace the dead one.

But then yesterday I went shopping for some concrete pavers for my patio. Filled the back of the Expy with about ~1000lb of concrete pavers and the rear suspension didn't sag at all when I turned the truck off. I've left the pavers in the truck over night and the suspension is still not sagging. The rear left bag is nice and inflated.

I don't friggin' understand what's going on. If there's a leak, I imagine it would have deflated even faster with 1000 pounds of added weight. I inspected the hight sensors and they seem to be in their proper place. And they seem to be working: the truck lifts when I start the engine, and then "kneels" when I stop. It's just that darn rear left bag that acts up...

BTW: to change the bag, do I need to remove the entire strut, including the metal part?
 
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reefkrazy

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When you removed the wheel ( on jacks or suspended for a period of time) did you turn the switch off? If not, the bag will totally deflate and take quite some time to fill back up again. This is normal. I got tires replaced by a shop and they didn't turn the air ride switch off. When the truck came down with 33's it was slammed. looked like a lowrider. took about thirty min to inflate.
 

1997SCEBFEX

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Not sure if related or not, but on my 1st gen, there is an air union coupler under the master cylinder that will fail over time. initial indications may be what your are experiencing. if it does fail, the rear will completely sag. as I was trying to figure out what had happened, i traced the air line, found the break, re-energized the system and held the line together long enough to get air into the rear, then turned it off until I could get the replacement part. Sometimes the o-rings will start to deteriorate ever so slowly and that may also be what you are experiencing?

as far as removing strut to replace bag, can not answer, but did not have to remove anything on mine except for the tires to replace both bags.

PanHandler.
 
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bertro

bertro

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When you removed the wheel ( on jacks or suspended for a period of time) did you turn the switch off? If not, the bag will totally deflate and take quite some time to fill back up again. This is normal. I got tires replaced by a shop and they didn't turn the air ride switch off. When the truck came down with 33's it was slammed. looked like a lowrider. took about thirty min to inflate.

Yup, turned the switch off before lifting the truck. The bag was flat as hell and I could squeeze it and hear air hissing at the top of the bag.

Anyway looks like i'll need to replace that whole bag&shock assembly because the shock just dumped all of its oil on my driveway today. F&$k!
 
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