XUV air supension question

emedlin

Original poster
Member
Jan 25, 2012
150
Looks like I need to find a leak, as over the weekend my 04 XUV was all the way down on both sides come Sunday morning after parking it Friday night. Same thing happened last weekend also. During the week it only drops 1/4" each night though, so once it gets past a certain point it must leak out faster. Does that make sense? Now my question is, are the left and right air bags connected in a way that if one has a leak both sides will go down? Judging by recent posts it doesn't sound hard to change the air bags out, and the parts are around $200. Are the air bags the normal place to look for leaks? What about the air lines going to them? Can the compressor get a leak?
 

RayVoy

Member
Nov 20, 2011
939
Air the bags up and use a soapy solution to paint everything (bags and lines). The air passing through the soap will cause bubbles.
 

jeffro312

Member
Oct 4, 2012
442
East Haven,Ct
Curious as to what is normal rate bags deflate. I'm sure there not going to stay inflated for ever... I leave my Rainier parked on an incline and tailpips barely touching ground In 3-4 days of no use. I assumed was normal as during regular driving pump does not run that often
 

BRomanJr

Member
Dec 9, 2011
371
emedlin said:
Looks like I need to find a leak, as over the weekend my 04 XUV was all the way down on both sides come Sunday morning after parking it Friday night. Same thing happened last weekend also. During the week it only drops 1/4" each night though, so once it gets past a certain point it must leak out faster. Does that make sense? Now my question is, are the left and right air bags connected in a way that if one has a leak both sides will go down? Judging by recent posts it doesn't sound hard to change the air bags out, and the parts are around $200. Are the air bags the normal place to look for leaks? What about the air lines going to them? Can the compressor get a leak?

Yes, the Compressor can leak, there is an integral check valve problem that was documented in a TSB. The compressor also contains other solenoids.
The left and right side share one compressor and intake check valve, but each side is separate form there. Each side has a fill solenoid (in comp), vent solenoid (in comp), height sensor (near each wheel), line and bag.

The bags most often are the culprit, The check valve could be second on the list of failures. The lines are least suspect.
The compressor is usually only changed when it fails to run or runs but fails to lift and no leaks are found.

There is also the lighted switch at the interior rear fill valve, with some Electrical problems it will blink a code.

My personal experience:
My XUV occasionally lowers slightly over a period of time, but is doing great lately.
 

emedlin

Original poster
Member
Jan 25, 2012
150
BRomanJr said:
Yes, the Compressor can leak, there is an integral check valve problem that was documented in a TSB. The compressor also contains other solenoids.
The left and right side share one compressor and intake check valve, but each side is separate form there. Each side has a fill solenoid (in comp), vent solenoid (in comp), height sensor (near each wheel), line and bag.

The bags most often are the culprit, The check valve could be second on the list of failures. The lines are least suspect.
The compressor is usually only changed when it fails to run or runs but fails to lift and no leaks are found.

There is also the lighted switch at the interior rear fill valve, with some Electrical problems it will blink a code.

My personal experience:
My XUV occasionally lowers slightly over a period of time, but is doing great lately.

Well I have it up on a set of ramps and I have sprayed down the bags or atleast the bottom halves up them, but I don't see any leaks yet. Based on what you said is it correct to assume if both sides go down then it is not the bags or lines, but the integral check value or the compressor as those are the only common parts that would cause both sides to go down? What does the integral check value do? I am running under the assumption both bags didn't get a leak at the same time.
 

northcreek

Member
Jan 15, 2012
3,320
WNY
emedlin said:
Well I have it up on a set of ramps and I have sprayed down the bags or atleast the bottom halves up them, but I don't see any leaks yet. Based on what you said is it correct to assume if both sides go down then it is not the bags or lines, but the integral check value or the compressor as those are the only common parts that would cause both sides to go down? What does the integral check value do? I am running under the assumption both bags didn't get a leak at the same time.

My limited exposure to this system seems to show me that the compressors are usually the culprit,not so much the compressor portion but,the electronics and valving incorporated within.Being an 04 you have probably reached the life span of the unit.I bought a spare to have on hand in anticipation of mine crapping the bed.It seems that these units have shorter lives in the saltier,damper northern climates...Mike.
 

emedlin

Original poster
Member
Jan 25, 2012
150
Well I sprayed them down 3-4 times and never did find a leak, so I guess I will just wait to it gets worse. Might look into the integral check valve on the compressor. I could use some info on that if you have any.
 

emedlin

Original poster
Member
Jan 25, 2012
150
I found part #15183676. It is the ECAS Compressor Service Kit. But the TBS says it is for the 02 not my 04. Are they the same? Also the problem in the TBS is the rear is low and the compressor will not raise it. My compressor raises it back up fine.

So, my envoy leaks all the way down if it sits for a few days without moving. After one night or even a full 24hours I only measure maybe 1/8 - 1/4" drop. It drops on both sides so the bags and hoses are fine. The compressor raises the vehicle back up, so it's not the check value that I can replace with the service kit. Do I need a new compressor?
 

northcreek

Member
Jan 15, 2012
3,320
WNY
emedlin said:
I found part #15183676. It is the ECAS Compressor Service Kit. But the TBS says it is for the 02 not my 04. Are they the same? Also the problem in the TBS is the rear is low and the compressor will not raise it. My compressor raises it back up fine.

So, my envoy leaks all the way down if it sits for a few days without moving. After one night or even a full 24hours I only measure maybe 1/8 - 1/4" drop. It drops on both sides so the bags and hoses are fine. The compressor raises the vehicle back up, so it's not the check value that I can replace with the service kit. Do I need a new compressor?

The check valve is the only seviceable part of the compressor.You could remove it and see if it is damaged or might just have some debris that needs to be cleaned out.If everything looks ok you will probably need a compressor unit.Look through some of the past posts,the proceedure has been covered before...Mike.
Look at the pictures here,the plate with the two screws is the valve> https://www.arnottindustries.com/part_GMC_yid15_pid138_gid537.html
 

emedlin

Original poster
Member
Jan 25, 2012
150
Had it leak all the way down overnight a few days ago. But was fine over the weekend. It really does seem like a valve not sealing up good sometimes. It seems way to random to be hole in a bag or line.
 

BRomanJr

Member
Dec 9, 2011
371
emedlin said:
Had it leak all the way down overnight a few days ago. But was fine over the weekend. It really does seem like a valve not sealing up good sometimes. It seems way to random to be hole in a bag or line.

Your intermittent leak is probably inside the compressor. You are reading the TSB correctly, a bad Check Valve (compressor intake) will prevent a running compressor from lifting up.

IMHO the problem is with the internal solenoid valve sealing surfaces, I had a similar problem and carrying a few loads of lumber has made it trouble free for a while now.
Not sure if the unit can be disassembled for cleaning or not. My truck spent most of its life in Florida before I bought it so it doesn't yet have the corrosion issues from Michigan winters.
 

emedlin

Original poster
Member
Jan 25, 2012
150
Well I still haven't swapped the compressor out. But, I now know about how long it takes to leak out. My wife went into the garage and heard this loud hissing sound. The Envoy looked fine, so she though I had left something running. She went back inside and then less than 5 minutes later went back to the garage. The sound had stopped and the Envoy was on the ground. So my Envoy can sit days without a problem or leak completely out in a few minutes. Has anyone else seen one leak out that fast? I still assume it is the compressor, but I never imagined it leaking out that quickly. What in the compressor or anywhere else would cause it to be fine then just all of the sudden leak out that fast?
 

The_Roadie

Lifetime VIP Donor
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Nov 19, 2011
9,957
Portland, OR
emedlin said:
What in the compressor or anywhere else would cause it to be fine then just all of the sudden leak out that fast?
The compressor has valves to allow compressed air IN to pump them up (and keep them inflated) and other valves to vent the bags OUT in case you remove cargo from the rear and they're too high. Either one of these sets of valves (I think there's one for each side) can have a faulty/dirty sealing surface that allows leakage. That can be an intermittent or erratic problem.
 

jeffro312

Member
Oct 4, 2012
442
East Haven,Ct
the roadie said:
The compressor has valves to allow compressed air IN to pump them up (and keep them inflated) and other valves to vent the bags OUT in case you remove cargo from the rear and they're too high. Either one of these sets of valves (I think there's one for each side) can have a faulty/dirty sealing surface that allows leakage. That can be an intermittent or erratic problem.

Roadie are these valves/valve seals serviceable or better to just replace compressor
 

emedlin

Original poster
Member
Jan 25, 2012
150
Well I had it deflate while driving recently, so I really need to take care of this. I noticed it was down when I turned in the driveway and the rear mudflaps dragged the ground. I guess the compressor couldn't keep up with the leak or just didn't turn on. I have observed it deflate within about a minute while sitting the garage a few times now. I hear the air start coming out and down both sides go. Sometimes all the way and sometimes just half way down. I thought I heard most of the air coming from the driver side, but isn't the compressor on the passenger side? Also one of the last times it went down when I started the car the compressor didn't turn on. I went and flipped the switch to turn on the compressor in the bed and it turned on, but when I turned it off the compressor turned off. I expect it to stay on since it was sitting on the ground. I few flips between on and off and it eventually stayed on and raised the car without issues. Why, bad sensor? So now I am not sure what the problem or problems are. If the compressor is leaking why did I hear the air on the drivers side, need to check this more? But if both sides always deflate together at the same amount and do so at a random time at a rapid pass how can it be the air bags? I though that would be more of a slow or at least constant leak and not both sides at the same time.

My wife likes the air ride system, actually she just likes things stock and working, so I would rather have that system working. However, I did find Suncore 148G-30-R Regular Rear Suspension Air Bag to Coil Spring Conversion Kit for under a $100. That sounds like a easy cheap full proof fix. My shocks are only a year old, I don't need to get new ones if I switch to springs do I?
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,053
Brighton, CO
You will have to replace the shocks as well. You could also find the springs, and spring seats, at a local junkyard, and it might even be cheaper. Than it would be just a matter of heading to your favorite auto parts store, and getting new shocks.
 

emedlin

Original poster
Member
Jan 25, 2012
150
TollKeeper said:
You will have to replace the shocks as well. You could also find the springs, and spring seats, at a local junkyard, and it might even be cheaper. Than it would be just a matter of heading to your favorite auto parts store, and getting new shocks.

What are different about the shocks?
 

jrSS

Member
Dec 4, 2011
3,950
emedlin said:
What are different about the shocks?

If your about the same ride height with springs (converted from bags) you will be fine. No need to replace shocks.
 

The_Roadie

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Nov 19, 2011
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Portland, OR
I've never discovered the precise difference in the shocks in 8 years. I suspect it's a tiny change in valving. Many members over the years have converted to coils and not changed shocks and didn't report any noticeable difference.
 

BRomanJr

Member
Dec 9, 2011
371
emedlin said:
What are different about the shocks?

From what I've read, the air bag suspension uses slightly shorter shocks to keep the air bags retained as the bags do not extend as far as springs when free.
 

emedlin

Original poster
Member
Jan 25, 2012
150
the roadie said:
I've never discovered the precise difference in the shocks in 8 years. I suspect it's a tiny change in valving. Many members over the years have converted to coils and not changed shocks and didn't report any noticeable difference.

Good to know. If I switch to springs do I need HD ones or are the Suncore 148G-30-R ones fine? Or are there other good <$100 ones? I don't tow or haul anything. Most it has is a stroller and groceries in the back. My only concern is it is an XUV, so it's heavier than your average Envoy. Would still like to prove one way or the other if it is the compressor or the bags though. I could see replacing one or the other if I knew for a fact which one to replace. But $350 for a compressor and then maybe $200 for bags if that doesn't fix it is just a lot of cash when springs are <$100. So, I am starting to lean towards springs to replace the bags and keeping the compressor just for the random pool float, tire, etc. instead of removing it also.
 

The_Roadie

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Member
Nov 19, 2011
9,957
Portland, OR
In the factory, the GM build computer chose from an array of 10-12 different coil spring stiffnesses, according to the vehicle type and option list. So an EXT/XL vehicle would weigh the most, especially if it had 4WD, and get the stiffest coils. Many offroaders put in one of the three stiffest springs in the front, even for short wheelbase vehicles, to get extra ground clearance.

Here's the ORTB chart for front spring choices:

tb-springs.jpg


I don't have a similar chart for the rear because we never use GM Trailblazer/Envoy springs for rear lift. But you have a LOT of choices out there for under $100. Moog makes front replacement coils in three stiffnesses, and I expect they also have choices for the rear. Arnott offers some. Since the 2007+ Tahoe/Avalanche uses the same rear spring perch, most offroaders are using springs that fit that platform, such as Skyjacker lift springs or GM Z71 option OEM progressive coils that give about 1.5" more ground clearance. And if you value adjustability for cargo or variable hitch weight for towing, throw Airlift1000 bags inside the coils and inflate them manually as helpers.
 

BRomanJr

Member
Dec 9, 2011
371
emedlin said:
Good to know. If I switch to springs do I need HD ones or are the Suncore 148G-30-R ones fine? Or are there other good <$100 ones? I don't tow or haul anything. Most it has is a stroller and groceries in the back. My only concern is it is an XUV, so it's heavier than your average Envoy. Would still like to prove one way or the other if it is the compressor or the bags though. I could see replacing one or the other if I knew for a fact which one to replace. But $350 for a compressor and then maybe $200 for bags if that doesn't fix it is just a lot of cash when springs are <$100. So, I am starting to lean towards springs to replace the bags and keeping the compressor just for the random pool float, tire, etc. instead of removing it also.

I wouldn't fret about the XUV possibly being heavier, the rear roof is plastic and it does not have the third seat or the Rear HVAC.
The midgate adds a few pounds and the endgate may be a few pounds more than a liftgate.
They may be close enough to call it a wash.
 

emedlin

Original poster
Member
Jan 25, 2012
150
I found Moog 81049 for $50 and Arnott C-2137 for $250. Are Anrott's really that much better. What makes it a conversion kit or is that just Anrott marketing to charge more? Also neither of these say they come with coil insulators like the Suncore's do. I assume these are needed to avoid squeaking. Don't want to raise it or need to tow anything, so the Z71 springs are not needed.
 

emedlin

Original poster
Member
Jan 25, 2012
150
the roadie said:
Yep. Spec sheets say SWB = 4417, XL = 4968, XUV = 4917 (varies a small amount per year)

What do those numbers mean or what is it a measurement of? Would be nice to compare it to other springs before I order them.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
emedlin said:
What do those numbers mean or what is it a measurement of?
Curb weight. Spring rates were/are a closely guarded secret that required a GM insider to share the dirt for us to assemble. Aftermarket spring vendors like Moog are also cagy, and sometimes require a call to factory tech support engineering to find out. And they seldom have any enthusiasm for applying a spring in a non-recommended application, due to liability-lawyer-fears.
 

kkoether

Member
Aug 18, 2013
37
Our 2004 Rainier started dropping in the rear overnight. I'm not sure if the airbags were the originals or not. We bought it in 2010. I ended up just going ahead and replacing both bags. If I remember I got a pretty good deal directly from Arnott Industries on their replacement bags. Neither of the old bags had holes in them. They were leaking from the seal for the lower side of the airbag where they rubber mates with the lower plastic cup that sits on the axle. It's been several years since I replaced them and they are still working fine.

https://www.arnottindustries.com/part_BUICK_yid10_pid121_gid494.html

Should most likely be the same for the XUV.
 

jrSS

Member
Dec 4, 2011
3,950
If u want some stock oem bags....I have a set with low mileage and no cracking.
 

emedlin

Original poster
Member
Jan 25, 2012
150
Going to order a set of MOOG 81049 springs and a two MOOG K160072 spring insulators to go on top of the springs and fix it for good. At 125K miles no matter which is bad now the other is not far behind it. I just don't thing the air system is worth the cost since I don't tow anything. If anyone knows those are not good or the correct parts please let me know.
 

darsch

Member
Mar 28, 2014
33
I've got a somewhat similar problem with my Bravada and hopefully someone can point me in the right direction.
The rear, when unloaded seems to be basically at the proper level, maybe a bit low but never drops down beyond a certain acceptable height overnight or over the week. Ever since I overloaded a trailer one time, the pump has never been able to fully compensate for other light loads that I may carry and the pump seems to run louder now. It doesn't pump enough air now to fill a tire using the fill switch and connector in the back panel. It did fine before the heavy load. The air bags are cracked, I haven't put soapy water on to see if they leak but the suspension is always level side to side so I think they aren't leaking plus they never go lower than a certain point or seemingly certain air pressure.
Now from lots of reading lends me to ask would installing the valve repair kit in the compressor fix the problem and get me back to full pressure or would it be something else inside the pump? Does the warn valve cause a louder pump? I hate throwing parts at things and if it doesn't work and something drastic happens that it won't fill the bags up at all afterwards, then I'm stuck with a broken truck and would have to order other parts in.
I know I have to replace the bags because of the cracks but my other option is to replace everything with springs like some of you have done but I like the air ride.
I used my trailer yesterday and with it empty and the compressor wouldn't bring the ride back up at all and so the truck squatted pretty low.
I'm thinking of loosening the pump off this afternoon, cleaning it up and looking at it to see if there is something obvious, if it doesn't start raining.
Thanks.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
Welcome! A lot depends on how deep your pockets are, and do you value the automatic air suspension enough to throw $500-600 at it with a total Arnott replacement system.

Otherwise go for the coil springs, throw Airlift1000 bags inside them if you want to compensate for hitch weight, and be done with the complexity forever. Sleep better at night, too I predict. And your dog will be better behaved. And your complexion will improve. And your clothes will become self-ironing. :biggrin:
 

darsch

Member
Mar 28, 2014
33
My budget it really small.
After reading some more forums on this similar problem I'm starting to think now that maybe it's a sensor. My pump goes on for 20 seconds or so after vehicle startup like it's supposed to whether the level is correct or not but it doesn't go on again if the ride level is low. Shouldn't the pump keep going and try to lift the truck if the ride height sensor is working properly? Is there a way to test this sensor? I think someone said there is a movable arm or something somewhere?
Still doesn't solve why it won't inflate a tire though. Doesn't seem like these two things should affect each other.
 

northcreek

Member
Jan 15, 2012
3,320
WNY
darsch said:
My budget it really small.
After reading some more forums on this similar problem I'm starting to think now that maybe it's a sensor. My pump goes on for 20 seconds or so after vehicle startup like it's supposed to whether the level is correct or not but it doesn't go on again if the ride level is low. Shouldn't the pump keep going and try to lift the truck if the ride height sensor is working properly? Is there a way to test this sensor? I think someone said there is a movable arm or something somewhere?
Still doesn't solve why it won't inflate a tire though. Doesn't seem like these two things should affect each other.
If you have an inflation station at the rear like I do, check the led light for a code, it blinks a 1,2 or 3. If you don't have much $$ you should do the spring conversion because after you replace the bags and that does not fix it you will need a compressor assembly. Don't bother with the check valve replacement, usually the internal parts fail and they cannot be replaced...Mike.
 

darsch

Member
Mar 28, 2014
33
It's never given me a code there, only when it overheats from trying to fill a tire will it flash, turn off and then resume once it cools.
I called a mechanic and he says that if it senses an air leak in the system, the pump will not turn back on to save from wearing out. So the problem shouldn't be the ride height sensor.
I can get the Moog springs and insulators for about $140 + tax and do what emedlin did. Are new shocks really needed? If I didn't like the air ride so much it would be an easy decision to switch over to coils so I need to explore all options first. Anyone else happy or unhappy with the Moog springs?
 

darsch

Member
Mar 28, 2014
33
So my cheapest options are as follows:
1. Replace the air bags with new coil springs for $140.
2. Replace the air bags with used coil springs for $100.
3. Replace the weather cracked and probably leaky air bags with new aftermarket ones for $180, buy a T fitting, run the air lines into the T and adjust the bags manually with an air compressor from in the truck. I would then be bypassing the onboard compressor.

I really like the ride of the air suspension so I am leaning towards #3.
 

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