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2002 gmc envoy_slt
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Hi, my name is Jeremy and this is my first post. Anyway, my wife has an '02 Envoy 4wd with the air suspension in the back. Well, after sounding worse and worse, the pump finally gave out. I checked the dealer and they wanted $474.00 for a new one! Cheapest I could find it online was $370ish, which was still way more than I am willing to pay. I didn't want to get a used one, since it will probably not last too long either, giving my luck. So I figured I would take the old one off to see what I was working with. Pretty easy, just 2 13mm bolts, 2 wiring connectors, 3 (1 for each air bag and 1 for the accessory outlet in the cargo area)5/32" plastic hoses which are threaded, and 1 rubber hose for the intake of the pump which goes into the cargo area.
I pulled the ferrules off the plastic hoses, then the pieces that thread into the pump. So now I had three bare, 5/32" hoses hanging where the pump used to be. Two of them for the bags, and one still connected to a schraeder(sp?) valve in the cargo area(the one for inflating things for 2 minutes before it overheats and shuts off):rolleyes:. So I went down to a local rubber/hose supply store and bought a 5/32" union tee with push in connections. Came home, pulled the fuse for the eacs under the hood, plugged the three hoses into the tee, and taped up the electrical connectors and intake tube to keep dirt/moisture out. Then I plugged my portable air compressor into the valve in the cargo area and pumped it up to normal ride height, which was around 50psi. It works great and it only cost $5.30! Plus, I can adjust the ride height any way I want to(within reason)!
Pics to come later tonight. Sorry for the book.
 

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2002 chevy trailblazer_lt
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69 Posts
Does it hold 50 psi fairly well? I figured it would make the drive a little stiffer if it were at a constant level at all times. Good luck with it though. 5 bucks sounds a whole lot better that almost 500. Good job.
 

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2004 gmc
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Not a problem at all. Very clever workaround, and it's like what we do when we add Airlift1000 bags inside coil springs to get more lift or less sag under load. At this point, you could spend $125 (at summitracing.com and other vendors) and get the Airlift Load Controller II compressor, and you'd have manual control over your ride height.

 

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2002 gmc envoy_slt
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Discussion Starter #5
Does it hold 50 psi fairly well? I figured it would make the drive a little stiffer if it were at a constant level at all times. Good luck with it though. 5 bucks sounds a whole lot better that almost 500. Good job.
It is at about 47psi right now and it is pretty much the same as before.
 

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2002 gmc envoy_slt
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My understanding of air suspensions is that the airbag/air-spring allows air to escape when going over bumps.....the larger the bump, the more escapes in order to absorb the shock. Have you actually driven over a rough road to confirm the pressure remains within the airbags? (This is the way the ford units in the past have worked and would have guessed the GM system was similar). Obnoxious that the air compressor is that expensive, wonder how hard it would be to wire up a 3rd party like the one listed above to the factory harness to control pressure/hight automatically. Figure that the controller turns it on/off.
 

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2002 gmc envoy_slt
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Discussion Starter #7
I'm assuming the bags just expand out when the suspension is compressed. With my gauge hooked up to it, I bounced up and down on the back bumper and the gauge fluctuated between 47 and 50 psi. I'm pretty sure it will be fine, but only time will tell.
 

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2004 gmc envoy_sle
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My understanding of air suspensions is that the airbag/air-spring allows air to escape when going over bumps.....the larger the bump, the more escapes in order to absorb the shock. Have you actually driven over a rough road to confirm the pressure remains within the airbags? (This is the way the ford units in the past have worked and would have guessed the GM system was similar). Obnoxious that the air compressor is that expensive, wonder how hard it would be to wire up a 3rd party like the one listed above to the factory harness to control pressure/hight automatically. Figure that the controller turns it on/off.
The air bag system is actualy more of a sealed system. Once you add the pressure it stays there untill you let it out, or it slowly leaks out of fittings. The air inside the bag does compress, which is why you can get a good ride out of air because it's like haveing progressive rate springs, the harder you compress the air the stiffer it gets, but on softer bumps it just absorbs the bump with a softer rate.
 

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Good to know

I just bought my Envoy and it has the airbags in the rear. Its good to know that standard size parts and air pressures are used. Thanks. It seems that these compressors over-heat easily, does anyone know if GM has corrected this in later models?
 

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2004 gmc envoy_sle_xuv
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I just bought my Envoy and it has the airbags in the rear. Its good to know that standard size parts and air pressures are used. Thanks. It seems that these compressors over-heat easily, does anyone know if GM has corrected this in later models?

Not for the 2004 XUV. Mine overheats, under inflates, leaks and is more of a Pain in the a$$ then it's worth sometimes. I tow may race-car/trailer all over the Pacific Northwest and every now and then it leaks out while towing and when I power cycle the system to get it to pump up it fails. Then I have to remove all load from the backend to get the pump to work.

-Dual axle trailer and car total 4500lbs
-Tongue weight 300-350lbs

I meet all towing specs and dealer can't find anything wrong :confused:

Warranty is up in 7days so I'm gonna remove factory pump and install a heavy duty after market pump to work in it.

I may just do the 'T' and see how that works out since the 'Voy is used for towing 90% of the time.


Thnx for the 'T' tip,

Rodd
 

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2002 gmc envoy_slt
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I replaced my rear air compressor about 2 years ago on my 2002 Envoy SLT. I only paid $150 or so, bought it NOS on ebay. Still working good :D And I tow regularly...

On the other hand, Ive heard of other T360 rear air ride owners rigging up an aftermarket compressor, sort of the same way the original poster did. Thats great and all, but I am a NUT for OEM stuff. What happens when you go to sell the Envoy? Who is going to want to buy it like that (fabricated because the compressor broke and you didnt want to replace it)?

But to each his own, I actually bought a spare compressor on ebay and a brand new set of air shocks that sit in my basement.

For the rest of you with the rear load leveling suspension:
http://cgi.ebay.com/ebaymotors/Air-bags-bag-and-compressor-Rainier-Envoy-Trailblazer_W0QQcmdZViewItemQQcategoryZ42609QQihZ019QQitemZ290182834210QQrdZ1QQsspagenameZWDVW

Thats a GREAT price for a spare compressor and air bags. I tried selling mine on ebay 2x with no luck :( I would bid $35 on this set and see if you win it! that would be a KILLER deal!
 

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Thanks! This really works!

Thanks for saving me a lot of money. I printed out your "fix" over a month ago when my truck first started having trouble "getting up." Finally a few days ago the compressor would no longer lift the truck at all. It literally had about a 1" clearence in the wheel well and a hell of a low-rider bounce. Since my truck is not exactly new anymore (2002 with 112,000 miles) and i just spent $600 on a new water pump 2 weeks ago, I wasn't too happy about the prospect of paying over $500 to repair a "perk" that i really have little use for. So, I decided to give your clever idea a try myself. I'm happy to report that I fixed it quite easily and i'm not someone who ever works on his own vehicle. I always pay someone who knows what they are doing. Grand total for the repair...$1.98!! Yeah, your tee looks much nicer but i couldn't find that anywhere around my way, so i went to an auto parts store and bought a 7/64" soft (rubber) vacuum tee and inserted the three hoses just as you did, plugged my portable air compressor into the outlet in the cargo area, switched it on and watched as my truck magically rose right back up. I have seen no leakage in the 2 days since i lifted it back up. Thank you so much for your post! And i too apologize the for the book...:thx
 

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2002 gmc envoy_slt
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Discussion Starter #18
Man, last time I was here, I thought this thread was dead. I just recieved your pm mpvkent, but can't find the reply button:eek: to reply to you. I'm glad it saved you some money. We are still using this "fix". I found an air xpress pump at Lowes that fits perfectly in the storage compartment next to the valve in the back. I bought a 6x14 trailer and this "fix" makes hooking it up and ajusting the height for different loads a breeze.
As far as affecting the resale of the truck by rigging it, we got this truck 2 years ago for less than 10k and its almost paid for now. I'm probably going to get my wife a G8 and I'll keep her Envoy for towing and stuff.
 

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2002 gmc envoy_slt
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thanks!

I have had somewhat the same issues.
Back in October the vehicle seemed to lose all the rear air suspension and was riding bottomed out on the rear. I took it to the dealer and they said the compressor was shot and needed replacing (some $1000 approx parts and labor!). At that point I researched it and and read about the various fixes on this forum. Then all of a sudden the compressor seemed to fix itself and ran perfectly until January. Then it started steadily getting lower and lower and until I bottomed out again (definitely not good). Time to fix it.

The original post fix instructions mention 5/32 tubing (that is O.D size) and a 5/32 size T-union. This was the hardest thing about this project, getting this size of T-union, I had to hunt hard for it and eventually go to a specialty commercial pneumatic hose shop for it. I got a nice one with quick connect push-in install of the tubing (less than $5.00).

I removed the defective air compressor unit and installed the t-union.
All the instructions in the original post were helpful and very accurate to dismantle the on-board compressor and the lines. This fix bypasses the on-vehicle compressor and you just top it up or bleed it as needed from the cargo area valve. Then I just pumped it up with my compressor to finish. Awesome fix, especially the price.

I dont work on my car too often but this seemed not too tough a project.

I do have one additional question on this project. What pressure range would the original unit have functioned with? I dont want to over do it and damage/something. In the original post I see mention of approx 50 psi. I started with that number but on my vehicle it does not seem to be enough to achieve the same rear ride height that I had previously. I next pumped it to approx 65psi which looks about right. Would the original on-board compressor unit have pumped to that much? Any comments/answers appreciated.
 

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2004 gmc
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Amazingly enough, the factory shop manual is silent on the PSI involved. But just do the math. Let's assume the air springs are 5" diameter. (I'm guessing because I don't have them)

So the cross sectional area of the air bag is 19.6 in^2. Let's say each spring is carrying 1200 pounds load (approximately the vehicle's weight / 4). So 1200 / 19.6 = 61 PSI.

So 65 PSI is definitely in the right ballpark.
 
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