Finding Leaks in G67 Air Suspension

In the past couple of weeks I've noticed the air compressor for the G67 auto leveling suspension in my 96 RMW has been kicking on about once an hour when it's parked. It works fine otherwise. I assume there's a small leak somewhere. Could be the line from the compressor to the rear, the lines to the shocks, or the shocks themselves. The car has 84k miles and it looks like they're probably the originals. I imagine it'll eventually get worse and start wearing on the compressor and battery. So how should I go about finding the leak? Soapy water?

I see that Rock Auto has an AC DELCO kit #504110 (GM # 19178430) shocks, lines, and hardware for about $140. Should I just go ahead and replace them because of the age and mileage just for the peace of mind?

It is a 97% chance that the bags in the shocks are cracked and leaking. I would just get the kit from Rock Auto and replace them, it will save you a lot of time and effort. If you must troubleshoot, a bottle of bubble liquid for kids would work. Put it in a squeeze bottle and squirt it on the suspect parts.

I kinda assumed the shocks were the prime suspect. It was an estate vehicle and hadn't been driven in over a year when I got it. Now that I've put some miles on it things are starting to crop up.

I price checked the AC part number elsewhere on the web and found that Amazon has then for $20 less. One of the two reviews there is 5 stars: the other is 1 star. He said that this kit is just a set of Gabriel Hi-Jackers with an AC Delco sticker on it. Comparing photos on Rock Auto it certainly appears to be the case. The Gabriel's are $90 a set. I don't mind spending the money for a high quality part that's a direct fit, but it looks like the line kit is smaller on both types and might need an additional kit to adapt it. It also looks like the air fitting out of the side of the shock points a different direction than stock.

Can you recommend a good set of shocks? Nothing too fancy is required...it's just a family truckster.

There are a half dozen that are similar. It depends on what ride you want. Gabriels are good, Bilsteins, and a couple of others are all good. You can get heavy duty shocks that will make the ride a little more controlled. The air shocks can be installed with a fill valve if you do not want to plumb the automatic level system. I have heard that installing the Gabriels is not all that big of a deal, just reroute the hose a little, and use the correct fittings. The autolevel is a neat system to have, in case you haul something heavy once in a while (you will find many uses for the cargo hold). Get a set of all four shocks of a matched type, so you do not have weird handling characteristics. The fronts have the single bolt going straight up, and is easy to bend back and forth to break it off instead of fighting with the nut to get it off. I would also check with "Navy Lifer" on the impalassforum.com for a set of upper U-bolts for the rear shocks. They make it a lot easier to install them.

For what it is worth, for a few dollars you can install a 9C1 front anti roll bar, and a Ford Crown Vic rear bar (21mm or larger preferred). I got a used front from the local pick-n-pull for about $20 and another $20 for new standoffs. The CV rear was the same price for the parts but I had to buy 2 heavy duty muffler clamps $6, and a pair of bushings with mounts for another $20. The rear bar bolted in like it was made for the car. Installing them will not affect the softness of the ride, but will make cornering much more pleasurable.

Thanks Fred. I plan on retaining the auto level system as it still works and it's no hassle to adjust for the occasional heavy load. I also plan to do the front shocks at the same time as the rears.

The ride is decent, but could definitely be firmed up some. It's a bit wishy washy at times. Just this past weekend I drove it up to the lake house and it was undulating on some of those country roads. I've been looking in the yards for the large Ford/Mercury rear bar, but haven't found one yet...just the smaller ones. I haven't investigated the larger 9C1 front bar, although that makes sense with adding a rear bar. I assume it's a direct swap once you change the frame bushings to the larger ones?

I think I screwed up. We were planning a trip out of town last weekend so the Tuesday before I bought new air shocks from AutoZone. From sing a little research beforehand on RockAuto I asked the parts guy if there was an adapter kit to hook it to the factory compressor. Oh no everything you need is on the box. I got them home and on the hardware package it listed a part number for another line kit to hook it up to GM on-board compressors. Of course nobody else in town had one in stock. So I ordered the kit and it came in Thursday evening. Since we were leaving Friday morning I held off on changing them out.

So last night I started in on it. I found the fuse for the compressor and it was blown. Come to think of it I hadn't noticed the compressor kicking on every so often for a few days. Anyway, I ran the new lines. I didn't hear any air come out when I disconnected the original lines. Changed out the shocks. (Thanks GM for the excellent top mounting bolts.) Put a new fuse in....and nothing happens. I'm afraid the compressor finally had enough and locked up.

So, is it even worth trying to test to see why it isn't working? If it's bad where can I find a good one? I really don't want to change out the shocks again. I suppose I could install a manual fill valve, but I really liked the auto level feature.

Also, what other cars use have an interchange compressor? Fleedwoods? Caprices? Roadmasters are scarce in the yards here but Fleetwood abound.

The 94-96 cars with automatic load leveling all have the same compressor. The FW may have one as well, if it has automatic load leveling.

Thanks. A little bit of searching informed me of the same. It also sounds like earlier compressors will work but might have to change the bracket and the wiring plug. I thought about all those FL's I saw in the yard last time and I think they're the later type. If I can't find a working one on here there's a $500 95 180k mile Fleetwood here locally with reverse blown out of the transmission and some body damage. I might try to get that if the compressor works. Maybe it could be parted out for the engine and break even on scrap.

This compressor deal really has me bummed. It's a classic case of "for want of a nail the shoe was lost".

And people wonder why I hoard parts.

If the 95-96 Fleetwood air suspension pump is compatible with the RM & RMW, then ebay has a few I think and if the 94-99 DeVille pump is interchangeable there are even more options.

Fred Kiehl wrote:

And people wonder why I hoard parts.

Fred,you don't hoard parts you BANK them for the rest of us and I'm glad you do.

I made some headway with my compressor situation. I found that the black wire with the green stripe is power to the compressor, and the black wire is the ground. I jumper wired it and what do you know it still works! So, I thought maybe the relay was bad. I powered the 30 and 85 terminals, grounded 86, and tested 87. I hear it click and 87 gets 12v. So it looks like the relay is good too.

This leads me to two possible causes of the suspension not airing up. The first being the axle switch is bad. I'm going to try to test it. Looks like there's two circuits. One pair of wires that switches the relay on, and another pair that control the dump solenoid. The other possibility, and I hate to admit this, is that I never turned the key on when I hooked it back up. I've heard the compressor come on while parked so I assumed it was always active. Maybe the key needs to be on after all. I've also learned that there is some sort of time delay function with the axle switch to prevent it from activating over every little bump. So when I manually moved the switch arm up maybe I didn't leave it there long enough.

If it turns out to be the key, does anyone have a dunce cap I can wear for the week?

Any particular color,I have a bunch of those dunce caps and hope you don't mind that they are all worn out?

Color isn't important as long as it fits under my thinking cap.

I don't know if turning the key on will work, but the idea came from reading something on another forum for Escalades and Tahoes. The common thing when they start to fail is the rear end sags overnight, then when they turn the key on the compressor runs for 30 seconds or so to fill it back up. If it does work the next question will be why was mine kicking on while parked with the key off.

It is designed to kick on for up to a certain length of time, once with the key off and then not again until the key is turned on again. At least that is how I read the service manual. Mine was kicking on due to a slanted driveway and I removed the fuse. It would also kick on when level if I got into the car through the tailgate, but once it turned off then it wouldn't work again until the key was turned on.

Update:
I changed the rubber hoses on the compressor as they were disintegrating into powder. I reinstalled everything and jumped the terminals to get some air into the system to check for leaks before dropping it on the ground. Then I turned the key.... I'll be needing that dunce cap in a 7 5/8" please. I really need to find a set of factory service manuals.

I also found out another reason that my ride home from the camping trip was so wishy washy. Both sway bar links were broken. Must have just happened as I didn't notice it when I changed the oil and lubed the front suspension before leaving. I changed them out too and wow what a difference! Definitely inspires more confidence dodging pot holes and tire gators. Next up is determining what front shocks will best match the Gabriel HiJackers. They look decent but are borderline on the fender bounce test.

When I get this egg off my face from the compressor debacle I'm going to write up replacing the factory air shocks. I have a few tips on removing the top bolts and routing the new air lines that might save the next guy some trouble. Thanks for all the help and offers on my chicken little compressor.

The saga continues...

I put the kids in the back seat the other day and I heard the compressor kick on (key off). Seemed strange as they only weigh 65 pounds between them and they were in the middle seat. I thought maybe there was a leak so I jacked it back up and sprayed all the fittings with soapy water. I didn't find any.

With the factory shocks I could put a knee on the back bumper and feel the car rise as the shocks pumped up. I haven't been able to feel it with these shocks. So I turned on the key, dropped the tailgate and measured to the plastic lip then I sat on the gate and it dropped about 2 inches. I was expecting the compressor to kick on after 20 seconds but didn't hear anything. I checked the fuse and it was blown again. I replaced it and measured again. It never raised the back end back up, although I could hear it running.

When I had the compressor out I checked to make sure it was actually pumping air by rubber banding a balloon to the outlet and jumping it. It blew it up just fine. Granted,  the pressure to blow up a latex balloon is no match for the air shocks on a 2.5 ton B-body behemoth.

So, I'm back to thinking the compressor isn't quite up to snuff, although it is running and pumping. The other possibility I've been pondering is the shocks themselves. The factory shocks' top mounts are fixed to the outer tube, and all movement is at the bottom. These Gabriel shocks have the piston rod attached to the top mount, and the air bladder at the bottom inside a tube shield. They have movement at both top and bottom. The middle of the shock body kinda floats between the mounts. I wonder if this different design had something to do with it. It definitely makes hooking the air lines up more difficult as you have to account for movement of the line, whereas the factory shocks don't. Monroe makes a Max Air shock absorber that have the bladders exposed at the bottom like the factory shocks. I do not know if the top mount just spins for alignment, or if it too is connected to the piston rod. For what it's worth the currently  available AC Delco replacement shocks appear to be Gabriel HiJackers.

Not sure where to go with this. I'm leaning towards finding another compressor and swap it out. I'd also like to check out the Monroe shocks just to see how they're built. I'm assuming that the compressor is blowing the fuse because it's continually running when I'm driving it. It's easy to check as the under hood light shares the circuit. I'm also tempted to just turn it into a manual fill system and be done with it, but I'd really hate to abandon the self leveling feature if at all possible.

What a mess! Finally got this all sorted out. I've been waiting a few days to update until I could watch it for a few days. This will be lengthy, but will probably save the next guy that wants to keep the self leveling suspension a LOT of time and money. One of the things I suspected from the last post was what caused all the grief. Caveat Emptor!

I thought maybe the compression nuts were too tight and collapsing the hoses and preventing air flow. So I disconnected all the lines to inspect them and found nothing wrong. I tested all the lines and connections again for leaks and found none. It still wouldn't raise the wagon with a load in the back.

Back to the compressor: After a lot of digging in the junkyard I found that '97-05 Chevy Venture vans and their siblings (Pontiac Transports and Montana's, Oldsmobile Silhouettes, Saturn Relays, and Buick Terrazas) use a compressor that it's very similar to ours. The good news is they're very plentiful and newer than any of ours. They're also easy to access behind the rear wheel. The bad news is they're just as likely to be have busted air shocks and blown compressors by the time they reach the junkyard. They're also much crustier than ours because of their mounting location.

They need two modifications to work. The air intake hose filter canister needs swapped. Also, the exhaust nipple on the air dryer is larger on the van compressor than our RWD compressors. You can either swap complete dryers, or just the dryer top, if the "new" one is in better shape. FWD dryers use the small nipple too BTW. The electrical connections are identical.

I found 24 potential vehicles in the junkyard, and 13 of them had compressors. I found that some compressors were obviously junk as they would not blow any air. Some were weak and would barely blow up a balloon. I found a couple that seemed to blow up a balloon quicker than the others. These were the ones that still had air shocks installed on them. I took one of these home, swapped dryers, and installed it in the car. It would air up the suspension and shut off. However, it would not raise the vehicle back up enough to shut down the compressor with me standing on the bumper. I exchanged that compressor for another "good" compressor from the junkyard and it did the same thing.

I thought that these compressors, while better then others, might be just worn enough to  not be able to build the required pressure to raise the vehicle with a payload. I found that new compressors for Venture vans were still available for $250 form Arnott-part # P-2586. Salty, but not $700 GM salty. I called the manufacturer and talked to their tech guy. I wanted to know if they sold the small nipple dryer separately. They do not.  I then asked if the threads in the air dryer top were the same as the OE parts, so I could swap them and use the new dryer with the old top. He told me that they only manufacture shocks and struts. These compressors were a large lot buy-out from GM's original equipment supplier. So they should fit but, he couldn't say for certain.

I ordered one from an online retailer. The next day the retailer called to say that the manufacturer has them on indefinite back order. They refunded my money. I looked them up on Arnott's website again and they now listed them as out of stock. I think my call that day before led to updating their inventory. I made several calls and found that most retailers don't stock them, but order them from the manufacturer when you place the order. I finally found a company that had one in their own inventory. After it was delivered I compared it to my original compressor and the construction details are uncanny. The tech guy wasn't BS'ing me. I made the required changes and installed it. It still wouldn't raise the vehicle with me one the tailgate. WTF!!!

So the compressor is new, runs quickly and quietly, no air leaks in the lines or shocks, and no collapsed lines. Air lines even hold pressure for 5+ days with the fuse disconnected. So by the process of elimination I came to the conclusion that it can only be the design of the Gabriel Hi-Jacker shocks.

I ordered a set of Monroe Max-Air MA-717 air shocks. Don't let a parts store sell you MA-819 as they are for spec'd for sedans by Monroe. The parts store listed both with no differentiation. The extended length of sedan is 3" more than the wagon according to Monroe. The extended length of the 717's match my old ones. These do not have the shielded bladder like the Gabriel's. They do not have the "floating" tube in middle, or swiveling top mount. In fact, they appear to built pretty much identical to the GM shocks, except for the single screw on type air fittings. I have no idea why AC Delco apparently choose to relabel Hi-Jackers instead of these.

I replaced the Hecho in Mexico shocks with the Made in the USA shocks (that actually cost less!) and wouldn't you know it, the damn thing works!!! I even tested it by putting 4 people (approx 800#) on the tailgate. The compressor kicked on, raised the wagon, and kicked back off just as its supposed to. Even with the brand new compressor the Gabriel's wouldn't raise enough to shut the compressor off with just me standing on the bumper (240#). It's been 3 days now and I have yet to hear the compressor kick on at random when I've been out in the shop. If I go stand on the bumper it kicks on (key off) after 20 seconds or so. Walk around to the driver side front tire and I can hear the compressor dump the excess pressure about 20 seconds after I get off the bumper.

Maybe those "weak" compressors from the junkyard weren't so bad after all. In the process of switching and testing I discovered that the dryer on my old compressor was very wet inside. It had obviously been wet for a long time. The check valve on the inlet side was rusted. Even after I swapped dryers my original compressor would still leak down after a couple hours. I think the exhaust solenoid or valve in the compressor head was damaged by the excess water in the dryer. So the original one was bad, but the junkyard one should have worked with the correct shocks.  New ones are still available, but I suspect the number of them left are dwindling. If you want one, better find one now.

There's a coil spring included with the Gabriel GM self leveling kit. It goes inside the air dryer to boost the residual line pressure value from the factory 14-17psi to 25+ as indicated.  Monroe says theirs need 20psi minimum so I left the Gabriel spring in the dryer. That kit also came with a nice union that came in handy to splice the original long line to the new rear lines.

There's one other thing I should mention. I test drove the vehicle twice with the Gabriel's. Both times I'm sure there was air in the system when I left the house. It's possible though that on the second trip it could have leaked out when I stopped for a few hours via the malfunctioning original compressor check valve. So they could have been damaged from that. That being said, I don't think the shocks were damaged. I suppose they could have been defective out of the box though.  I tested it for raising the vehicle before the first trip and it wouldn't shut the compressor off then. The second trip was only about 10 miles back after the stop, and probably not long enough to hurt much.

I forgot that I took pictures when I was going thru compressors.

Top is original compressor in the bracket. Bottom is new Arnott compressor. The green thing at the upper left is the intake filter that goes thru a body bulkhead  on the van because of the mounting position behind the rear wheel. Swap it over to the 35mm film canister looking filter from the original setup. The rubber hose needs rerouted slightly too.



Dryer outlets. RWD and most FWD on left. Larger nipple Venture van on right. Tops unscrew to change. I had to use a vice because I didn't have a wrench large enough. It should go without saying, but make sure the nipple it's pointing up when you remove it.



Dryer guts. There's a check valve toward the compressor, then crystalline dessicant, a foam pad, a cotton pad, steel spring seat, residual pressure spring, another steel seat, then a rubber flap check valve, then the top with nipple. Pretty obvious that this one has been soaked with moisture for a long time. I used this top on the new dryer assembly, along with the Monroe spring to bump up the residual pressure.



All Swapped and ready to go. All electrical connections are exactly the same between vans and B bodies.

Old thread, but pertinent to the factory leveling system.

Does your experience conclude that the factory compressor will work OK with the factory-type shocks , but not Gabriels with the enclosed bladder?

You can hook the system up to any air shock. The level switch will cause the shocks to lift the car to the determined height, and release pressure if it is too high.

Fred Kiehl wrote:

You can hook the system up to any air shock. The level switch will cause the shocks to lift the car to the determined height, and release pressure if it is too high.

That's what I would expect, except that the OP said he could not get the system to raise the car with his new pair of Gabriel shocks, but replaced them with Monroes and all worked OK. I also remember reading somewhere that there were two different springs for the compressor for the different style air shocks.

I've already got the Gabriels, but don't want to install them if the compressor can't handle whatever the difference is.

Wouldn't an aftermarket compressor be just as affective? They're small and would probably fit in the stock location.

The wiring may be an issue.

Wiring should be straight forward. You'll have to ditch the stock connectors though.

The FIRST thing I do on my whale wagons is replace the rear springs with variable-rate Moogs and all four shocks with KYB Gas-A-Justs. The rear springs and four shocks can be sourced from Rock Auto for cheap. Then just tuck the air lines up out of the way in the back, pull the compressor fuse, and BE DONE.

My 96 Roady Wagon has had this setup since 2008, and I also did this on my '92 Custom Cruiser wagon. One of my favorite cheap, easy (other than the upper bolts on the rear shocks), and BEST mods. I'm about to do the same thing to the 78 Electra Wagon project.

Rides great with the MOOGs and the KYBs, still tows a boat fine, handles a full load of people an cargo, and I never again have to worry about shock or hose leaks, ride level sensors or compressor failures. All these components are just too old now...either worn out on the high-mile cars or dried-out on the low-mile cars. It's NOT worth the effort!

Rock Auto Parts and Pricing -
MOOG Variable-Rate rear coil springs, Part # CC623 - $48.79 pair
KYB Gas-A-Just Rear Shocks, Part # KG5504 - $29.89 x 2
KYB Gas-A-Just Front Shocks, Part # KG4515 - $33.79 x 2

DONE....forever.

-Texas Mike