Jeep Garage  - Jeep Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
42 Posts
Discussion Starter · #1 ·
Over the past couple weeks, I had been driving a good amount moving from one apartment to another. I hooked up a trailer and immediately got a service 4wd system message. This has successfully been fixed. A couple days later, I got a message saying immediate air suspension service/repair required. The front of the car didnt have any air in it at all. I took it to a dealer and they replaced a relay and the control module, and then told me there was a leak and it was going to be over $700 to replace the air lines. I picked the car up this morning and what they had said just didnt seem right to me. It will level out in the park position, after about 5 minutes. It will not raise the front one bit, but I can not hear any kind of leaking. It really just acts like it doesnt want to do anything. Im really concerned that it isnt the air lines leaking and dont understand why it wouldnt raise up at all, unless there is a massive leak in the system.
 

·
Registered
Grand Cherokee
Joined
·
4,462 Posts
Is there anyway to check pressures at different points in the system?

Cause when you say the front won't raise one bit, that sounds exactly like a leak in the system. The only other thing I could think is a clog or the solenoid valves failing to open.
 

·
Registered
Joined
·
42 Posts
Discussion Starter · #3 ·
I do not have any way to check. Ive been reading about this some, and they did not say that they tried to test any of the pressure or if they had tried to refill the system. It should be nitrogen filled, and pull outside air in to compensate very little. From what I was told by the mechanic there, he made it sound like it is completely air filled, and the compressor should be able to pull air in to fill the system when there is no leak at all.
 

·
Registered
Grand Cherokee
Joined
·
4,462 Posts
You probably know more about than me, what little I read, its an air compressor, filling a bottle and the bottled pressure goes to a control block of solenoid valves that are computer controlled to open and close the valves to send air pressure to the air springs.

I did not know the system was serviced with 100% nitrogen, and from what you describe, the compressor must be between the bottle and the air springs. And the system must top itself off with air from time to time.

BTW, air is 80% nitrogen. Sure 100% nitrogen is better for a bunch of reasons, but its not like air is that bad in comparison. Its pretty common for a lot of things, even tires for cars, to service with 100% nitrogen if its available for better performance and then top off with air as needed, instead of going to the extreme inconvenience and extra cost of topping off with nitrogen.

And its more important, you get better benefit, making sure its "Dry" air or nitrogen. i.e. moisture in the gas has far more performance and reliability degraders than using air over nitrogen.

But back to your problem, logically you could have a leak or malfunction of the solenoid valve block, that is why pressure is not getting to the front air springs. Sure a clog would be possible, but you'd would have noticed before when the air springs were up and wouldn't lower, so I say that's less likely than a leak or failed/stuck valve.
 

·
Registered
Joined
·
42 Posts
Discussion Starter · #5 ·
I know very little about the whole system so I really doubt I know more than you about it. They said they had found a leak, and that they believe that is what is causing the other problems. My biggest question is if there is a problem, why can I not disable the system as you would if you needed to jack the car up (by holding the up and down controls down at the same time)? I would think that this should be able to be done no matter what, unless I am just misunderstanding exactly what those controls do. Also, when I took the car in to be looked at, it had been operating fine, and just cut off. Why would the leak have gotten so much worse that now it wont function at all?
 

·
Registered
Grand Cherokee
Joined
·
4,462 Posts
Cause leaks work that way, sure they may start slow and grow worse over time, they can also just start and be bad enough right away to be a disabling problem immediately.

You're talking enough pressure to raise and lower a car, that is enough pressure to blow something out to be a huge leak. Not to mention, I'm not convinced you just don't have a failed valve that isn't opening to raise the front. Unless the dealer checked that and confirmed the valves were working right and didn't describe it well enough to you for you to pass it on in your post.

High speed handling is a huge thing in modern cars, there are safety standards set by law and government, there has been huge lawsuits over cars that can't handle as well as a stupid ignorant driver would expect it to handle. The springs are huge factor in that handling, as well as the suspension travel, stance, ride height, etc, etc....

That is the whole reason Jeep put in the Air Suspension, they couldn't get the extra off-road ability they wanted and still pass all those high speed handling regulations and also make the car as smooth riding as the market demanded. They had to put in an air suspension that changed the spring characteristics for the particular condition at the time. And the computers control it, so some idiot driver doesn't try to drive it like a Corvette at 90mph with it set at the highest ride height. The system will lower the car and change the spring rates when you hit a certain speed, where if you were an idiot might do something stupid to go out of control.

I suspect, and have heard some info confirming it, the system is designed as fail safe. If it fails, it will do so in a safe mode. That it even if all the gas leaks out of the system and it bottoms out, there is enough spring rate still left in the system the car has at least a somewhat functional suspension.

And that's the thing, just like the check engine light, if the car isn't meeting the regs by the Federal Government, it has to be repaired, and thus they require the nagging light to push the owner to get it repaired.

So you're JGC may seem to be riding fine, but if the Air Suspension has failed, it might only meet the high speed handling characteristics of a 2005 vehicle, and if you did something really stupid or panicky at high speed, you might roll it over, thus the light on insisting you repair it. (That's a hypothetical, I really don't know, it really could be other reasons and it might be more dangerous than I'm speculating).

We are living in the era of the NHTSB issuing a report saying Jeep's new shifter is not great and its possible to miss going into park if you attempt it just by feel alone, admitting that a driver would have to do dozen things wrong, and ignore a dozen warnings that something is wrong, but there are some drivers that totally stupid and careless, so therefore, we're demanding a recall that will cost you 10's of millions of dollars to change the system so the car figures out if the driver might want to get out of the car and shifts itself into park.

So yea, when the gov regs says something is dangerous you can't always trust just how dangerous it really is.
 

·
Registered
Grand Cherokee
Joined
·
4,462 Posts
I haven't tried this particular App, I have tried others before, and the ones before are sorely disappointing. They claim to do all sorts of things, and people rave about them saying they can do everything you need.

Then you actually check them out and find they're nothing more than a generic OBDII scanner with a few data monitoring abilities. They can't do 1/10th of what a real DIY'er would need, nor 1/50th of what the dealer tools you don't have access to, can do. And then the folks that rave about it, when you challenge them on their crummy advice, it becomes quite clear that they don't know their butt from a hole in the ground when it comes to auto diagnostic tools, they were simply wow'ed by what a neat toy it was.

I use AutoEnginuity, and it is expensive and it is limited, but by far exceeds any of these so called wonder apps you can download on your phone and claims to tell you everything you need to know diagnostically.

I have no idea how good diagfca app really is, it does claim a few more "capabilities" than the previous Apps I've checked out, but it seems a lot like them. I advise them that if they truly are as good as they claim, then they need to revamp the marketing on the website, because its the same vague, but fantastic claims as every crap piece of app using the same marketing before them. So they are only making me suspicious its just the same as the others and will be a total and utter disappointment and waste of money for someone that needs can and needs to do serious diagnostics.

Can it scan for "C" and "U" codes from subsystems on the CanBus? Can it initiate common and routine maintenance procedures over the CAN Bus, like activating ABS Pumps, Emission Pumps?
 

·
Registered
2014 Summit 5.7 4wd 20" tires swapped to 18", added all skid plates
Joined
·
2,576 Posts
I know very little about the whole system so I really doubt I know more than you about it. They said they had found a leak, and that they believe that is what is causing the other problems. My biggest question is if there is a problem, why can I not disable the system as you would if you needed to jack the car up (by holding the up and down controls down at the same time)? I would think that this should be able to be done no matter what, unless I am just misunderstanding exactly what those controls do. Also, when I took the car in to be looked at, it had been operating fine, and just cut off. Why would the leak have gotten so much worse that now it wont function at all?
My understanding is that it's nitrogen filled and is a closed system. Which to me would mean that there is an accumulator somewhere to hold whatever "excess" nitrogen is in it that isn't needed at any particular point in time and space. When it needs more nitrogen to pump up a strut it pulls it out of the accumulator. When it wants to lower the car it pulls the nitrogen out of the strut and pumps it back into the accumulator.

If it has a leak then it's likely going to wind up short on nitrogen and simply would not be able to pump things up when called upon to do so. I'm not sure it's possible for it to actually draw in outside air, even if there is a leak due to what I would guess to be a substantial difference in pressure between the nitrogen, which I presume it highly pressurized, maybe 50 to 100 psi, and outside air, which is at a relatively low pressure of 15 psi.
 

·
Premium Member
Joined
·
1,478 Posts
2014 fsm:
the air suspension is a closed type system that does not draw in fresh air during vehicle lifting or leveling. Instead, it moves pressurized air back and forth between an air suspension reservoir and the four air springs as required to raise or lower a specific corner of the vehicle. The air suspension compressor assembly includes an air suspension valve block, controlled by the ascm. The valve block isolates and actuates the raising and lowering of each pressurized component using individual air lines for the air springs and reservoir. The air suspension compressor does have a filtered air suspension hose assembly for adding air volume if a component of the system loses its air pressure and is replaced. The compressor is not intended to replenish the entire systems air volume. There is a procedure for complete system fill using an external source if it is necessary; however, this should only be necessary if the air suspension compressor or air compressor valve block is replaced.

Refilling the system: If the air suspension system is fully depleted of air it can be refilled using a scan tool and air suspension refill tool - tool, air suspension refill 10247b which is used with a nitrogen supply tank (can be acquired at a local gas supplier). The nitrogen must be purity class 5 (99.999% pure). The size and volume of the nitrogen supply tank will determine how many air suspension systems can be filled.
 

·
Registered
Grand Cherokee
Joined
·
4,462 Posts
My understanding is that it's nitrogen filled and is a closed system. Which to me would mean that there is an accumulator somewhere to hold whatever "excess" nitrogen is in it that isn't needed at any particular point in time and space. When it needs more nitrogen to pump up a strut it pulls it out of the accumulator. When it wants to lower the car it pulls the nitrogen out of the strut and pumps it back into the accumulator.

If it has a leak then it's likely going to wind up short on nitrogen and simply would not be able to pump things up when called upon to do so. I'm not sure it's possible for it to actually draw in outside air, even if there is a leak due to what I would guess to be a substantial difference in pressure between the nitrogen, which I presume it highly pressurized, maybe 50 to 100 psi, and outside air, which is at a relatively low pressure of 15 psi.
The tank or accumulator is behind the rear seats, in a nook in the floor pan. At least that is what I see in the diagrams.

Your tires are closed systems, yet they need to be serviced from time to time. Sure they don't have accumulators, and often its the change of season bringing on colder temps that requires adding air to bring back up pressure. BUT, there is diffusion, where the air molecules under pressure force their way through the rubber molecules structure and slowly leak out. That is the biggest reason why you need to add air from time to time to your tires, they actually do loose the gas compressed within them, even if they have no leaks. I can't imagine this air suspension is any different and the Rubber Air Springs aren't that much different than tires.

So I tend to believe the O.P.'s dealership, when they told him the system is charged with nitrogen at the factory and will service itself with air as needed. Otherwise we would be seeing a lot of posts complaining about the ridiculous prices the dealerships are charging to service the Air Suspension with nitrogen when the warning light goes off on the dash.

As well, the O.P. says the rear changes ride height, the front will not. I would think if it was a matter of low charge in the tank/accumulator, then front and rear would raise and lower, just not raise to the highest height. I suppose for some reason they may have the system set up to raise the rear first, or exclude the front for a lack of servicing, but I'd also suspect that as unsafe.

I'd have to agree with the dealer, the most likely reason the front won't go up and down, while the rear will, is there is a leak to the front air suspension, or I added, there is a solenoid valve body, its possible it failed and won't open valves to let the front go up and down. You can't rule out a clog, but I suspect a clog won't let the system go up, then it wouldn't have let it down. So, I'd put a clog in the system at the bottom of the list as a possible.
 
1 - 11 of 11 Posts
Top