GRA-2

I have a 2007 (2008MY) 957 TT that has developed an issue with the air suspension, it will drive no problem in 'normal' ride height setting, but wont drop down to 'low' of which in the past I've always driven the car (personal preference).

The compressor sounds like it's running ok and as the suspension will raise to 'normal' height after attempting to be in 'low' I'm hoping the fault is not with the compressor. PASM also seems to be unaffected.

I've had a diagnostic run at a local VW specialist which came up with the following:

08577 - P2181 MALFUNCTION IN COOLING SYSTEM (must be unrelated)

2250 VALVE OPERATING TIME EXCEEDED (this I expected as the compressor will time-out before the fault flashes up on the dash)

1400 CONTROL POSITION NOT ADJUSTABLE
Looking on the internet it seems this may be due to a fault with one of the sensors located on top of the struts(?) I'm also wondering whether one of the release valves is stuck.

Any help/advise here would be very much appreciated..

Something else that has been needing attention is a very slight clicking sounds coming from the front right wheel/suspension area when going over bumps, I've been thinking this is a bush that needs attention and not related to the recent air suspension issue, but maybe worth mentioning..

Thanks
Graham

porschefan931

This may be related to the so called schrader valves. I tried to lower mine with a Durametric and got the same issue.

Apparently they can corrode after a while and don't open or close correctly. Replacing them also fixed my automatic lowering function when the car exceeds 50mph (80kph) and lowers itself for stability.

GRA-2

Thanks, any idea where the valves are located, ideally I'm after a how to guide of some description or some photos.
Do you know if there is a special procedure for de/re-gassing?

GTEE3

I have an '08 CS.
I just had the left Rear release valve replaced.
the way to identify a bad valve is to raise the suv to the top set, then bottom setting.
my left Rear would not fully release.
I could drive in Normal set, but not any lower.

GRA-2

Will give it a go, thanks. I've been afraid to in case it gets stuck in high setting mind!

porschefan931

Sorry i didn't replace them myself the dealer did. When i told them i was trying to lower it, they lowered it for me free of charge after they changed the valves.

GRA-2

Maybe I should have trusted my instinct, the rear axle is now stuck in high terrain! Neither rear left nor right side will drop but both fronts do, seems like too much of a coincidence for two release valves to go at the same time.
The compressor seems to be working fine.
Any suggestions of where to go from here would be MASSIVELY appreciated..
Also, how safe is it to drive on the road using high terrain setting at speeds up to 60mph? Thanks

JAGMAN1

I can't explain how, why, or even if both valves have failed at the same time. But I do know that the air spring pressure holding valves are the part responsible for lowering. Would I drive it like it is? No. I'd park it and fix it myself, or drive it a short distance to a shop. I'd be more worried about stressing a universal joint in the drive shaft than stability.

My experience comes from dealing with my own CTT's issues. I had a problem with the rear end settling after a period of time. I first noticed it after the car would sit for a week. Then it got worse and worse and would occur after just a day of sitting. I replaced both air-pressure holding valves. Did both fail simultaneously? I doubt it. Each valve is fed by an independent air supply from the main air suspension control block. But the system must have some sort of pressure compensation between left and right sides. Anyway...the theory behind this matters very little to you at this point.

Bottom line: You need to replace the air pressure holding valves located at the top of the rear air-spring towers. Yes it's possible that only one has failed, but just get in there and replace both for peace of mind.

I ordered two new valves from Porsche (~$85 each) and a special tool (~$25) from an online shop that allows you to remove the valve. I think it was a vw/audi tool.

I have a pit in the floor of my garage, so I simply drove over the pit, placed two jack stands under the chassis, then loosened the small nut on the pressure holding valves. Air hissed out. The rear of the car dropped 1/2" onto the jack stands. Then I removed the valves with the special tool. Reinstalled. Turned the car on. Closed the doors. The car raised up to normal level (it had only dropped 1/2" onto the jack stands). Then I raised it up one level above normal to remove the jack stands. Lowered it. Done (1 hour job).

Be careful with the torque limits of the holding valve to strut, and then the plastic fill line to the holding valve. The torques were very low 7lb-ft comes to mind. I can't remember the correct numbers, I'll try to dig those up for you.

If you're really stuck and need to drive it. You could release the air pressure to get it down. Might try tapping on the valves with a screw driver handle to get them unstuck too. Just be careful that the car doesn't lower down onto you. Put some jack stands in place that will limit how far it will fall. The added danger is that your arms have to contort a bit to get to the valves. So you run the risk of reaching through a narrow opening to gain access with the wrench, releasing pressure, and then that narrow opening collapses as the chassis drops.

It's an easy job, just be smart with jack stand placement.

GRA-2

Thanks for the input it's much appreciated. I limped the car to a local Porsche independant today and had them hook it up to their diagnostic. Apparently everything points at this being an electrical issue and not mechanical, and they have proposed to replace the suspension control unit for a new one at £600 (910USD) plus an hours labour. I'm very reluctant to pay out for this when there is no guarantee this will fix the problem, and am wondering about fitting a second hand replacement ECU myself. Not ideal I know, as if it doesn't do the trick then I will be left wondering whether the replacement is also faulty, but if it works it would be a lot cheaper than buying new.
My question is, if I replace the control ECU myself (part # 7L0907553J) will I suddenly be able to lower the suspension using the switch in the car, or would it need connecting to a computer first? I appreciate it will need correctly calibrating at the garage afterwards, but want to do all I can to keep the cost down..

GRA-2

One other thing to add, initially I thought this was unrelated but not so sure after reading this:

http://www.6speedonline.com/forums/cayenne-955-957/316151-09-brake-proportioning-ignition-lock-fault-issue.html

I recently noticed a wet passenger side (left side, so drivers in the US) footwell, last night I pulled the drain plug from above the wheel arch liner to find it was blocked and a lot of water came gushing out. The carpet is now lifted and drying, maybe I have a wiring fault due to this leak? There is nothing obvious when looking at the harness any ideas? Thanks again

JAGMAN1

OK, so the presence of a wet carpet does raise a red flag. I would hold off replacing the A/S control unit until you do a full inspection of the wiring bundles in the footwell. I would start with the side that is wet, and then once complete tear apart the other side to double check it as well.

So as to not confuse the LH and RH drive variants I'll describe what you're looking for in vague terms, but understand that my experience is based on a U.S. LH drive CTT.

I had a host of faults appearing on startup that led me down the path of searching for wet carpeting and damaged/corroded wire bundles in the footwells. I didn't end up having any water damage, but did tear everything apart to verify.

Bottom line is this: there is a fuse box that sits atop the battery (Drivers side on LH drive cars) and the wire bundles in that footwell feed into that fuse box. Many of the items that receive power from that fuse box are the various ECUs in the car. A/S is one of them.

Here's what I'd do. Remove the door sil trim on the wet side. Then peel back the carpeting and insulating mat beneath it. You'll see a wire bundle or several. Remove the plastic sheath around it. Then unravel the electrical tape holding it together. You need to expose the individual wires to properly inspect them for damage. Once exposed trace each individual wire from the battery fuse box forward into the floor mat area, then up the front of the footrest area. You are looking for corroded, or damaged wires that are pinch welded. If you find corrosion, I'd clip out the damaged section and then either solder or use a connector to repair the damage.

There are several of these exposed wire splices in this location. If any one of those are wet/corroded then this could cause your problem. Keep in mind that the likelyhood of damage is highest where the water can pool (aka the low point is under the floor mat area).

Once finished on the wet side. Take a look at the other side and if it's dry you're probably good to go. Keep in mind that the carpet may be dry, but the padding material beneath the carpet can remain wet for weeks.

GRA-2

Thanks, I'm not great with electrics but had a quick look at the cables running across the floor yesterday and all appeared ok shall inspect closer tonight. After reading another post (below) I'm wondering whether I will be able to check the live feed to the control unit, I have a multimeter would need to learn how to use it and try to find out which cable to the control unit is the feed. Here's the post:

bowner's Avatarbowner , 10-09-2012 03:45 PM
Hi all new to this site.l would like to share an interesting problem that I had with my air suspension recently,I have a 2004 cayenne turbo that started showing warning air suspension in red on the dash,did all the checks had it plugged in and read, said low voltage changed battery still had the same problem,started tawling the forums posts steered me to the air compressor bought a recon kit still the same problem.After lots of head scratching and armed with a volt meter checked the voltage at the control unit for the air suspension in the boot only had 6.7 volts should be 12.Problem found turns out it is a water leak coming in on the drivers side soaking the wiring loom which had caused damage to the main power to the control unit.Course of action remove carpet,repair wiring loom,seal leak,dry out carpets,reassemble Fantastic everything works no warning lights hope this helps someone

GRA-2

Here's what I found last night

GRA-2

Here's what I discovered last night under the wheel arch!

http://youtu.be/ts9S54j8hAc

JAGMAN1

Looks familiar. I had just as much water and debris clogging mine when I first checked them a few years back. I now include cleaning them as part of my yearly maintenance. I have also removed the rubber drain grommets for the first time this year. I expect that there will be no debris next year when I open the wheel liners to clean the drains.

On to your current Air Suspension issues... Was the foot well under the carpet wet? If so then you need to dig further as I described earlier. Even if you're not great with electrics, this is not rocket science.

Porsche and VW used a really bizarre method of crimping those wires in the bundle in your picture. Essentially when you remove all of the zip ties and tape wrapping the bundles those wires you'll see several (3-6 or so) exposed connections that were made in that vicinity. Those are what you need to visually check and verify that they've not been compromised. Imagine if you took wires and twisted them together by hand, that is what is sitting under the floor. Very very susceptible to damage if they get wet.

If that bundle of wires in your picture were free of splices it could sit underwater indefinitely with no damage; but unfortunately this is not the case.