RAudi Driver

Is it possibly to check and possibly fill the nitrogen if it's reading low. Would there be any tell tale signs that the nitrogen in the airbags, lines and accumulator are in need of a little fill up? I don't drive the car as a daily any longer as my wife too over that duty but I did take it out the other day and it seemed a little more wallowy on some of the larger freeway dips. Maybe it's just me driving a new SUV, but just wondering.

jaystonewee

Scan tool will show system pressure. Or you can use a refrigerant style gauge set and check the pressure tank on the drivers side. Full is 17.5bar IIRC. Check to see if it will lift to full height or if you see the "not possible" error on the display. "Not possible" is a sure sign it's low.

RAudi Driver

The car will rise to the occasion and go to any height in an instant. Doesn't have an issue with the operation of the air suspension. Just think it could ride a bit more taut. I'll break out my tank and guage set over the weekend and dig into it. Have a Launch diagnostic tablet. The pricy one so it should work.

Stay tuned!

YogaYoghurt

The air suspension isn't pressurized with nitrogen. It has a a "normal" air compressor behind the right front tire. System uses normal old air and maintains the pressure in the bags automatically. Not really a "top off" you can do

garrett376

I'm not sure if you're posting in the right forum, because none of that is correct!

Ed, the system VOLUME is what you want to check, not the pressure as indicated above. Read out the measured value system volume with your Launch, and report back. I have a feeling you're just used to a different ride, and all is fine with your 958.

Scott C

I'm not sure why think @YogaYoghurt is incorrect? On my 2011 958.1 CTT, he's absolutely right... There's a compressor below the front passenger door (behind the tire) that refills the system when it's low, and uses 100% normal out-door air. It is specifically not a closed loop system, and you definitely don't need to refill with nitrogen.

https://eeuroparts.com/blog/porsche-...-repair-guide/

In fact, the diag tool allows you to check, bleed, and fill the system entirely - all using the built in compressor w/ outside air.

My last bag failure was pretty big, and I could hear the compressor running until it eventually burned itself out and I had to replace it after I put the new (rebuilt) air-shocks back in.

That said, I'm not entirely sure the OP has a problem - or maybe it's in "comfort" mode and not "normal" or "sport" like he may be used to.

jaystonewee

I'd love to see this writeup of how to check/bleed/fill the system without filling the accumulator with pressurized inert gas first.

Scott C

Make sure it's on a lift, then use the standard "special function" menus in iCarScan or whatever other tool you use to check, bleed, fill. There are several youtube videos for our car, the 955, Audi and VW (which all share the same basic system). YouTube is how I learned to do it. The lift is absolutely imperative, as you cannot/should not even attempt to do anything to the air suspension system with any of the wheels still on the ground.

Here's the Bistine video, which is the one I followed, which only mentions it:
. - there are several others, but that was enough for me to look in my iCarScan and see how to do it (then do it) - pretty sure it's in the "how to replace air suspension compressor" videos too.

My point was, it's not a closed loop system, it uses air, and bleeds/fills itself as the gas expands/contracts with temp/altitude (and if there's a leak). You can fill with nitrogen if you want, but it's not necessary since some of that will naturally be replaced with ambient air (78% Nitrogen) over the course of standard operation. Of course, the argument for nitrogen is to keep the moisture out... but if the compressor adds ambient air periodically, humidified air is getting in anyway. Nitrogen is a contentious topic, I'm only saying that the system itself fills w/ outside air.

garrett376

OK, I guess you can do what you want, but both of you think the opposite of what Porsche says regarding the 958 being a closed system filled with nitrogen. Here it is in their pretty clear words:

garrett376

The 958 air suspension system only ever draws outside air when the system is WAY below a specific set point because a major leak exists to create that condition. It does not do it on a continuous basis as you are stating.

RAudi Driver

Boom evidenced and case closed. Everything else is hearsay.

Whitegalaxie

This is why I only ever buy dealer maintained cars and keep them maintained at the dealer. Not saying there are no good independents but there are a load of not so good ones

Scott C

Never said it does it on a "continuous basis." I said it does it when temps/altitudes change, which cause increases/decreases in pressure, it doesn't have to be "way" below. If you pay close attention when you start the car, you'll hear the compressor kick on fairly often when the weather changes and it needs to refill the accumulator.

And yes, I know what the Porsche docs say - but if it ever draws in air from the outside, it's specifically not a "closed loop" (Taycan Turbos aren't "turbos" either). Moreover, any "minor leak" will trigger repeatedly (w/o necessarily throwing a code) and eventually replace quite a bit of the leaked-out nitrogen with ambient air. My 165K CTT is one of the lucky ones that loves to chew through air shocks, and after working with the dealer repair (while under warranty, in the day) and my local non-stealer shop, I've learned to do the repairs myself. I'm not saying you can't use nitro, just that it's unnecessary. Additional point, the original Porsche docs also say to change TC fluid every 80-90K miles, which we also know is inaccurate.

I realize that nitrogen vs ambient air is a massive debate (in a LOT of car circles, including these forums where it's been stated over and over that Porsche/VW/Audi's air suspensions are not true closed-loop systems, despite the docs). It's so contentious a topic that the FTC has now waded into as potentially being a "scam" service (mostly for tires on daily drivers, but still).Excerpt from (https://www.federalregister.gov/docu...egulation-rule)

Anyhow, my (now) 13yo & 165K mile CTT is worth ~$14-15K right now, $20K tops. It's not going to the dealer for anything but majors anymore (like the 160K service, which cost >$4K) and I'm going to own it/maintain it myself (where I can) until it eventually dies completely. I'm not against anyone who wants to fill their own w/ nitrogen, and I'm sure that the PCar dealers use sealed-tank nitrogen that's humidity free and >74% concentration. I was just pointing out that there's another way, it's built in to the air-suspension system, doesn't have added expense, and that it works as designed.

P.S. Not to nitpick here, but "hearsay" doesn't mean "untrue" it means "second hand (indirect) knowledge." My knowledge is first hand, evidence-based, and empirical. It's not hearsay b/c I'm not reporting what "someone else told me", I'm reporting what I've actually done based on other verifiable reports of how to do it located here in the rennlist forums and several other places on the 'net.

Cheers,
-S