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The Jeep has once again been behaving as of late...no issues with any of the height levels and no odd noises....

Any reason to get a Scan Guage vs Scan Tool...does one offer more or less than the other...I definitely want to have better insight into what the suspension is doing on a daily basis....
 

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Like filling tires with nitrogen, nitrogen retains pressure over temperature changes and leaks less, you should see no drop.
I have often heard this said but it is false, nitrogen is a perfect gas, like oxygen, and therefore respects the same law of physics:

PV = nRT

Where:
P = pressure
V = volume
n = number of gas molecules
R = universal perfect gas constant = 8.314 .......
T = absolute temperature in Kelvin

Nitrogen leaks less than oxygen: not completely wrong but negligible, the diameter of a nitrogen molecule is 0.315 nanometers and that of oxygen is 0.29....

The advantage of nitrogen over air therefore only concerns the risk of corrosion.

I have read that it is the compressor which creates the vacuum in the various elements before filling them with nitrogen; a compressor is not a vacuum pump and therefore cannot create a very high vacuum, so there are necessarily some oxygen molecules left in the circuit and under these conditions what is the point of using class 5 nitrogen to 99.999% purity which is much more difficult to find than industrial nitrogen class 4 at 99.99%?

Thank you for the answer.
 

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I dunno, I don't observe nearly as much truck, aircraft, Jeep, car tire pressure variance based on tire temperature when they are filled with nitrogen. I rarely refill a nitrogen filled tire where plain air tires often have a slow leak. The math doesn't seem to support the observations... :smile2: Worth the effort can be more subjective.

The nitrogen gets diluted by the air/oxygen remaining in the system, so its filled with purer nitrogen to compensate. The compressor pulls in air to makeup for loss and leaks so it gets further diluted. Nitrogen is there primarily for corrosion and ice prevention and the purer it is, the better it works. We can guess that someone at Jeep or Mercedes traded off durability vs the pain of dealing with high grade nitrogen and compromised on this approach. But that trade is probably based more on shop environments, not the home DIY'er. Mercedes has long been plagued by corrosion in their are suspension valve body. There are shops in Europe that make a fine living rebuilding them, perhaps they overcompensated.

If you are looking for rationale to use less concentrated nitrogen, some here just fill with air. Not sure if those Jeeps are kept long enough to matter and just pass off the problem to subsequent owners... or it just doesn't make that much difference in the end.
 

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In fact, my problem is that the JEEP dealership equipped to fill the nitrogen system closest to my home is located more than 200 km away, the other three which are closer are not equipped for nitrogen !!!!:frown2: This means that I will have to do 400 km and lose a day just for filling.
Already having the connector for the air conditioning system which corresponds perfectly to the filling nozzle of the tank, I made a quick filling with compressed air to only 9 bars (the maximum pressure of my compressor) and everything works, but I would now like to do a complete filling, at the correct pressure and with nitrogen to avoid corrosion.

So all I need is a nitrogen bottle, a pressure reducer and a scan tool such as alfaODB to be able to do it myself. But if it is easy for an individual in Europe to buy a small bottle of class 4 nitrogen with a pressure regulator for around 150 €, it is much more difficult to find class 5 nitrogen rather reserved for professionals and available only in large bottles.

You answered my question by telling me that the compressor compensates for any losses with air, the extreme purity originally requested is therefore illusory.

Thank you very much for your reply, that solves my problem.:cheers2:
 

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Provided you have no leaks, there is no dilution of the dry nitrogen fill. The system only draws in outside air to compensate for a loss. I would not attempt to evacuate the struts with a high vacuum pump. You'd have to pull down below 500 microns to remove all possible moisture and they were not designed for negative pressure. If you are concerned you may have moisture in the system now, I'd do more of a fill/empty cycle a couple of times.
 

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Don't take me wrong, I think there are both some performance and moisture protection compromises when using less pure nitrogen. My point was that there may be already enough air/moisture in the open system that the nitrogen fill will diluted enough to perform poorly if you start with less pure nitrogen.

If you pull a vacuum I'd guess the rear bags will deflate enough to pull away from their seats and either tear, pop out, or both.

If contamination is suspected or of concern, they would deflate the system to atmosphere and then refill a couple times to flush it out. With less pure nitrogen, the Air Mass calculation routine is going to be off a bit.

The make up hose contains a filter with descant to remove moisture.

I think the better grade nitrogen is only available in large bottles nearly everywhere.

I dunno how much of a chance you will take, but the "The nitrogen must be Purity Class 5 (99.999% pure)" statement is everywhere in the service manual. I don't see anyone recommending a compromise.

If you have RAM truck dealerships in the area, they can fill Jeeps. Their air suspension is nearly identical.
 

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To echo what ColdCase said, I would be leary of trying to pull a vacuum on this system. It was designed to hold positive pressures. I have my doubts that the engineers thought about whether every seal, o-ring, reed valve, airbag bladder, poly line, fitting could handle a vacuum.
 

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I was concerned that all the system were not designed to withstand negative pressure; but since the compressor is supposed to empty the various components before filling them with nitrogen, I still asked the question.
I will therefore only make a deep but rapid vacuum in the tank.


Thank you for your answers.
 

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Finally I bought a class 4 nitrogen bottle + a pressure regulator for 130 € on Ebay in Poland:
[url = https: //servimg.com/view/18111406/1543] https://i.servimg.com/u/f94/18/11/14/06/20211210.jpg [/ img] [ / url]

I bought AlfaOBD to have access to the ECU controls of the suspensions and I filled the system with nitrogen myself after emptying the tank with a vacuum pump each time after the compressor deflated each spring .

Everything is working fine and the future will tell if I was right or wrong.

End of story ................................ I hope.
 

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20211210.jpg


The links didn't work for me. As an experiment, I just dragged and dropped the image. Seemed to work.
 
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