Is Nitrogen Required For Air Ride Repairs?

Looking over air ride service information from several OEMs like Tesla, Dodge and Mercedes, they recommend refilling the system with nitrogen gas if a component has been replaced or the system has lost integrity. This might seem like overkill, but sound scientific reasoning is behind this recommendation.

The tool to fill the system is usually a simple setup with the correct fittings for the tank and port on the vehicle. The tool also will use a pressure regulator to set the pressure in the system. With the assistance of a scan tool, these tools replenish the reservoir to a recommended pressure.

The air we breathe is already 78% nitrogen, 21% oxygen and water vapor. The amount of vapor in the air can vary according to temperature and pressure. If the temperature and pressure change, the vapor can fall out or condense. You can see this phenomenon with your air compressor when you drain the water at the bottom of the tank.

The same is true for air-ride suspension systems. As the compressor pulls in outside air, the moisture can change from a vapor to a liquid. Most compressors will use an intake filter filled with desiccant that can absorb some water in the air before it enters the compressor.

Nitrogen is an inert gas that is less reactive to changes in temperature and humidity. It also can contain almost no moisture when it is inside a cylinder. Also, nitrogen molecules have more difficulty escaping through the microscopic spaces between a bladder’s rubber molecules. Nitrogen is a “slow” inactive gas labeled as inert. Oxygen, on the other hand, is a “fast” active gas that reacts with many materials and causes oxidation. Nitrogen is a dry gas that doesn’t support moisture.

Yes and no. Less sophisticated open-loop systems will run the compressor to increase pressure to the air bladders. The intake for these compressors typically has a filter that can trap debris and contains a large volume of desiccants. These compressors can be found on GM vehicles with the AutoRide suspension package or the Ford Explorer with rear air ride.

More sophisticated systems use a reservoir that the compressor replenishes when needed. These are called closed-loop systems. These systems can efficiently manage the air in the bladders and reservoir. They can keep a large volume of air uncontaminated in reservoir and bladders.

The system’s air mass is diluted when the compressor replenishes the reservoir. But, the air in the bladders on most of them will be exhausted into the reservoir and out the exhaust on the compressor or valve block. This can help keep more nitrogen in the system.

Closed-loop systems are found on four corner systems from Tesla, Land Rover and Mercedes. The service information advises filling the system with nitrogen to set pressure.

If the air ride system leaks, the compressor will try to compensate by running more. This can further dilute the clean air in the system. This also can allow moisture that forms water droplets. This cumulative effect adds more and more moisture to the volume of air in the reservoir and air springs.

The moisture can freeze inside the lines and valve block in colder climates. The humidity also can carry debris inside the system that can damage components. Also, since the system is compromised, the compressor must work harder to keep the pressure in the reservoir. In some cases, this can cause the compressor to overheat, and small plastic and metal particles can make their way into the system and cause even more damage.

It depends. Filling the system with one of these tools can save you from running the compressor for a long time to restore normal pressure. This can cause the compressor to overheat, or the system will stop the compressor to prevent damage. Also, some systems will not run the compressor until the vehicle is moving to mask the noise with the engine and tire noise.

Are the tools available? Yes, there are a few kits out there that will allow you to connect a gas cylinder or shop air to refill the system for many different makes, so buying several OEM tools is not required. These tools resemble A/C testers that fill the system with nitrogen for leak detection.

Do you really need to do this? You might get away with just shop air to refill the system. However, some systems are more advanced and can tell the difference between shop air and nitrogen when comparing the ride height, reservoir pressure and compressor run times. These can result in codes for the compressor or valve block.