Most of you know that I’m not really doing much mechanic work now but I still like to keep a finger in (fnarrr) and do bits and pieces. I’ll try to post more stuff like this when I’m doing car work but it won’t be a regular feature.
This is the easy way to find a leak in an air suspension system without getting your hands dirty.
The first thing you need is some diagnostic software and a bit of basic knowledge how to use it outside of just scanning and clearing DTCs. This method should be possible with all modern diagnostic software excluding cheap code readers etc.
You need to enter the suspension system, read the codes and make a note of them then clear them. Clearing them can temporarily enable a disabled system allowing you to carry out tests if you work fast.
The codes I got were,
01583-Leak detected in system
01577-Switch off due to excessive temperature
01583 is pretty self explanatory, it means the system has detected that the air pressure is dropping somewhere, ie an air leak.
01577 is a symptom of the air leak. It’s important to remember that not every fault code is the main fault, it can be caused by something else which is where a lot of people go wrong. Because of the air leak, the compressor is running for an extended period of time, causing it to overheat and switch off. This could be misinterpreted as a faulty compressor or relay but we will carry out the full diagnostic process rather than fire the parts cannon. FIFT- Fix It First Time
Now we’re going to find out where the leak is.
Enter the live data function and select compressor relay status and absolute height of all 4 shock absorbers. I have only selected the front shock absorbers because I already know the fault is in the front and am showing for demonstration purposes.
Now, select graph mode and overlay all parameters in one sheet.
It should look like this,
You can see from the legend that the dark blue line is compressor on/off status, purple is left front height and light blue is right front height. Unless you are sure the problem is in the front, you should also have selected height for both rear shock absorbers and will have 2 extra lines.
Notice how when the compressor is in the on state, both shock absorbers raise but the front right never reaches the same level as the left. When the compressor switches off, both shock absorbers start to drop. The front left drops slightly and levels off. The front right drops massively and continues to drop until it reaches the lower limit. The compressor switches on again just before 120s and the cycle begins again.
We can see from this that the problem lies in the front right corner so 75% of the manual diagnostic work has been eliminated. I already know the problem is a leaking airbag because the one on the other side has already been replaced, but you will want to get a spray bottle filled with soapy water and start spraying it all around the air suspension components on the front right corner when the system is running. Wherever you see bubbles, that’s where you have an air leak. This is easier to do if you have a 4 post lift where you can raise the car but still have the wheels grounded. I’m lying on the ground on a piece of carpet which makes it more difficult to access and see components.
A couple of final warnings.
Never jack up a car with air suspension without first putting it in jacking mode. This can play havoc with the calibration settings and cause you problems when set the car back down.
Never open any part of the suspension system without first venting the system. Your computer should have a function to do this somewhere in actuations or special functions. The danger of something pressurized flying off and hitting you is real. Slackening a pipe to let the pressure out of the system isn’t a good thing to do. When you loosen a nut on a pipe, you have less threads holding it in place. The pressure can easily overcome the lesser amount of threads, strip them and blow the fitting off. If it doesn’t hit you between the eyes, you’re left with 2 damaged threads which will be difficult to repair. Even if it does hit you between the eyes, you still have to repair the damaged threads you caused after you go to the hospital to get stitches.
One last thing before anyone says it, I know you can use your eyes to find the problem. This is just an exercise in some of the things you can do with your computer.