In this brief article, we are going to discuss the different BMW 5 Series Air Suspension problems, what the causes are, and their troubleshooting Tips.
What are the most common air suspension issues in a BMW 5 Series?
The most common BMW 5 Series suspension issues are:
- Rear-End Sagging
- Uneven Ride Height
- Tips on replacing Air Spring
- Tips on Rebuilding the Air Compressor
BMW 5 Series Suspension Set-up
The BMW 5 Series is categorized as an executive Luxury sedan that has been manufactured since 1972. The 5 series is currently on its seventh generation
In the 5 Series, since the 6th generation (F10/F11/F07/F18 from 2010 to 2017) the Front suspension set-up has been a Double Wishbone with a Coilover Strut. There are 2 separate Lower Control Arms and therefore 2 Lower Ball-joints for the wheel Spindle with a Torsion bar & coil springs.
The Rear suspension of the 5 Series is a 3-link independent suspension (lower control arm, Upper control arm and a Toe control arm) with a Torsion bar & coil springs. The lower control arm was a 2-in-1 link with 2 bushing joints to the subframe and for this reason, the trailing arm was eliminated.
The 5 Series G30 model sedans would get coil springs as standard. Whereas, the G31 Touring models, regardless of the variant, all feature rear air suspension with automatic self-levelling as standard equipment.
In both the options, the standard coil spring would be replaced by an air strut and bottom mounting bracket to go with it as well as a different shock absorber that was tuned for air struts.
- Rear suspension loses ride height completely
- Driving in this condition feels like there is no suspension
- Explained as seen on the F11 6th Generation 5 series with rear self-levelling air suspension
- Rear air suspension sags due to loss in air pressure
- The air pressure loss could either be due to
- A failed compressor, or
- A leakage in the air suspension system
Troubleshooting Rear end Sagging
- Use a Diagnostic interface plugged into the OBD II to read the diagnostic trouble codes (DTC’s) that were stored at the time of the fault.
- The most usual DTC the appears for a sagging suspension is the one that says
“Raise Control Time”
- This DTC means that the systems detected that the compressor took too long to raise the suspension. The system understood this by reading the ride height sensor levels and observing that they did not change.
Check for Compressor Function
- Use the diagnostic tool Under EHC-> ‘Component Activations, “Activate” both the Rear Air springs
- First, listen to see whether the compressor turns on
- If the compressor does not turn on there is a high probability that the compressor fuse might be blown
- Check the compressor fuse (orange 40A fuse) within the fuse box located under the dashboard in the glove box and replace it
- Once again, using the Diagnostic tool, “Activate” the rear Air Springs. See whether you can hear the compressor working.
- See whether the suspension raises. If it does not, then it means that the air springs are not getting the required lifting pressure from the compressor.
- To find the reason, it would be useful to measure the pressure developed by the air compressor.
- In the F11 generation, the EHC system did not come with an air pressure sensor so that the diagnostics could read the compressor pressure.
But if you wish to check compressor air pressure, you can either:
- Use a manual gage and adapt it to the BMW air compressor’s air connector fitting
- Use an electronic pressure sensor from another device using an adaptor to the BMW compressor’s air connector fitting. Here you will need to use a pressure reading interface and software application to get the readings on a Laptop.
- The pressure must go beyond 22 bar. If not, it means that the compressor has failed.
- Although compressor replacement would be the best option, you could try rebuilding the compressor after reading this section.
- Replace the compressor in your suspension system
Air Spring Leakage Check
- If there is a loss of suspension height in spite of a properly working air compressor, then the air leakages could be the next thing to suspect.
- Air leakage related suspension sagging generally is seen when the car is parked overnight and sometimes even over a period of days.
- Air springs are known to wear out and crack at the rubber bellow surface gradually after accumulating mileage. They generally would last 70K to 80K miles depending on usage.
- In a high mileage vehicle, the air springs would be the first place to check for leakages.
- Using the Diagnostic tool, Activate the rear air springs. Then spray springs with soap solution to check for leaking.
- After spraying the soapy water solution, wait to see if there are white foam bubbles that stay at one spot even after wiping it with a finger.
- In cases where the leak is major, you even hear a hissing noise coming from the leakage point and be able to locate it by ear.
- Once you have confirmed that there indeed is a leak, the air spring has to be replaced. Read this section to know tips on how to easily replace your BMW 5 series air spring.
Uneven Ride Height
- One corner sits lower than the other at normal ride height
- Air suspension works fine; no issues with raising and lowering at all 4 corners
Troubleshooting Uneven Ride Height
- First, make sure the car is unloaded and parked on a surface with no slope.
- Now measure the vertical distance from tire top to the bottom of the fender on the sagging side as well as the non-sagging side
- One corner sitting slightly lower within 15mm of difference to the opposite side points to a ride height calibration issue.
- As long as the lower-looking corner is functioning and not fully sagging, you could eliminate the possibility of an air strut leakage
- To perform the calibration you need to plug in an OBD diagnostic tool
- In the diagnostic menu go to “air suspension”-> “Functional Tests” -> “Special Functions” -> “Air Suspension Calibration”
- Here you will be asked to enter the wheel rim size of your vehicle. Depending on this, it will tell you the recommended ride height for the front and rear wheels
- Next, you will be asked to enter the measured height from the rim outer circumference closer to the ground up to the fender bottom edge
- Once you enter these values for each of the 4 wheels, the system calibrates the suspension and levels it for you
Tips on Replacing the Air Springs on a BMW 5 series
- Before replacing the air spring, you need to relieve the air pressure so that it can be compressed for removal. The air release can be easily done at the rear of the vehicle at the compressor end. The air inlet fitting of the air spring is not accessible by hand, hence this procedure.
- Before removing the air spring for replacement, be sure to relieve the air pressure from it at the valve block, which is located in the underbody near the rear bumper.
- Relieve the left or right air spring valve by loosening the connector gradually. If this is done suddenly, then you could risk damaging the O-rings within the air connector fitting.
- While replacing the Air Spring, be sure to cut off the portion of the line that was squeezed or stretched in the old fitting after disconnecting. The reason being that the old used portion of the air line could crack and cause a potential leak.
- Reconnect the air inlet fitting to the newly cut end using only new fittings. These are one-time use only and must be replaced every time the air strut is removed.
- Some aftermarket brand replacement bellows tend to give a higher service life as compare to the original OE spare part
- Moreover, some aftermarket replacement parts also come with a lifetime warranty instead of a limited warranty offered by BMW
Tips on Rebuilding the BMW Air Suspension Compressor
- This applies to air suspension from all generations of BMW
- To check for compressor issues, you need to dismantle it and check the Piston, Cylinder and Piston ring condition. Ideally, the piston rings must have elasticity
- The best course of action would be to replace the compressor, but for economic reasons, you could also try using a repair kit (Piston and rings) to rebuild the compressor.
The rebuild option does come with risks as there could be issues in the compressor other than just the piston and rings.
- The compressor has an Air Dryer integrated in the same assembly. This Dryer is filled with Desiccant Granules
- When the desiccant granules have reached their moisture retention capacity, they expand and leave no room for the air to freely pass through, leading to a partial blockage.
- When new, the granules should be Blue in color. They gradually become brown over time. If they turn completely brown, it means that the granules have fully saturated.
- The desiccant granules are replaceable and can be easily done
In this brief article we have discussed the different BMW 5 Series Air Suspension problems, what the causes are, and Troubleshooting Tips.