I just finished the Coil conversion from Airmatic on my 2007 E550. It rides great and I have no problems with the suspension, but my steering is stiff and when I am stopped and I turn the wheels over halfway in each direction I hear a groaning sound like it's low on fluid. The fluid level is fine and I didn't touch anything related to the pump during the conversion.

The only thing that I did that may contribute to the issue is lowering the front before finishing the rear coils. I had the car up on four jack stands. I finished the front first, put the tires back on and lowered it to the ground with the back still elevated on jack stands. Due to a series of unfortunate events, it took me 5 days to get the rear finished and on the ground.

Could this elevation from rear to front for 6 days have caused this?

Is there anything you guys can think of that may have caused this? BTW, I have tried to get the air out with wheels off the ground and turning side-to-side 30 times and also parking on an incline. It has helped but the steering is still stiff and I still have some noises.

 

Start by spraying wd40 or rubber compatible spray on upper control joints and lower control arm rubbers.

 

I sprayed silicone spray on the control arm bushings, not much of a difference yet but I will let it set in for awhile.

Also. When I raise the front and get both wheels off the ground, I can spin the wheel with one finger and the only time it makes any noise is when it bounces off the stops (left and right). It makes a whining noise when it hits the stops. When the wheels are on the ground and the car is stationary it is very difficult to turn the wheel. Once in motion, even at 10 mph, it is much easier to turn the wheel, but slightly stiffer when making turns.

 

Check the pressure solonoid on the steering rack could of got damaged or disconnected during conversion

 

How does steering behave when revs are up? It would be worth checking speed sensors on tyres.

 

The car steers fine at higher speeds, but when slowing to make 90 degree turns it stiffens.

I will check the steering solenoid when I get home this afternoon. I see that I can do an actuation test in Star to turn the valve on, I will do that first. Is there anything else I need to do with Star as far as disabling the Airmatic, etc.?

 

have the same exact problem but non airmatic car.

 

 

I ran Star diagnostics and I have a fault code 4FE7 in the Adaptive Brake Control Unit that I missed before. It means "Check component Y10 (SPS Solenoid Valve)". I ran the test that was available to see if the SPS Solenoid was working. The steering was supposed to be easy if I clicked F3, and stiff if I clicked F4. The steering was the same on both F3 and F4.

I am going to double check all wiring and make sure all is okay. If it is okay, does that mean it is the SPS Solenoid or could it be a wheel speed sensor or ??????.

 

PROBLEM SOLVED !
I traced the wire from the SPS Solenoid and found a break at the connector. It was too close to the connector to splice in, so I cut out the connectors and spliced the wires back together and now I am up and running. Thanks to all that helped me pinpoint the issue.