srb1197

I bought my 2008 GL450 about 1 year ago, and it has had problems ever since.

When you shift into reverse or drive from park, the car moves, like shifts down, but doesn't jerk aggressively. Its almost as if its squatting in the back.

The second problem I'm having is that when stopped in drive, and then you let off the brake pedal, the car jerks back and forth as if its stopping sporadically. It shakes the whole car forward and backward, and its very uncomfortable. Once you give the slightest throttle, the shaking stops, even though the car hasn't sped up at all. I haven't touched the transmission fluid or even checked it so that maybe an issue.

Other than that, the ESP light is on, and the car is throwing a "Check component n49 steering angle sensor" code. All the signs lead to a bad steering angle sensor, but when I read the live data for the sensor, the data values are perfect. They stay 0 when the steering wheel is straight and they change appropriately corresponding to the angle of the steering wheel. So as far as I know, the actual sensor is working perfectly, but no matter how many times I reset the code, the ESP light comes back on every time I start the car. I really don't want to replace the sensor if its working properly, and I know if I take it to a shop they will automatically tell me to replace the part completely just to get me to pay hundreds in labor. Is there something im missing? Is there a fuse somewhere that I can check? Is there a relay? Anything I can do besides replacing it?

The power steering pump groans even though it has new genuine Mercedes fluid. The feel of the steering is very smooth when cold, but when the car heats up the steering wheel shakes when turning as if there is air in the system, even though I have bled the system several times. Did I do it improperly?

The car has regular full synthetic motor oil changes (LiquiMoly) and it got new brakes a few months into ownership, but the jerking problem persisted before and after the new brakes. Please let me know if you have a solution or a place to start on any of these issues. Thank you!

eric_in_sd

Hoo boy.

Do basic diagnosis and service, some of which you have already done.

I am no transmission expert, but I would say the first step there is to drop the pan, check for metal in the fluid, and if it appears clean, change the filter and replenish with the recommended amount of fluid. It vaguely sounds like it is low on fluid and the torque converter needs to spin and fill up, or something like that. But you would have to wonder how it got low on fluid in the first place. Brace yourself for some expensive transmission repairs or replacement, though. Properly maintained, the 722.9 transmissions last quite a long time, in the 150k and up range, but abused will fail well below that.

The SAS is tricky. It is an optical system; I was able to rejuvenate mine simply by careful cleaning with isopropyl alcohol 50%. If you are careful and methodical it really is not hard to do. I do not know what to say about your tests that seem to indicate it functions properly; all I can suggest is that the self diagnostic systems are not perfect. Troubleshooting with a diagnostic computer is a little like calling up a party to get directions, only to get a drunk girl on the phone.

Off the top of my head, you need a power steering pump. I doubt the bleeding process was at fault; in my experience the system is pretty good at getting air out of the rack and into the reservoir. Why the pump failed, I could not guess. But failing as the fluid warms up sure sounds like a pump failure to me.

In the future, seeking advice, state the mileage on the vehicle and the mileage on affected parts - and the last services done on those parts.

Have fun. It can be an aggravating vehicle, but it sure is solid when everything is properly cared for.

Max Blast

ESP errors and weird steering can be related and not necessarily a bad pump. The x174 has speed variable steering, and a failing SAS or wheel speed sensor will put it in highway mode, which will feel very heavy at rest, or intermittently so.

the SAS code might be hiding a wheel speed sensor failing, which will lead to all the symptoms you’ve described here - jerky steering, grabby brakes that may feel like poor drive engagement, ESP light etc…Does the SAS code come back every time you clear it? Then it is the sensor, despite what the live read out is telling you.

If your issues aren’t attributable to the above the shuddering and lurching in drive you are describing can also be the transfer case chain slipping, so check that before serving the trans. If it isn’t that, it sounds like the torque converter is shuddering. Have the trans serviced with the proper fluid and check if it repeats.

you may have two separate issues here, a bad SAS that is masking as other drive ability issues so deal with the ESP light first then throw money and attention at the drivetrain.

srb1197

Thanks for detailed responses you both. Really appreciate it. Car has 145k miles, original transmission and engine. I have no idea the miles on the specific parts cause I only bought the car a year ago. I’ll definitely check the trans fluid. I think I’ll just bite the bullet and replace the sensor. Not sure why it’s giving correct readings but sometimes just replacing the part is better than ripping your hair out trying to find why lol. I’m only 15 so I don’t really have the time to worry about the car like I am right now. I do all service myself on top of school and sports so I hate that these issues are taking up my time so thanks for next step!

eric_in_sd

The SAS is not a cheap part. $150 if I recall correctly. Frankly, the hard part is the disassembly of the steering column. Cleaning versus replacement is a balance between cash and time.

Change the transmission fluid as suggested. This is not a simple procedure, so ensure you have help if you are not completely confident. Take it to the dealership if you have neither the skill nor the help. Do not take it to any second tier shop for this.

FCP Euro will ship you a kit including the bolts, the gasket, the filter, and the fluid - but the fluid level is tricky to get right, requiring a diagnostic computer to see the fluid temperature.

While there is nothing known wrong about substituting Liqui Moly oil for Mobil 1 0W-40, why risk it? Engines depend on the oil being the right viscosity at the right temperature. Use the Hengst OEM filters, or possibly substitute Fram Ultra, which apparently is a deeper filtering media than others. Properly cared for, the motor will last essentially forever.

srb1197

If I use the AMSOIL easy packs, I dont need a transmission fluid pump to service the trans right? FCP euro is saying I need a 160 dollar pump which is ridiculous. If I use those squeeze pouches I think ill be fine. Theres no drawback to using those right?

eric_in_sd

Do you have compressed air? If so, build this out of a soda bottle and some vinyl tubing:


You can also get fluid pumps for a lot less than $150. Or the squeeze packs, with which I am not familiar, but can imagine. Just make sure the transmission fluid is the right stuff. People around here get super fussy about only-the-best-for-my-baby, which can get a bit silly: I bought Pentosin power steering fluid at $16 a quart, only to get home and see the owner's manual specifies Dexron III. ATF. Which is like a buck a quart. But given how costly the transmission is, I would make sure to use the super legit item. The same goes for motor oil, by the way. Yeah it's guaranteed compatible, but how are you going to cash in on that guarantee if it's not?