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Hi everyone. A few weeks back I was driving when the car went into limp mode. It lost power and the car felt like it lost the turbo. When I plugged in a OBD scan tool I got code P029921 "The Turbo 1 boost pressure is too low. The signal amplitude is below the minimum amplitude". I might have thought it was the turbo solenoid valve so I got a new one from Mercedes but still the same issue. I believe it's either the waste gate stuck/not working properly or it might even be something with the turbo. Seeing my options, i'll have the replace the turbo completely as the waste gate isn't a part I can just buy and replace.
Any help on where I can get a replacement turbo/if you know anyone selling a working turbo would be awesome. A new one from mercedes is about $5000.
Update: i put vacuum to the turbo actuator TS Vacuum Cell and it did not go past -5 Vac. However, when i put my index finger over the nipple where the actuator is, and push the rod my self it does hold vacuum. i'm unsure if it's supposed to do that or not though. I plan on purchasing the vacuum actuator from mercedes as it's only about $100 and it's worth a try to swap out.
Also to mention, I did find some oil in the turbo but very minimal. I believe this was there before as well but it's probably common since the intercool is connected to the turbo? Any thoughts on that?
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by Billyismyname
Update: i put vacuum to the turbo actuator TS Vacuum Cell and it did not go past -5 Vac. However, when i put my index finger over the nipple where the actuator is, and push the rod my self it does hold vacuum. i'm unsure if it's supposed to do that or not though. I plan on purchasing the vacuum actuator from mercedes as it's only about $100 and it's worth a try to swap out.
Also to mention, I did find some oil in the turbo but very minimal. I believe this was there before as well but it's probably common since the intercool is connected to the turbo? Any thoughts on that?
Wow! New England climate takes its toll on cars! What year, model, and engine are you talking about? Did the new actuator fix things?
From other threads, it appears that Mercedes uses the open position for the wastegate as the default. That's good because any malfunction keeps the wastegate open and the worse is loss of boost and maybe limp mode. A default closed position can cause overboost and serious engine damage, like a blown engine. Also, Mercedes seems to use a separate vacuum pump for the actuator versus engine vacuum. If you are still having problems, I would check that the vacuum pump and all vacuum lines are in good working order since you confirmed that the actuator is OK. Using XENTRY you can actuate the switchover valve and vacuum pump.
Here's a list of all the test functions you can perform with XENTRY. Some of the tests are manual and some are automated. This is for my car with the M276 3L biturbo. It may be different for yours.
Last edited by JettaRed; Oct 11, 2024 at 09:16 AM.
My turbo was replaced and the cost on it was $1700 but because I have warranty on it, it cost me nothing. In my B-Class if you get a turbo problem it will tell you where the problem is. For example: if it's a problem with the waste gate it will tell you there is problem with the mechanical.
The replacement actuator did resolve my turbo issues. I had to take out the entire turbo and the exhaust manifold (they're one unit) and change it out that way because it's very crammed and very minimal space to remove the rear of the actuator.
While I had the turbo removed I did some "while i'm in there" work such as replacing the exhaust manifold gasket which looked like it was as thin as a piece of paper and on the brink of failing, changed out the exhaust manifold studs and bolts with new ones, bent the turbo wastegate door/flap more inwards so it has a more positive shut/seal, and replaced all the oil and coolant lines from and to the motor + the turbo. Also a lot of miscellaneous things like bolts, engine mounts, changed the waterpump (super easy without turbo in the way) and cleaned the inside of the catalytic converter.
Dealer wanted close to $11,000 for all that work (mostly because they wont replace the vacuum actuator, they replace the entire turbo). I bought all parts listed above for less than $750.
At the time of issue, my car had around 100,000 miles. Now I currently have 156,500 and it's still going strong after all that work. Next job is to replace my wrist pins and piston rings + camshaft bearings.
The replacement actuator did resolve my turbo issues. I had to take out the entire turbo and the exhaust manifold (they're one unit) and change it out that way because it's very crammed and very minimal space to remove the rear of the actuator.
While I had the turbo removed I did some "while i'm in there" work such as replacing the exhaust manifold gasket which looked like it was as thin as a piece of paper and on the brink of failing, changed out the exhaust manifold studs and bolts with new ones, bent the turbo wastegate door/flap more inwards so it has a more positive shut/seal, and replaced all the oil and coolant lines from and to the motor + the turbo. Also a lot of miscellaneous things like bolts, engine mounts, changed the waterpump (super easy without turbo in the way) and cleaned the inside of the catalytic converter.
Dealer wanted close to $11,000 for all that work (mostly because they wont replace the vacuum actuator, they replace the entire turbo). I bought all parts listed above for less than $750.
At the time of issue, my car had around 100,000 miles. Now I currently have 156,500 and it's still going strong after all that work. Next job is to replace my wrist pins and piston rings + camshaft bearings.
Man, what model is your car? I have a 2013 c240 and my actuator is stuck under the power steering reservoir. Did you have to take that out?
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