TSB's

Grinding/gushing Benz

If the owner of a 2006-2009 Mercedes-Benz complains of a grinding or gushing noise that sounds as though it’s coming from the steering system/power steering pump, one of the possible causes may be the A/C compressor belt drive. Models include 163, 164, 171, 203, 209, 211, 215, 216, 219, 220, 221, 230 and 251.

The noise is similar to the noise produced by the power steering pump when ingesting air. This type of noise is present at both idle and higher engine speeds, and can be heard whether the steering wheel is stationary or moving and the noise frequency increases with engine speed. The noise intensity increases toward the steering wheel end limit stops.

The noise does not change by switching rhe A/C compressor on and off. Evacuating the refrigerant will not change the noise, since the A/C compressor belt pulley runs continuously with the engine.

Do not replace the A/C compressor belt pulley merely on suspicion. To determine whether the noise is caused by the A/C compressor, perform the following test using a shorter poly-V belt. It is absolutely essential to follow the sequence in the following procedure.

1. Detach the original poly-V belt.

2. Install poly-V belt P/N A011 997 96 92 on vehicles with M112/M113 engines or install poly-V belt P/N A011 997 04 92 on vehicles with M272/M273 engines. With the shorter belt installed, the A/C compressor is not driven by the belt. The A/C compressor pulley is bypassed. Route the rest of the belt the same way as the original belt.

3. Start the engine and listen for the complaint noise.

4. If the complaint noise is no longer present, replace the A/C compressor belt pulley. Refer to the latest version of DTB P-83.55/87 for A/C compressor poly-V belt pulley replacement.

5. If the complaint noise is still present, it is not due to the A/C compressor. Resolve the noise issue by following the procedure in Star TekInfo > EDAC > Diagnostic Guides > Power Steering Diagnostic Guide (latest version) > Start > Noises in steering system.

When testing for a faulty A/C compressor pulley, install a shorter belt that bypasses the A/C compressor pulley. “1” in this illustration depicts the A/C compressor pulley.
<p>When testing for a faulty A/C compressor pulley, install a shorter belt that bypasses the A/C compressor pulley. “1” in this illustration depicts the A/C compressor pulley.</p>

 

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