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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53985
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Ml32o: Just got back from MB dealer with following notes on

Customer Question

Just got back from MB dealer with following notes on sensor codes from my 2003 ML320:
No back pressure from exhust on L-bank and very little from R-bank. RemoveCYL. heads to clean. Also timing chain stretched.
Quoted $6k plus....make sense?
Submitted: 2 years ago.
Category: Mercedes
Expert:  Marty replied 2 years ago.
Hi, welcome to Just Answer. My name is***** you post the fault codes?
Customer: replied 2 years ago.
Only code I recall is 4100...the dealer invoice said they cleared the secondary air injection code and the stretched chain code.
Expert:  Marty replied 2 years ago.
Ok, it is somewhat common for the secondary air injection passages in the cylinder head to plug up and cause the P0410 code. There are other possibilities for the code as well. There are tests that they should have performed to determine that the passages are plugged. If they have checked the air pump and the air injection valves and determined that they are working correctly the passages may very well be plugged but before spending $6000 to clean the heads I would get a second diagnosis from a reputable independent Mercedes specialist. The stretched timing chain is very unlikely. It sounds like they are selling you a chain simply because they will have the heads off. If the passages are indeed plugged they may be able to be cleaned on the car. The air injection valves are removed and a top engine cleaning solvent is poured into the passages and left to sit overnight. I've had success in cleaning the passages this way. This is also a good test to confirm that the passages are plugged. If the solvent flows right through the passages and out the exhaust it tells you that the passages are not plugged. A second diagnosis is a must in my opinion.
Let me know if you have any questions.
Expert:  Marty replied 2 years ago.
Hi, I'm just following up with you on the Mercedes. Was my answer helpful?