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Greetings, everyone.

Require assistance with a problem with my A Class 2007 1.5 W169 (petrol) vehicle.

The serpentine belt became detached as I was driving. The power steering and ABS systems ceased functioning, but, I was able to safely return home without much distance remaining.

The technician installed a new belt, but it quickly became torn while the engine was running at idle speed. The first belt he substituted was drenched in grease and partly torn in the centre. The car had been experiencing oil leakage. Upon driving away, I saw a leak on my driveway. Oil stains.

I have been informed that there is a possibility of a leak occurring on the tensioner, however, my technician has said that he did not see any oil leakage from that area. He stated his intention to replace the tensioner and idler pulley tomorrow. Will this prevent the belt from being destroyed again? Do you have any insights on the potential source of this oil leakage? The coolant and oil levels were both OK and the vehicle was functioning well until the belt suddenly broke.

Thank you.

It is possible that one of the pulleys has become immobile due to a lack of movement or lubrication.

It is possible that this might be the reason, and I find it surprising that a skilled technician would not have inspected all the pulleys, idler wheels, and tensioners for issues prior to installing a new belt. The crucial aspect of it is the word "competent"!

I agree with GoodBoyCar's suggestion; it would be advisable to seek out an other garage or repair.
Most likely, the idler pulley is deteriorating. Replace both the idler pulley and the tension pulley.
I had similar issue with my CLK few years ago.

However, it fails to provide an explanation for the oil. Presuming that it is really motor oil. Is there an issue with the front seal of the crankshaft?

The oil might potentially escape via the oil test port located in front of the engine. This outlet is equipped with a square rubber gasket positioned slightly above the belt tensioner.
Do these automobiles have problems with harmonic balancers, similar to prior Mercedes-Benz models?

Typically, if a belt tears apart shortly after being started, it indicates that the belt was not installed properly and was slightly misaligned with one of the pulleys. I have personal experience with this issue, however I prefer not to elaborate on the details. It is possible that a pulley has seized, but this would be evident during installation. Additionally, pulleys are not very sensitive to oil, so it would not break quickly. It would take a considerable amount of time and slippage before it eventually fails.

The substance in question is motor oil. The potential sources of the leakage might be the crankshaft front seal or the top valve cover, which may be caused by a deteriorated rubber gasket.

Are these the two pulleys that I require?