Caring for that older Mercedes-Benz

These cars will run forever!” That’s a statement I often hear about Mercedes-Benz vehicles. While that’s true, I would like to add a sentence modifier that I rarely hear: “… with proper maintenance and repairs.” Mercedes-Benz vehicles will run for many years and miles, but only with regular attention. Unfortunately, most Americans’ habits – once the vehicle warranty has expired – are to repair only what is necessary, and only when it breaks, eventually selling or junking the car when breakdowns become too frequent or expensive.
One of my fellow Western Michigan Section members is a good guy and does the typical stuff, such as changing oil and coolant, regularly. However, a recent experience of his really got me to thinking. His wife and daughter had traveled about 20 miles from their home to a resort community one hot Saturday last summer. Upon returning to their ML320, a first-generation model with about 150,000 miles on it, they found that the vehicle would not start.
Much phoning and discussion finally led the women to have the ML towed to their authorized Mercedes dealer, approximately 50 miles away. Meanwhile, my fellow club member was left to retrieve his stranded wife and daughter because the car couldn’t be examined until Monday. It wasn’t long before the service manager called to report that the ML started fine and that no fault could be identified.
The ML’s owner immediately called me and asked, “What do you think?” If it did it once, it would do it again, I told him, and suggested that he drop the car off at my place that evening so my ace tech, Art Vaandering, could have a look at it the next day. He arrived first, with his wife following shortly thereafter in the ML. She left it in the driveway with the motor running while we discussed what the problem might be.
Then the ML shut down on its own. “That’s fine,” I said. “We’ll leave it there for Art to find in the morning.”
Naturally, the ML started right up the next morning. Once again, no obvious fault could be found. But Art is thorough. “I need to get this engine up to operating temperature to really see what is going on,” he said. He left for a 20-mile drive and was almost back when the car quit on him.
Coasting over to the side of the road, Art was glad that at least the problem had showed itself again. Given the age and model of the car, he had an idea what might be wrong. A half-filled bottle of water on the ML’s floor was just the tool Art needed to confirm his suspicions. When the water was poured on the crankshaft positioning sensor under the hood, the vehicle immediately restarted. Art replaced the faulty sensor – all that was needed to get the vehicle back on the road.
We’ve since researched this problem and confirmed what Art knew from experience with first-generation MLs and other models with similar engines. The crank position sensor is a necessary element in timing the fuel-injection system, but with age becomes susceptible to heat. At about 100,000 miles, the sensor starts behaving unreliably. It will work properly when cold, but after the engine reaches operating temperature, the heat in the engine compartment can cause it to fail temporarily, shutting down the engine. By cooling the CPS down with water, Art got it to run again. Most experienced Mercedes-Benz technicians now generally advise customers to replace the crank position sensor at about 100,000 miles.
The problem the dealer’s technician had was that he wasn’t familiar with the car and couldn’t re-create the circumstances under which the car failed. In addition, when the sensor stops operating correctly,  the diagnostic system may not record a failure code.
I try to learn something from every experience, but I thought that the message was more than obvious this time. Because I have a 2000 E320 station wagon (The Hammer Hauler) with nearly the same mileage and the same engine, the message was abundantly clear to me. And because I travel far and wide quite frequently with the HH, I had no desire to be stranded anywhere.
I told Art I wanted to be pro-active and replace the crankshaft positioning sensor in my car. “And while you’re at it,” I said, “would you give the wagon a good look over and see if you can find anything else that should be replaced?” Art reported that everything seemed to be in excellent shape except the idler pulley and the idler tension pulley for the serpentine belt – he didn’t like the sound. When spinning the idlers in his hand, there was a definite flat spot in each rotation.
He replaced both pulleys at the same time he replaced the sensor. While no car runs forever, I can expectantly look forward to many more trouble-free miles with normal maintenance.
My advice to you is the same. Be pro-active about maintenance and repairs for your car. Continue to take the car to a knowledgeable technician on a regular basis. Follow the factory’s maintenance schedule and encourage the technician to be on the lookout for items that might cause trouble. There’s still a lot of winter left, so if your car hasn’t been in to see its technician this year, now would be a good time to schedule a visit.