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Are Mercedes Diesels on Their Way Back?Posted 9/11/2007By Craig Van Batenburg, AAM
I interviewed Roger Young, a 23-year veteran of Wagner Motors, a Mercedes dealership in Central Massachusetts. He was very helpful and made it clear that the aftermarket only needs good training, tools and information to work on what he finds enjoyable work. Many independent techs will not work on European cars. When I travel (and that is a lot), I meet with techs from around the world. What I hear consistently among American independent techs is that they favor domestic brands; many quite simply do not like "those foreign cars." Dealerships love to hear that because it keeps their customers coming back, a free pass provided by independent shops. Why the reluctance? By accessing readily available service information and keeping up with the scan tools needed, most service issues with this popular German-branded car are not a problem. How good are these cars? I have received mixed reviews. Some knowledgeable techs tell me the quality has gone down from 1999 to present day. Others say it is a good product and always has been. My own experience is more in keeping with the former view. I will try, as always, to keep my personal views in perspective. Just in case we need a primer, let's look at diesels in general. Diesel engines look the same and share most internal components with gas engines, but they are simpler in design. The fundamental difference is that a gas engine runs much lower compression and therefore relies on a spark from the ignition system to ignite the fuel-air mixture. Because a diesel engine generates compression up to two to three times greater, it creates so much internal heat that the fuel will spontaneously ignite without a spark. One might ask, "If they are so simple, why do diesels cost so much more?" The theory might be fine, but there is always a bottom line. In reality, a diesel engine, like a high-compression gas engine, generates extra stresses that dictate substantially upgraded parts, including the engine block in some cases. The forces on pistons, piston rings, connecting rods, bearings and crankshaft rise in direct proportion with the two to threefold increase in compression. The injectors, injection pump and glow plugs, where fitted, are all high-precision, long-life and therefore expensive parts. A diesel engine requires a stronger starter motor to turn it over, which in turn dictates a bigger battery and alternator. Heavy-duty cooling systems are required to keep a diesel operating within its optimum operating band in all conditions. All of this generates extra weight. Along with the extra noise and vibration inherent in a diesel, most diesel installations require extra sound absorption measures, more complex and beefier engine mounts and stronger suspension. The extra torque (or twisting power) inherent in a diesel can also dictate extra body reinforcement, stronger transmissions, axles, clutches and other driveline components. When most of these parts are beefed-up in a commercial or heavy-duty 4WD vehicle, the impact of a diesel engine is not as pronounced. Is diesel fuel green? It is and it isn't. There was a push toward diesels years ago for environmental reasons but most of these are all but eliminated in modern gas engines. In Europe, a more insidious byproduct of diesel engines has since reared its ugly head as they have become more popular. Diesel exhaust contains fine particles, which can aggravate asthma and cause lung damage as well as premature death. The 2006 push to clean up diesel fuel and thus open the door for the latest clean-running diesels is timely when American diesel numbers are likely to approach levels where particulate emissions could become a problem. Most used diesel passenger cars in the states are of the old school and don't reflect the latest technology as fuel sulfur levels were not compatible with the latest designs. Diesel engines can run on a number of bio-fuels and this may prove to be an advantage in the future. With more people considering a diesel for their next car or truck, make sure you tell your customers to never, ever fill the tank with gas!
The "D" at the end of the model identification has been dropped in the United States. Mercedes-Benz will start selling the E320 Bluetec luxury sedan Oct. 15 in the United States. The start date coincides with a new, low-sulfur diesel fuel going on sale across the country. The E Class was recently redesigned, and the E320 Bluetec produces 210 hp and an astounding 400 lb./feet of torque from a 3.0-liter V-6. Mercedes says the engine will get a combined 35 mpg. Emissions will meet current U.S. requirements in 45 states. Not included are the green states of California, New York, Maine, Massachusetts and Vermont. The company expects new diesel models in 2008 to meet all 50 states' emission standards. The Bluetec clean diesel technology in the E320 Bluetec sedan, the winner of the 2007 World Green Car award, significantly reduces the soot and pollutants often associated with diesel engines via specialized filters and catalytic converters. Developed by Mercedes-Benz to be the cleanest diesel in the world, Bluetec is an emissions control system that reduces nitrogen oxide levels, the only exhaust components from diesel engines, which still exceed the levels in gas units. Bluetec technology reduces carbon monoxide, hydrocarbons, soot and especially nitrogen oxides through optimized combustion, filters, catalytic converters and treatment. Mercedes-Benz has developed Bluetec in two versions. The version used in the E-Class has an oxidation-type catalytic converter and particulate filter combined with a NOx trap system and additional SCR (selective catalytic reduction) catalytic converter. A second version (currently used in trucks in Europe) releases AdBlue, a non-toxic aqueous solution, into the exhaust stream, causing the production of ammonia. The ammonia serves to convert up to 80 percent of the nitrogen oxides into the harmless natural products of nitrogen and water. This is not a part of the new Bluetec coming here this year. What do we know about the 1999 Mercedes Benz E300? Some of the problems associated with the 1999 Mercedes-Benz E300D 3.0L, according to Identifix, is fuel leaking on injection lines at injection pump. An Identifix representative said, "The original seals used in the injection systems of these cars were not compatible with biodiesel fuels. If your customer is not prepared to replace the injection pump, injectors and fuel lines on the vehicle, they should not put biodiesel in the fuel tank." Be careful with those customers who want to use French fry oil! Common problems are the rear window regulators, air flow meter (AFM) and glow plugs. If one glow plug is bad, replace them all as they are hard to get to and troublesome. If the malfunction indicator light (MIL) is on with trouble P0380, it is glow-plug related. According to Identifix, check continuity on each glow plug. Perform an amp draw test. Each glow plug should be within 1-2 amps of each of the others. Glow plugs usually draw 12-15 amps initially, and after a few seconds, current flow will decrease to approximately eight amps. This can be done right at the connector on the glow control module. Using a generic scan tool will not give codes for the glow controller or individual glow plugs. If no glow plug faults are found, the control relay for the glow plugs is likely defective. You need a Mercedes-Benz compatible scanner to perform the activation test, which would indicate individual glow plug faults without having to go through manual testing. Some valve train wear was reported if conventional oils were used and a class action suit resulted. As mentioned earlier, special oil is required. If the maintenance reminder lamp will not reset, make sure all of the doors are closed. These are simple things to be aware of, and the Internet is the place to go for help. This is what a customer had to say about his 1999 Mercedes-Benz E300 Turbodiesel: "It is the best luxury car I have ever driven. It handles like it is on rails, it is quiet - which is phenomenal for a diesel - and has excellent power and amazing gas mileage - around 500 miles on one tank!" How do these two diesels stack up? From a repair standpoint, only time will tell, as the new Bluetec is not even here yet. One thing is sure: diesels are coming, and just like hybrids, you will need to service and repair them. I am studying diesels as part of ACDC's curriculum. It will be one way of weaning ourselves off of gasoline. Can Mercedes do a better job? With quality slipping, I think they have to. Ask an independent technician today what car he would recommend to a friend, and Mercedes is not on the list. Should you be in the German auto repair business? Yes, as the owners will pay you for a job well done. Once the learning curve is over (and diesels are coming back) there will be enough cars to keep you busy.
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Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
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Diesels are making a comeback! Many will be shipped to the United States over the next four years. Why? Global warming and the price of gasoline make a good business case once again. Mercedes-Benz has fallen in the wake of a quality machine; Lexus has led in sales for some time now. But the Germans are a well-educated and thoughtful bunch. We will compare, as best we can, the 1999 Mercedes-Benz E300D 3.0L to a new E320 Bluetec luxury sedan.
Because a diesel's high compression and precision fuel pump and injectors are fundamental to a smooth and clean running engine, they are more important than in a gas engine. Both are expensive to rectify so a good oil and filter change interval is more important than for a gas engine. The high compression will also quickly find any weaknesses in the cooling system including head gaskets, so coolant servicing is also more critical.
