MERCEDES' 10 GREATEST ENGINEERING BLUNDERS
Over the next 10 weeks, we will discuss on a weekly basis some of the greatest mistakes made by Mercedes on operating and mechanical systems. These blunders are subjective and a matter of interpretation. I know there are those of you who may disagree and certainly have your own list. I would certainly welcome your input when you disagree with me.
The first blunder on the list, most readers will agree with, but those following are subject to interpretation. The word Mercedes in synonymous with design engineering, innovation, and perfection, so how could blunders ever be associated with this marque? Post WWII Mercedes had in its employ some of the greatest minds and engineers of the time: scientists and engineers who were responsible for WWII weapons such as the Tiger Tank, the ME262, the V-2 rocket, and other advanced weapons of design and destruction. After the war, many of these geniuses were to be employed by Mercedes when their production started again in 1947.
One of the first strategies used by Mercedes was to design an automobile which would make the Mercedes racing team competitive. Not only was Mercedes competitive, it dominated in Gran Prix racing in the 1950's. With this foundation, Mercedes was to epitomize automotive engineering for decades to come. With this background, it is a true mystery to determine the genesis of these forthcoming mistakes.
#1. THE INFAMOUS MERCEDES BENZ WIRING HARNESS
The defective harnesses were limited to certain years (1992 - 1996), and certain models. The 1992 and 1993 190E were not affected, nor was the 1992 300E. The models most prone to these defective harnesses were the 124 chassis 1993 - 1995, the R129 (300 SL, 500/600 SL, SL 320, S4 500 from 1992 through 1995. The W140 chassis (300 SE, 400 SE. And 400 SEL, 500 SEL and 600 SEL from 1992 through 1995). The W202 chassis (C 220 and C 280, 1994 and 1995) was also affected.
The decision by MB to use an eco-friendly coating for their wiring is relatively mind boggling. So are we to presume that MB made the wiring so that it would degrade when the cars were in landfills? Cars do not go to landfills. They are recycled. These coatings insulate copper, which, at this writing, is about $3/lb. Every MB manufactured 1992 - 1995 had engine and transmission wiring harnesses that would go bad - not 75% or 90% of the time, but 100%. Period. Mercedes knew about this issue within the first 2 years, but did not do the right thing and recall these cars and replace the harnesses? Of course not.
This problem occurred throughout the entire MB lineup: C, E, S, and SL classes. If you have a Mercedes of the 1992 - 1995 years with an original MB harness on your car, it is bad. Not only is the engine and transmission harness bad, but also the length of wiring to the throttle actuator, which means this very expensive part is defective - not maybe, but the chance of these harnesses being bad are 100%. So we have a 94E Class that from original needs a wiring harness, a transmission harness, and a throttle actuator. What happens inside these harnesses is that the insulation deteriorates, the wires touch each other and may damage the throttle actuator control unit and also the ECM. I'm sure the Mercedes bean counters conferenced with the engineers and decided that to financially recall all of the MB's made from 1993 - 1995 would be devastating to the bottom line.
If you are buying one of these fore-mentioned vehicles, you must have these harnesses inspected. The engine harness can be inspected easily by opening the hood, but the transmission or alternator harness is inspected by putting the vehicle on a lift. The other harness to be inspected is the harness for the electronic throttle actuator. To inspect this harness, a small slit with a box knife will expose the wiring. If you have a throttle actuator of the 92 - 95 years, the degraded insulation will expose copper wires. When this happens, the exposed wires will touch and possibly short the control unit for the throttle actuator. This control unit is called an E-Gas unit. We still see models of this vintage that have the original wiring harnesses, so if you are considering the purchase of one of these cars, make sure you have it inspected. New engine harnesses run from $800 - $1600, transmission harnesses are $250 to $550, and throttle actuators must be rebuilt because new ones are so expensive. Once again, if you are considering purchasing one of these cars, please pay a qualified technician to inspect these components.
2.) The Mercedes Single Row Timing Chain Mystery
Truly, I know there is an individual who knows why this single row timing chain was installed on all Mercedes V-8 engines which came to this country from 1981 - 1983. The cars we are talking about are not its lower end models, but the 380SL, 380SEL, 380SEC, and 500SEL.
In 1981, the model line-up for MB of North America included the 240D (4 cylinder), the 300D (5 cylinder), 300SD (5 cylinder turbo charged), the 280E, CE (6 cylinder gas), and of course the 380SL, SEL, SEC (all 8 cylinder gas). All of these models had double row timing chains with the exception of the 3.8 liter V-8's which had the single row chains. This engine was the 116960 for the U.S. market, while the European and other markets had 3.8 liter engines with double row chains!!!
So why? The double row chains would require additional parts such as: double row cam gears, double row idler gear, and a double row gear on the crankshaft. At the time of assembly (of the engine), the addition of a double row chain and its auxiliary components may have added $25 to the total cost. I can just imagine a Mercedes of Germany internal memo between the engineering, marketing, administrative, and finance departments that may go like this: "We need to **##!! the Americans, they are making too many demands - air conditioning, power windows, etc., and soon they may even want cup holders - so let's put in a single row chain in the most expensive sedans and coupes which will probably last through the warranty period, and we can make big bucks when the chains fail! Also, in a few years, Herr Dieter has plans to make inferior wiring harnesses, which we have also designed to fail once the warranty period has expired. We will take our revenge on the Americans for helping the British and the French!"
The previous, of course, is a ridiculous statement, but it makes almost as much sense as putting a single row chain in these fore-mentioned cars. I truly don't believe this was an engineering decision, because Mercedes has always over-engineered. Is this a bean counter issue? Risk and return I don't believe, there is not enough return to make such a decision. I don't think this is a marketing decision as less is not more. So this leaves us with something else; I would surely welcome others' input.