Questions and Answers from mbca.org/techtalk

by Jonathan Hodgman

As an MBCA member, if you have technical questions regarding your Mercedes-Benz, you can get answers from Jonathan Hodgman and other club technical specialists on the Tech Talk Home page at mbca.org. In this new feature of The Star, we’ve asked Jonathan to give us some examples of the questions he’s answered during the past two months.
Better performance from a 1994 500E?
Q: I recently acquired a ‘94 500E as my daily driver but am looking to improve brake performance while reducing brake dust if possible.  Secondarily, are there any ready performance upgrades available that won’t break the bank?
A: Wonderful choice – 500Es are a superb way to make the daily commute routine less so!  For brakes, you can readily upgrade to the R129/SL600 brakes front and rear.  This will give you a 334mm rotor up front and a 300mm rotor out back.  You’ll need the rotors, calipers and dust shields to make a proper conversion.
I recommend installing braided stainless-steel brake lines. Paragon Performance makes quality lines that are Teflon coated to prevent chafing. We have used them on our cars with excellent results.  For brake pads, I recommend running Akebono Ceramics or Porterfield R4S depending on your level of aggression. I’m partial to the latter for spirited driving. Couple that setup with some proper brake fluid – my favorite being Castol SRF – and you will have a very strong brake package that also would allow for some track/autocross duty, should you feel the desire.
For power, your best value would be to find an LH control module from a 1992, which comes equipped with wide open throttle (WOT) enrichment.  This has been proven to add 5-7 horsepower. Beyond that, some small gains can be had with a full high-flow cat-back exhaust system. However, there is nothing available off the shelf and this would be a custom build.
What’s wrong with my 2006 R350
Q: Our 2006 R350 will occasionally run unevenly and the Check-Engine light has come on. The car is currently out of warranty with just over 100,000 miles.  Any obvious answers as to what might cause this?  Our dealership is over an hour away and I was hoping to gain some insight before making the trip.
A: The engine in your R-Class (M272) is a DOHC V-6 equipped with balance shafts to mitigate the vibration inherent to a V-6.  Unfortunately, the early examples of this engine suffer from insufficient hardening on the gear that is responsible for turning the balance shaft. Mercedes-Benz is keenly aware of this situation.  What you might do is call your local dealer, inform them of the symptoms and make an appointment to stop in.  They can check rather quickly if this is indeed the problem.  If it is, the dealer might even take care of it for you.  If that is not the problem, you’ll at least have a diagnosis of what is causing your issue and can decide then how to proceed.
Better sound in my SL
Q: I have a delightful 1988 560SL with 69,000 miles. It is in very good shape. I am upgrading my stereo and suggestions for replacing the speakers as mine – only two small ones in the dash – are hardly working. Any info would be appreciated.
A: That said, a set of 3.5-inch Infinity Kappas will improve things significantly over stock and will be adequately driven by the stock head unit, even with the somewhat mismatched ohm rating between the two.
But to achieve decent sound in an R107, you will need additional speakers. If your car is not equipped with kinder seats, you can readily add speakers to the rear parcel shelf without ruining what would otherwise be a difficult part to replace should you want to return the car to stock at a later date.
Budget-wise, a pair of good-quality 6-inch by 9-inch loudspeakers will fill the cabin with  lots of sound, with the top up or down.  If you want to get into crisper/higher-end sound, then a two-way or three-way speaker system can also be fitted, but will require external amplification to be driven properly.  As for head units, Nakamichi makes a nice one that looks the part in 1970s–1990s Mercedes.  The unit has RCA phono jack outputs for feeding external amplifiers as well as pair of auxiliary RCA phono input jacks to accept the output of an iPod (via a stereo mini plug to phono plugs adapter).
Vibrations in a 2006 S500
Q: My 2006 S500 has a vibration at idle that has been getting progressively worse. Is this something I can fix or should I leave it to my mechanic? Our S has a little over 50,000 miles on the odometer.
A: This sounds like a common and repairable issue.  Most frequently, the transmission mount begins to weaken after five years or so, transmitting driveline vibration through the chassis.  Transmission mounts are reasonably priced from your local dealer (especially with your MBCA discount) and swapping out the mount is straightforward, requiring a minimal amount of hand tools and drive-sockets. You will need to jack the car up fairly high to gain sufficient access, so be sure your jack stands are in good condition before you start.
Also, even though the manuals recommend you replace spark plugs on your car at or around the 100,000-mile mark, the Mercedes recommendation is actually based on either mileage or time, with an outer time limit of five years.  I would recommend that you also change your plugs at this point.  Doing so will help ensure proper combustion, which nets benefits throughout your car’s drivetrain and exhaust.
Supercharger Noise in a 2005 E55
Q: Our 2005 E55 is coming up on 75,000 miles and I have noticed more noise coming from the supercharger. Is there any recommended maintenance for the supercharger?  I have asked my dealership about preventative maintenance and was told there was nothing that needed to be done but I would like to double-check before something expensive fails.
A: In short, yes, there are items you can tend to that will prolong the life of the supercharger and ensure proper operation over the long haul.  If you are beginning to hear more noise, chances are the supercharger bearing is beginning to wear excessively.  You can source a replacement bearing from a number of eBay sellers; Nachi in Japan is the manufacturer. Swapping bearings is not terribly hard, but it does require some larger sockets as well as snap-ring pliers that you might not have in your toolbox. Often, the bolt that holds the clutch to the supercharger is affixed with Loctite, making removal a bit trying; this is one bolt you do not want to strip!  
While swapping the bearing, this is an excellent time to change the supercharger oil.  You’ll need to order a can of Mobil Jet A oil which is readily available on the Internet.  A medium-sized syringe and a foot or two of plastic tubing makes the job fairly easy.  The port is on the lower front left (driver’s side) of the supercharger and is identifiable by the 5mm cap screwhead.  Once the plug is removed, remove all the old oil with the syringe and tubing as best you can.  It does hold more then one might initially expect.  Once it’s drained, refill with the Jet A. If the oil looks particularly bad, you might change it once more during your next round of maintenance.
Jonathan Hodgman is the owner of Blue Ridge MB, a full-service Mercedes repair, restoration and performance shop in Atlanta, Georgia (www.blueridgemb.com  or [email protected]). He is an active member of the Mercedes-Benz enthusiast community and likes old cars, new ones and all models in between. Jonathan’s approach to his work is guided by knowledge, experience and a passion for Mercedes-Benz. This material was also reviewed by Pierre Hedary and Albrecht Stachel.