Headlight bulbs
Q: I would like to replace the low- beam headlight bulbs on my 2005 E350 with brighter bulbs than the standard H7. Any suggestions?
A: There are several aftermarket options available to replace your current headlight bulbs with ones of higher intensity.
A Google search for “H7 LED Kit” will provide sources for higher intensity bulbs with either a heat sink or a small fan to handle the extra heat of the conversion. Any bulb with a standard H7 (PX26d) socket will work in your 2005-2006 E320/E350.
In addition, Amazon offers a variety of higher intensity (65W or 72W) bulbs.
The following manufacturers also offer options for 55W bulbs with a blue-white color output: Phillps CrystalVision; Sylvania‘s SilverStar and XtraVision offer a 55W bulb that fits an H7 socket (PX26d); and Hella lists a 55W bulb that fits an H7 socket (PX26d).
Back-up convenience battery
Q: I only drive my 2008 SL550 once a week or less. When I start the car, the following warning message lights up: “Convenience functions Temporarily Unavailable”. During that time, the seat heater does not work, steering wheel electric tilt is inoperative, etc. After the car warms up, all functions return to normal. Do you think it is time for me to replace one of the batteries?
A: All current-production Mercedes-Benz vehicles have a main battery and a back-up (convenience) battery. They do need to be replaced within 5-7 years (depending upon usage and climate). Here’s a practical tip: I have found that calling Mercedes-Benz Roadside Assistance (the number is usually on the inside of your glovebox door) you can have either or both of the batteries changed for less than the price a dealership would charge. The dealer’s labor rates are higher than the roadside assistance rates.
Tire size choices, Part I
Q My 2004 W240 Maybach came with 19in x 8in wheels fitted with 275/50R19 tires. This tire size is no longer available, so I am looking to replace with a close fit. A 285/45R19 is pretty close. It is slightly shorter in total height and circumference, but is also a little wider. Would this choice work?
AWe should first take a look at what the group of numbers that are used to specify a tire size actually mean. The first number – 285 – is the width of the tire tread in millimeters. The third number of the group – 19 – denotes the interior radius of the tire in inches, which has to match the exterior wheel (rim) radius. So the alternate tire that you are considering would fit your current rims, though it would be wider at the tread. The number that isn’t specified directly is the sidewall size, which instead is expressed as the aspect ratio to the tread width. In this case, the 45 of your replacement tire compared with the 50 of the original tire means – as you’ve noticed – that the replacement tire is slightly shorter in height, which means it has a slightly smaller rolling circumference than your original tire. Given that the tolerance between the tire and the interior of the fender on newer cars is smaller, there is a risk that the sidewalls of the replacement tire might rub against the suspension or body components. This would be especially evident on the front tires when turning. You would be better off going with the officially listed replacement tire for that car and wheel size of 265/45R19. The replacement will have a very slight speedometer error with the speedometer indicating a slightly faster road speed than you’re actually going.
Tire size choices, Part II
Q: My wife’s 2012 E350 wagon is in need of replacement tires. The car originally came with 245/45/R17 tires. Is it okay to increase the tire by one size without getting wheel well scrubbing or speedometer calibration issues?
A: You did not specify why it is you want to go to a larger tire. Usually this is to get slightly lower engine speed for a given road speed. However, upsizing always carries a risk of tires rubbing on suspension or body components and if the same aspect ratio is kept will cause speedometer error (showing a slower speed on the speedometer than your actual road speed—inviting attention from law enforcement). Other reasons could include having more traction in snow or changing the appearance of the car. If you want better traction in snow your best bet is to buy winter tires with rubber compounds that are suited to cold temperatures. There are two basic ways to find the tire sizes that are appropriate for your car: (1) Look in the specifications section of your Operator’s Manual, (2) Ask your dealership parts advisor for an appropriate tire, (3) Consult with your tire dealer or use the experts at Tire Rack to get an appropriate tire that will not cause problems. With Tire Pressure Monitoring Systems, ABS, and so many other electronic sensors in a modern car, it is important to have the right size tires on your car and to have all four wheels wearing the correct size tires. Good luck!
Erratic idle when starting
Q: I have a 1973 450SEL (the W116 with the M117 engine). When the car is started from cold the engine speed goes up and down from normal idle speed in 5-10 second cycles. Once it has warmed up it then idles at a steady rpm. What is the likely cause and solution?
A: The culprit is most likely the auxiliary air slide valve. The Classic Center has replacement auxiliary air slide valves in stock, although they are not inexpensive.
Thanks to Tom Hanson at the Mercedes-Benz Classic Center in Irvine, California.
Soft brake pedal
Q: After having the B Service performed on my 2011 SL550, I noticed that the brake pedal was soft and traveled farther than usual when I applied the brakes– in the past the pedal was always very firm. Although the brake pads and rotors did not need replacement the dealer said that the brake fluid had required replacement. What is going on?
A: It is very likely that the brakes were not bled thoroughly to get all the air out of the brake lines when they were last serviced. Air compresses; brake fluid does not. Even a little bit of air in the system will cause a soft pedal that will travel farther before providing solid braking. In an emergency, if this happens while you’re on the move, you can get the brakes to operate by pumping them quickly once or twice. But this is definitely a safety issue, so we recommend you return the car to the dealership and have them double-check the system. The Mercedes-Benz Star Diagnostic System or a simple test by the service advisor or technician will verify the root cause of the problem. If there is air in the brake lines, it should be easy to correct, or if it isn’t, the technician can figure out the real problem and correct that.