Dear Doctor: I purchased a 2007 Chevy TrailBlazer SS. The engine has a ticking/knocking noise on start up. I'm told by the dealer that this is a normal function for the SS version that lasts until the motor warms up. The engine is the V-8 Corvette motor and has about 68,000 miles on it. I'm nervous about this condition. What is your opinion?

Dear Tim: It is not unusual to hear some engine when first starting on a cold start. The sound can either be from a hydraulic valve lifter, or piston-to-cylinder wall clearance. As the engine warms, the clearances change and get tighter and noises will usually disappear. The use of full-synthetic engine oil can in some cases quiet the cold start up engine noises. Either way the engine noise you are hearing is not a concern, and I would not be worried.

Dear Doctor: I have a 2000 Mercedes C230 and I'm experiencing an intermittent whistle noise coming from the front of the car. When I step on the brake or turn the wheel the noise stops. The noise may not occur again for weeks. Any advice?

Dear Carl: Noises, such as the kind you are experiencing, are usually caused from either a brake pad or backing plate scraping against the brake rotor. The technician will remove both front tires and inspect the brake rotor back sides for any shinny spots for contact against the backing plate. The technician will also check the brake pads and brake pad hardware for their conditions.

Dear Doctor: I have a 2000 Chevy Venture minivan. My windshield wiper system work properly to clear rain, but when I turn it "off" the arms go to an upright position on the windshield and do not reset down. Why? Also, I'm not getting a strong airflow from the vent. What would be the blockage? Finally, my headlights don't seem to be projecting to the car ahead in traffic -- they seem to be just aiming at the roadway.

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Dear Ed: Many GM front-wheel-drive vehicles have an ongoing problem with a broken eccentric that causes this problem. Sometimes an easy fix is to re-bend the small tab on the eccentric. GM also sells a replacement that has been updated. The eccentric is under the hood and visible as soon as the plastic cover is removed. On the airflow issue, poor volume can be caused from a blockage in the intake ventilation, or a faulty door in the heater box. For the headlight lens, they may need to be replaced. I can tell you that I use Sylvania Silver Star ZXE headlight bulbs when replacing burned out lights and always replace them in as a pair. The ZXE bulbs offer HID light performance at an affordable price without have to replace or upgrade any connectors.

Dear Doctor: I recall reading in a past column about the low profile rims and tires causing a harsher ride in late model cars. I have a 2014 Toyota Camry XLE V6 -- great car -- pretty smooth, quiet, and quick. The tires are size 255/55R17 Bridgestone Turanza. What size tires and rims would give the car an even smoother ride and would this affect how the car handles?

Dear Mike: I drove the 2015 Camry V6 XSE automatic, and yes, it was quipped with low profile tires 225/45R18 radials and the sport-tuned suspension. Our test car had a firm, yet comfortable ride. To soften the ride you would have change the tire size to a 16-inch wheel and higher aspect tire ratio, keeping the same outside diameter. You will also have to replace the four tire pressure monitors. But I would first replace the tires with the same size and use a summer tread pattern. This would enhance the ride and make the ride even quieter.

Dear Doctor: I recently bought a Recreational Vehicle and would like a recommendation on what crossover to buy for flat or dinghy towing with a Blue Ox hook up. Thank you.

Dear George: There are many vehicles that can be towed safely behind an RV. You first have to determine what kind of car or SUV you want. I suggest you go to the local camp ground and talk to other campers who own a large camper and tow a vehicle behind. I see a lot Jeep Wranglers being towed -- and the Wrangler is a fun vehicle to drive.