Building Too Much Heat
Q:I bought a new '01 Dodge Dakota with the 4.7-liter engine, auto, air, and the H.D. coolant package. The truck now has 45,000 miles on the odometer. Lately, I've been experiencing an overheat problem when climbing steep grades. The Dakota seems to operate at normal temperatures on the highway or stop-and-go traffic. On steep grades, it gets up to 245-degrees Fahrenheit, and once it got up to 250 after a 10-mile climb. Dodge has replaced the coolant, fan clutch, thermostat, radiator cap, and temperature-sending unit. The problem is still there, and Dodge says the other possibilities are a clogged radiator or a blown head gasket.
A:Testing for radiator obstruction requires the engine be at normal operating temperature (thermostat open) when a small amount of coolant is drained from the system. But here's a serious warning: hot, pressurized coolant can cause injury. Use a rag to cover the radiator cap, then open it slowly to the first stop to vent the pressure to the overflow tank. Once all pressure is released, you can remove the cap. After draining enough coolant to see the coolant tubes through the radiator filler neck, start the engine. At idle you should see the coolant passing through the tubes freely. If there's notable debris obstructing flow, you should reverse-flush the radiator before replacing it. Your best bet is to have it done by a shop with the necessary equipment. Testing for a compression leak at the head gasket involves the installation of a pressure gauge while running the engine and observing any fluctuation or rapid buildup of pressure. Without the gauge, you can remove the radiator cap, thermostat, and drive belt to inspect for bubbles coming up in the radiator after revving the engine a few times to approximately 3000 rpm. Here's something you might want to take into consideration while evaluating the high temperatures: The Dodge overheat diagnostic procedure states that a high-temperature gauge reading during towing or while climbing steep hills may be a temporary condition, and no repair is necessary if gauge readings are normal during all other driving conditions. Higher ambient temperatures and altitudes are also a factor in higher coolant temperatures.
Looking for Noise
Q:I purchased an '02 Chevy Silverado 1500 in January of this year, and it has 18,260 miles on it. I've noticed, when driving at about 45 mph and above, I hear rattling noises like something is vibrating. I've looked inside, outside, and even underneath and can't locate the sound. I'd appreciate any ideas on how to locate this noise. It's not loud, but it is loud enough to be annoying.
A:Vehicle noise can't be accurately diagnosed without being on-site with the appropriate equipment. Get an experienced technician to narrow down the possible causes. There are a number of tools available to aid in locating various noises and vibrations. I did a search for Technical Service Bulletins that may apply to the annoying noise in your Chevy truck. The only one that came close was in reference to a rattling noise coming from the center of the dash. The cause is actually a fuel line in the engine compartment on the other side of the firewall. The fix involves the removal of a cowl-retainer clip and the insulation of the retainer stud to eliminate the hard contact with the fuel line. This condition is typically heard only at idle, but I suggest telling the dealer (you should still be under the manufacturer's warranty) of the TSB I've just described. It may be a different problem the technician has come across before.