Automania/Repair & Maintenance

Auto Questions And Answers For Week 40 Year 2001

by Bob Hagin

Q. How often should radiator hoses and heater hoses be replaced? Do you recommend replacing these hoses with original equipment from the dealer or aftermarket hoses from auto accessory stores?

A. In most cases, there's no set time or mileage on coolant hose replacement. Twenty years ago, a common recommendation was to change all the hoses that coolant runs through every 60,000 miles but over the years, advances have been made in the makeup of the hoses themselves as well as the chemical composition of coolants (antifreeze). Now most owner's manuals don't give a hard number of miles or the amount of time that should pass before hoses should be replaced but 60,000 to 100,000 miles is a figure that's used a lot. But I've seen them go lots further without a problem. Although some antifreezes are advertised as never needing replacement, it's best to change it every two or three years just to keep an eye on the condition of the engine's coolant hoses. I usually pinch radiator hoses to feel if they're getting brittle inside and twist the ends of heater hoses to see if they're fragile enough to break off. All the hoses should be replaced whenever the radiator is taken out for repair or replacement and the entire system should be low-pressure flushed (including the heater core) to get rid of the old coolant. In older cars, this could present a problem in that the heater cores are sometimes in as bad shape as the radiator. As long as the radiator hoses are cataloged for your particular vehicle and have the correct curves and bends built into them, it doesn't make much difference if they're original equipment or aftermarket parts.

Q. I have been in the habit of leaving my automatic transmission in overdrive except when driving up or down steep grades. I was under the impression that this would be less of a stress on my transmission than continuously switching in and out of overdrive. I believe this because on a different car I once had a transmission wear out prematurely when I used to switch in and out of overdrive. But a transmission shop recently told me that this would cause my overdrive to wear out prematurely. Also I was told that I should switch from the factory recommended 5-30 weight engine oil to 10-30-weight oil as my mileage approaches 100,000. Could you verify if what I have been told is correct and if so, why?

A. I know of very few drivers who continually shift manually between direct drive and overdrive in everyday driving. Modern automatics are sophisticated enough to shift down and up by themselves as the engine load dictates. Unfortunately, some brands of vehicles are prone to blow transmissions without help from their owners. One reader complained of going through three in his new domestic van before it hit 40,000 miles. Occasionally in the mountains of Northern California I shift into "D" (direct) on a very long uphill grade, but that's it. My feeling on changing to a different viscosity oil is that it can't hurt anything and it will probably make you feel better.

Q. What really happens to a vehicle if someone rams a potato up a tailpipe? Will it damage the muffler? Will it cause exhaust leaks inside the cab? Fortunately no one has ever tried to clog my tailpipe with a rag or a vegetable. Is it really a big deal or just a prank?

A. One of two things happen when an exhaust system becomes plugged solid. If the car is new and everything is tight, the engine slows down and stops since no fresh fuel can get into the cylinders. If the system is higher mileage, the exhaust pressure builds up to a point where it finds a corrosion-weakened seam in the muffler, catalytic converter or exhaust pipe and blows it out. I've seen catalytic converters that have blown off the vehicle when they were "poisoned" with leaded gasoline.