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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 16 YEAR 2001
by Bob Hagin
Q. I have a 1995 Toyota 4Runner SR5-V6. I bought the car in the Fall of 1997 and until recently, I did not have it subjected to outside temperatures above 65 degrees since the car has been in Iceland for the past two years. During this past Summer when the outside temperature rose above 80 degrees and the engine was running at idle in stop-and-go traffic, the engine temperature rose quickly and would automatically cut off the A/C until it only blew warm/hot air. The A/C would not blow cold until the engine temperature fell back to the normal range which usually occurred after driving it without stopping for a while. If the outside temperature is less than 80 degrees or if the car is not in stop-and-go traffic at temperatures above 80 degrees, the A/C does not cut off and is more than adequate. I want to remedy this before the next hot spell.
A. The 3.0-liter V6 engine in your 4Runner wasn't one of Toyota's better designs. When a timing belt change is being made, it sometimes takes just short of a quarter of a stick of dynamite to get the front pulley off. But the other problem is more major. The 3.0-liter V6 has a weakness in the cylinder heads wherein they suffer a lot from blown cylinder head gaskets. When they overheat even slightly, it's usually an indication that one or both of the head gaskets are beginning to leak burning combustion chamber gas into the cooling system. Have your 4Runner checked for head gasket leakage and also check for radiator blockage. If modern aluminum/iron engines don't use at least a 50/50 blend of antifreeze and water, corrosion forms debris that plugs the cooling system.
Q. Over the last 10 years or so, I've noticed a significant number of Chevy and GMC trucks and vans whose front wheels do not track with the rear wheels. It's always that the front tracks is to the left of the rear, usually by about two inches. It is as if this offset is caused by hitting a curb with the front wheels. Over the last year or two there has been a dramatic increase in this problem but now it is with all types of cars and trucks. The problem is much more prevalent with domestics cars than with others but it is occurring with luxury cars as well as compacts. Aside from wondering about the durability of the front ends, it raises a safety question of whether these cars will be able to maintain a straight line under hard braking.
A. After checking for worn or damaged suspension parts, one of the first things I taught my front end alignment students to do was to check chassis integrity, if the chassis or frame is dimensionally the same from left rear to right front as from right rear to left front. If the chassis is slightly askew, the rear wheels won't track right and vehicle won't handle right. Many modern suspension systems are mounted on sub-assemblies that are bolted to the chassis and they usually have some wiggle-room for adjustment. Often these measurements aren't taken and vehicles go out the of the shop with crooked systems. I'm not sure this would affect hard braking but it could be tested on mid-speed runs.
Q. I've seen TV ads for chemicals to put in your gas tank to clean carbon. How does the carbon get there and what does it do wrong? I just got my first car, a Chevrolet Cavalier, and I want to keep it right.
A. Deposits forms in the combustion chambers and around the heads of engine valves when gasoline and/or oil isn't vaporized completely and the "heavy" molecules become semi-solid carbon. This carbon restricts the flow of fuel into the cylinders and causes power loss. It can also cause 'hot-spots,' which causes detonation. Those chemicals work fine but you don't have to overdo it.
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