Drive it forever
Q: I have a 1996 Ford Ranger that sat for about a year. I would like to fix it up. Everything was OK with it before it was left to sit. Now it has a rapping noise that I think is a stuck lifter.
I changed the oil and added Slick 50. This quieted the rapping, but didn't stop it.
Many people tell me to add a quart of kerosene, run the engine for 30 to 45 seconds and then change the oil again. They say that it will clean the engine and lifters and, if it is only a stuck lifter, it will free it up. If it doesn't work, then it is the camshaft.
Is doing this a good idea, or will it damage the engine? What else could be done to free up a lifter without tearing anything apart?
A: Hydraulic lifters can develop sticky internal check valves when oil becomes sludgy from sitting or not being changed at the appropriate intervals.
This allows oil to drain out of the lifter, preventing it from keeping the valve lash tight, which is what you are probably hearing at idle.
Sometimes a good dose of detergents can clean it out, sometimes not. Rather than kerosene, try a can of Marvel Mystery Oil. I'm not making this up - there are other engine-cleaning products, but I prefer MMO. You can leave it in the crankcase until the next oil change. You should hear some improvement in a week or so.
Slick 50 won't do you any good. In a pinch you could try a quart of automatic transmission fluid in the crankcase, but I'd change it in about a half-hour.
If that doesn't clear it up, try synthetic oil, which will pick up a lot of garbage inside the engine. Give this a couple of weeks too.
Ultimately you may need to remove that lifter and rebuild it or, better yet, replace it. You can't really inspect the camshaft without some major disassembly.
Q: I have a 1998 Oldsmobile Intrigue with about 120,000 miles on it. It has been a great car, but the two lowest fan speeds on the heater/AC don't work, and the higher speeds are often too strong.
Is this a problem with the switch or with the fan?
A: It is the resistor block inside the plenum. It is cheap and easy to replace.
Q: I have a 1989 Dodge Ram truck that has not been used for an extended period of time.
I think the old gasoline in the tank is the problem.
I smell a bad odor from the exhaust, and the engine is hard to start, especially when cold. It runs better when warm. I replaced the fuel filter, which worked for a few weeks, and used additives, but the problem remains.
Do you have any suggestions?
A: You'll never be able to diagnose anything with old gas still in the tank. Drain it and refill it with fresh gas, and add a can of Chevron Techron fuel-system additive.
Q: I have been told recently that regular downshifting when coming to a stop will cause the throw-out bearing to wear prematurely. I drive a 2005 Ford F-150 pickup, with standard transmission so I could downshift in an attempt to save on brake wear. I drive from 3,500 to 4,000 miles per year, mostly on local trips.
A: Throw-out bearings last a long time, almost always longer than the clutch disc and pressure plate, and they are cheap to replace when the transmission is out in order to replace the clutch. Consequently, who cares if it lasts only a hundred thousand miles or so?
I downshift manual transmissions, but not to save on the brakes.
I do it so that the transmission is already in the right gear when it is time to speed up again.
On the other hand, if you believe that you're saving money and extending the life of your brakes by downshifting, the amount you're gaining is minuscule.
Mike Allen is a senior editor for Popular Mechanics magazine. Questions should be sent via e-mail to driveit@nytimes.com.
