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Engine And Other Noises

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On: Thu, Sep 8, 2011 at 5:17PM | By: Peter C Sessler

Engine And Other Noises

There's nothing more disconcerting than hearing a new noise from your car, especially if it comes from the engine. More often than not, it means it's going to cost you. Still, there are some occasions when letting the noise continue won't hurt anything, provided you can put up with the annoyance of it.

This is a high pitched sound that can happen pretty much anytime. It can also happen when you steer the car or turn on the air conditioning, as this puts more strain on the belt. The cause is usually a loose belt; if the belt(s) is glazed, have it replaced. There are some sprays you can apply, but save your money and put it towards replacing the belt instead.

These are high pitched metallic clicking noises that usually emanate from the top of the engine. These sounds are typically most noticeable when you start the engine—which indicates worn lifters on engines that use pushrods—or it might occur only at idle. The clicking can get worse as you speed the engine, too. The cause can be badly adjusted rocker arms or, worse, a worn camshaft. A worn camshaft will cause the engine to run rough and your engine won't have the pep it used to have. Sometimes you can drive an engine in this condition for quite some time. On the other hand, the noise could also be a small exhaust leak or piston slap. Piston slap indicates a worn cylinder—in this case, drive the car until the engine dies (a heavier oil might quiet it down a bit, too).

These can range from a “tick, tick, tick” to a “pfft, pfft, pfft” or to an annoying “clank, clank, clank.” Exhaust leaks are usually fairly quiet at idle, the loudest when you accelerate and the quietest at a steady cruising speed. The cause can be a bad exhaust manifold gasket or, worse, a cracked exhaust manifold. You can usually spot exhaust leaks by the black soot deposits at the source of the leak. If the source is a bad exhaust manifold gasket have it replaced and, so too, a cracked exhaust manifold. A quick fix that sometimes works (but usually not for long) is applying high temperature silicone RTV on the leak.

These can be silent, because they are small, or a loud high-pitched whistle. Bad leaks will cause the idle speed to increase while small leaks can cause the engine to die when you put it in gear. Vacuum leaks can also be responsible for a poor, irregular idle, too. The cause can be bad vacuum hoses or lines, a bad PCV valve or another malfunctioning vacuum-driven accessory, such as a power brake booster. It can also be a bad intake manifold gasket or a bad carburetor base gasket on engines so equipped.

Burned valves, which most of the time are exhaust valves, will make the engine rough and no amount of tuning will fix it. You can usually tell by the uneven exhaust pulses—just put your hand over the exhaust pipe. Back-firing through the exhaust system can be another indication or backfiring through the intake can indicate a bad intake valve. On the other hand, a vacuum leak, a bad piston ring or even a hole in the piston can cause the same symptoms.

This is a deep thudding noise that comes from inside the engine. It can happen when the engine is cold or hot and it usually speeds up as you accelerate the engine. The cause is probably a worn connecting rod bearing. This means the engine really needs a rebuild, but you might try straight 50 or 60 weight oil. I once kept an engine going by adding 90 weight gear oil. Other piston related noises include the sharp metallic clanging a bad piston pin makes—heavier oil won’t help here, unfortunately.

A grinding whirring sound, similar to the one made by grinding skateboard wheels, can indicate a bad water pump or a bad alternator bearing. A bad grinding noise that happens only when you start the engine is probably a bad starter—meaning there only a few more starts left before it goes.

Tires are known to make their own noises, most typically a regular thumping sound that increases as car speed increases. This means that the tires are out-of-round and it can also be caused by a tire worn incorrectly because the wheels are not aligned. The out-of-round condition is usually due to a combination of cheapo tires and hitting too many potholes.

Front-wheel drive cars have their own specific noises. One of the most common ones is a clicking sound as you accelerate around a turn—this indicates failing CV joint. Once these joints start clicking, there’s no hope of them getting “better.” Replacement is the only cure.

All these sounds and noises are indications that something is wrong. Your car is trying to tell you something—and I hope you’re listening.


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