First we need to determine if it's really a belt squeal. If you can catch it while it's making the noise, or better yet, if you can make it do it while you have a helper handy, sprinkle a little water on the belts while the engine is running. If the belts are indeed the problem, usually the noise will stop for a few seconds or it will get louder. The point is the sound will change.
If you have the older style V-belt, it is very common for them to appear to stretch after the first few hours of use. They don't really stretch. The sides that grip the pulleys wear down a little so they sit deeper in the grooves of the pulleys. That causes them to become loose and need to be readjusted once or twice. The newer type of multi-ribbed flat serpentine belts don't do that. Most cars that use that type of belt have spring-loaded automatic tensioners to keep the belt tight. The pivot bolts can become rusted and make the spring-loaded arm stick so the belt will not be held tight. With that style, you can tug on the belt, (engine off, of course), and watch the tensioner pulley move back and forth. Sometimes you can see the arm stick when you release the belt. With either type of belt, if you tug on it between two pulleys, it should only flex about a half inch either way. More than that and it is probably loose.
A power steering whine is much different than a belt squeal and will often occur when the steering reaches full left or right or when the pump has to work the hardest which is at low speeds and when standing still. That noise is the pressure relief valve in the power steering pump hissing and is normal but a similar sound will occur if there is air in the system. Air might have gotten in if they had to disconnect one of the power steering hoses while doing other repairs, especially the water pump. Air can take a while to work its way out. The best way to hurry up the process is by turning the steering wheel from full left to full right a few times when the engine and power steering fluid are warmed up.
A slipping clutch on an air conditioning compressor can cause a horrendous squeal too. The compressor runs in the defrost mode to remove humidity from the air before it is blown onto the cold windshield where it would condense. If the squeal stops when you switch the heater to floor or vent mode, check the AC compressor and its belt.
Tuesday, November 9th, 2010 AT 9:15 PM