SCG Classic Car Troubleshooting Checklist - Noises that are not engine noises.
Noises Under The Hood
Squeaks, Squawks, Squishes
- Belts loose or glazed. This is almost always the problem, and to verify if a belt is creating the noise just spray some water on it to temporarily quiet the noise. Alternator belts can make noises when the electrical system is "loaded," and make no noises when it isn't. To simulate a loaded condition, turn on lights, A/C.
- Water pump bearings failing. Check fan shaft for movement up and down. If any is detectable, replace pump.
- Power steering pump. Pump itself can be failing or there is air in the fluid. To verify if noise is coming from pump disconnect the drive belt.
- A number of different sounds can come from accessories and their brackets. Buzzing sounds are common and are typically due to brackets that aren't tightened sufficiently. Rattles also are common and are due to improperly mounting the accessory to the bracket itself.
- It is very easy to "bottom out" a bolt in a tapped hole in the engine. In such cases a bracket will seem to be tight but actually be loose. Always double-check the length of mounting bolts before installing brackets.
- Many noises coming from the engine will exhibit themselves as external sounds. Crankcase ventilator valves (PCV) can buzz or hiss. To check for this condition, remove or pinch the vacuum hose to see if the noise goes away.
- Manifold heat control valves (heat riser) can rattle. If this is suspected, hold a screwdriver against the valve shaft to see if noise stops.
- Crankshaft end seals can squeak. If this occurs it might be necessary to remove the seal and replace it.
- Fuel pumps can become noisy as internal diaphragms age and begin to fail, or actuators may lose lubrication. The best way to listen for this condition is with a stethoscope or a long rod held to an ear.
- A whine or buzz in the radio is frequently due to electrical noise from the alternator. To test for this, remove the field wire to see if the noise goes away. Eliminating the noise is accomplished by either using an electrical filter in the power line to the radio or by replacing the alternator.
- Mounting hardware can rattle. If this is suspected, pry a screwdriver against the alternator with the engine running. If noise disappears, repair problem.
- Bearing noises are very common with alternators. Sounds vary from harsh, scraping noise to siren-like noise. Listen with a stethoscope or long rod at both ends of alternator. If bearings are defective they can be replaced, but many common alternators are available as rebuilt units for as little as $30.
- Alternator bearings can also make noise when extremely cold. If squealing sounds appear at 0-30 degrees F and go away once the engine is heated, bearing lubricant is insufficient. Replace the bearings or alternator.
Air Conditioner Noises
- Hissing immediately after shutting off engine (while using air conditioning) is due to refrigerant passing from liquid to gaseous state. This is normal.
- Squeal heard as compressor is engaging is due to faulty electromagnetic clutch. Most clutches can be replaced without removing the compressor.
- Belt noises are very common. Squeaks occur because belts aren't tightened sufficiently or are glazed over. Follow shop manual procedures when tightening A/C belts.
- Loose condensers can buzz or rattle. Check mounting hardware and brackets.