Noises! We've all heard them at one time or another in our cars and trucks. Some are minor, and some indicate a need for major repairs. On the minor side: I remember driving my '48 Packard Custom 8 when I heard a noise coming from the front end--a clicking sound. As I listened more closely, the sound seemed to be rotational and was coming from the left front wheel, but it didn't sound like a bearing. When I got home, I pulled the hub cap and found a nut had come off the cloisonne hub cap medallion! I put the nut back on--problem solved!
Unfortunately, not all noises are that easy and inexpensive to fix. Pop receives a lot of e-mail requesting that he tell more about diagnosing engine noises, so we decided to do a Top Ten quick checklist to help identify the sounds. Here are some of the most common problems:
1. LOOSE MAIN BEARINGS. A loose main bearing can be heard and felt as a strong, dull, rotational knock, especially when the engine is pulling. The knock occurs regularly, every other rotation. To test for this, short out the spark plug wires on cylinder adjacent to the bearing. The knock will disappear or be less evident when the plugs are shorted. The test should be made at a fast idle. One of the main bearings called the thrust bearing is designed to keep the crankshaft from moving forward or backward. If this bearing is bad, it throws the crankshaft out of alignment and can cause it to hit the block.
2. LOOSE FLYWHEEL. This noise is usually an irregular clicking sound. A test is to fast idle the engine up and shut off the ignition. If a thud is heard and felt, this might be the problem.
3. LOOSE ROD BEARINGS. This can be heard as a tinny knock, as opposed to the deep thud of main bearing failure. It is most noticeable upon deceleration, but it can also be heard with the engine idling. To find the bad rod bearing, short out spark plugs one at a time. The noise will be reduced when the affected cylinder is not firing.
4. PISTON PIN NOISE. This sounds similar to valve and tappet noise, but it has a double knock and is loudest during idling. Causes can include a loose piston pin or inadequate oil. Knocking generally increases when the affected cylinder is shorted out.
5. VALVES. There are many things that can go wrong to produce valve noise. A clicking might be heard if there is too much tappet clearance, or a hydraulic tappet is not working correctly. Excessive clearance between the valve stems and guides can cause noise and will result in loss of compression and excessive oil consumption. Other problems with valves can be caused by too little valve clearance, causing the valves to hang open. Also, carbon, sticking valves, weak or broken springs, worn valve guides, rough cam surfaces.
6. HYDRAULIC LIFTERS. A clicking or tapping noise almost always is an indication of a malfunctioning hydraulic lifter. Some noise is normal when the engine is cold, but this should disappear as the engine warms up. Some of the causes of hydraulic lifter noise can be dirty oil, inadequate oil pressure or improper oil weight, water in the oil, too low or too high oil level, or incorrect initial adjustment. If just one lifter is noisy, it should be removed and inspected for wear.
7. FUEL PUMP NOISE. This can show up as a ticking sound. We use a stethoscope on the fuel pump to help isolate the noise. A simple test can be made by removing the fuel pump and putting a plate over the hole and running the engine with the fuel thats left in the carburetor. If the noise is gone, it was probably the fuel pump.
8. WATER PUMP NOISE. This is usually a squealing sound, and more times than not, it is caused by letting a car sit. When this happens to our cars, we add a water pump lubricant to the radiator and the noise usually goes away. If it doesnt, the problem could be a loose water pump shaft, loose impeller, too much end play in the pump shaft, impeller blades rubbing against the housing, or other internal pump problems, in which case, the pump must be removed and rebuilt.
9. SPARK KNOCK. This is a ping or chatter, mostly noticed during acceleration or when the engine is under load. It results from excessive carbon deposits in the combustion chamber, fuel with too low octane rating, or advanced ignition timing.
10. EXCESSIVE CRANK SHAFT END PLAY. A sharp rap at idle or higher speeds is the symptom of this problem. The sound should disappear when the clutch is disengaged. This can also cause torque converter trouble and excessive pump wear on automatic transmission cars, especially Buick Dynaflows.
These are just some of the most common engine noises and problems, but this Top Ten should provide a quick check, and might help pinpoint an ailment before tearing into an engine. See you next month. Keep 'em driving!