The camshaft has a very important job in the engine. Using a series of lobes on a long shaft, it must spin and make contact with rocker arms or lifters to open and close the valves. The opening and closing of the valves controls the power stroke. The condition of the camshaft lobes, which have an egg-shape, determines the length of the valve opening and the duration. Since the camshaft sits near the top of the engine, it has a harder time receiving proper lubrication from the oil pump that must pump oil upward from the bottom of the engine. Fortunately, when a camshaft begins to wear, it can give off some signs that an observant vehicle owner can spot.
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Things you need
- Timing light
- Owner's manual
- Socket set and wrench
- Compression gauge
Listen for any abnormal noise coming from the valve covers or the top of the intake manifold. Remember that camshafts rotate at half the speed of the engine crankshaft. Place the metal probe of a stethoscope against the valve cover top or side, for V-6 or V-8 engines that have push rod engines. Position the probe over the intake manifold for engines that have overhead camshafts. Listen for any loud clicking or "clacking" sounds. Move the stethoscope probe up and down the length of the valve cover or manifold. Such a sound could denote a worn lobe on the camshaft that causes the lifter to slap. Noise coming from all locations of the camshaft length could indicate multiple lobe wear.
Change the oil if it appears contaminated or dirty. Oil that has lost its viscosity will wear the camshaft and bearings faster than most engine parts.
Place the vehicle in park or neutral and set the emergency brake. Raise the hood. Refer to your owner's manual to determine the position of the number one cylinder on your vehicle. Disconnect any vacuum source on the distributor and plug the line. Locate the timing marks on the crankshaft and metal tab on the engine block. Refer to your owner's manual for the correct timing measurement for your vehicle.
Hook up the timing light plug clip to the number one plug wire. Connect the timing light positive lead to the red positive terminal on the battery. Connect the black negative lead from the timing light to the negative terminal on the battery. Have an assistant start the engine. Read the timing mark that aligns the crankshaft and metal tab. Compare the reading with your owner's manual specification, which will read in degrees. If the reading calls for six degrees BTD (before top dead centre), and your measurement shows anything less, this could indicate a worn camshaft which has retarded (slowed) the timing.
Temporarily remove the coil wire from the distributor to keep the engine from starting. Remove all the spark plugs; keep the plug wires near their respective holes for proper reinstallation. Screw the compression gauge into a front spark plug hole. Have the assistant crank the engine over seven or eight times with the ignition key (start position). Mark the compression reading down in pounds. Test all the cylinders with the compression gauge and record all the readings. Any cylinders below 13.6 Kilogram will show a loss of compression. If all cylinders read below 13.6 Kilogram, the problem might be a worn camshaft, provided the piston rings and valves have not suffered wear.
Remove the inspection window to the front timing chain (or belt) cover if the vehicle has one. Use a shop light to look inside the timing chain cover. If you see any excessive slack in the timing chain or belt, it will indicate that the chain or belt has slackened due to wear, or that the timing chain tensioner has frozen in place. If you see no belt or chain on the interior gear or pulley, it means the belt or chain has broken or become disconnect. Such a condition will result in no valve action at all, and must be repaired.
Listen and watch the engine while at idle. A rough or stumbling engine could point to worn cam lobes that will not allow the proper opening and closing of the valves. Listen for any popping or backfiring from the engine during acceleration. If the engine has been tuned to specifications, including the carburettor and fuel injection, the problem could be a worn camshaft. If you hear a howling or grating noise originating from the top of the manifold, it could point to a warped or bent camshaft that has suffered overheating in the engine. A camshaft that does not rotate will result from frozen camshaft bearings that have suffered from overheating or low oil pressure.
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