Lifters are also known as cam followers, or flat tappets. They can either be mechanical or hydraulic. Mechanical lifters are also called solids or tappets.
Hydraulic lifters are also found on almost all later-model engines with pushrods, and also on some OHC engines.
A new lifter will often have a small, shallow pinhole in its base. This hole is normal and is a mark left during hardness testing.
Solid valve lifters provide for a rigid connection between the camshaft and the valves.
- Solid lifters require a clearance between the parts of the valve train. Periodic adjustment of this clearance must be made.
- Excessive clearance might cause a clicking noise.
- This clicking noise is also an indicator of the hammering of valve train parts against one another, which will result in reduced camshaft and lifter life.
Hydraulic valve lifters provide for the same connection but use oil to absorb the shock that results from the movement of the valve train.
- If a hydraulic lifter is not able to leak down (leaking of oil) or does not fill with oil, a noise will be heard from the engine.
- Noisy hydraulic lifters are often an indication of an oil pressure problem.
After an engine has had many miles on it, often the intake and exhaust valves begin to leak compression. In addition, the valve lifters may be worn, causing the valves not to open as far as they should. Check for a loss of power.
Partial engine disassembly is required to complete the inspection. Refer to your vehicle's service manual for complete instructions.
- The lifter body should be polished and absent of any signs of scoring or scuffing.
- The pushrod seat should be polished and smooth. If the seat shows signs of a ridge, the lifter must be replaced.
- With your finger or a pushrod, firmly press down on the plunger of the lifter. Make sure it moves freely and with some resistance. If there is no movement or if the plunger moves easily, replace the lifter.
- When inspecting mechanical (solid) lifters, carefully check their bottoms and pushrod sockets.
- Wear, scoring, or pitting makes their replacement necessary.
- Also, check the lifters for dished bottoms or scratches, which indicate poor rotation.
Two examples of wear that results when a lifter fails to rotate on the camshaft lobe. Courtesy of Federal-Mogul Corporation.
- The normal wear path is off center with no edge contact between the lifter and lobe.
- If the lifter fact contacts the outside edge of the cam lobe, severe loading causes rapid wear of the cam lobe making the lifter face become concave.
- A concave lifter will wear the edges of a cam lobe.
(top) A convex lifter prevents edge loading. (bottom) A severely worn camshaft Courtesy of TRW, Inc.
A very common valve noise is caused by a noisy lifter.
- Sometimes this occurs when the engine is first started because a lifter has lost its oil while the engine was off.
- Whenever an engine is shut off, there will be some valves held open, putting spring pressure on lifters to bleed them down.
- When pressurized oil reaches the lifter, the noise goes away.
- If the noise goes away in less than 15 seconds, this is considered normal.
Some other lifter noises and their causes are:
- Intermittent noise at idle or low speed .
- This can often be traced to dirt in the lifter check valve or wear.
- Noise at idle that goes away at higher speeds.
- This usually indicates excessive wear between the lifter body and its plunger.
- This noise could also be caused by low oil pressure or too thin an oil.
- Quiet at idle but noisy at high speed.
- The oil could be full of air. This occurs when the oil level is so high that the crank whips the oil, filling it with air.
- It could also happen because there is air leaking into the suction side of the oil pump.
- Lifter noise at all engine speeds.
- Dirt or varnish buildup inside the lifter.
- Worn parts such as worn rocker arms or a cam lobe that is going flat.
- Insufficient oil supply.
- Oil too thin.
- Oil pressure too low.
Lifter crown can be checked by laying a straightedge across the face. If the straightedge does not rock, the lifter must be replaced.