How to Clean Valve Liftersby Tom Pace
Valve lifters, or tappets, provide contact between the valves and the camshaft. Most modern engines use hydraulic valve lifters that depend on the smooth flow of motor oil through precisely-machined ports. When oil deteriorates, debris can clog the valve lifters and cause them to malfunction, resulting in a loud tapping sound coming from the valve cover. The first step to fixing clogged valve lifters is to flush the engine before adding new oil, and the valve lifters should be individually cleaned if this fails to fix the problem.
Flushing the Engine to Clean the Lifters
Open the oil cap on the engine and add the engine flush detergent. Use detergent that is approved for the volume of oil specified for your engine, as you may need to add more or less than the full bottle of detergent.
Start the engine and run it at idle for 10 to 15 minutes. Listen to hear if the valve lifter noise fluctuates more than usual during this time while the detergent loosens the debris and unclogs the lifters. Turn off the engine.
Lift the front of the car and support it on jack stands. Drain the motor oil and replace the oil filter. Add new oil according to your car's specifications and lower the vehicle.
Turn on the engine. Allow the new oil to circulate for a few minutes, then rev the engine periodically to listen to see if the valve lifter rattling has improved. If not, clean the valve lifters by removing them from the engine.
Cleaning Individual Valve Lifters
Run the engine with the car hood raised. Identify the faulty valve lifter by listening to the valve cover with an automotive stethoscope.
Remove the valve cover and the rocker arm, and cam shaft to access the faulty lifter. Label each bolt and part as you remove them to make reassembly easier. Remove the valve lifter retaining bolt. Turn the valve lifter and pull it out of the engine.
Wipe off as much oil from the lifter and remove the spring clamp to take it apart. Dispose of any oil remaining inside the lifter and lay out all the parts.
Clear out as much oil as possible from each component with a lint-free towel. Remove any fine particles from the spring and recessed areas with cotton swabs.
Soak the parts in a jar of kerosene for several minutes. Remove the parts from the jar and dry them off with a lint-free towel. Inspect them for any defects or deep scratches, which will require that they be replaced.
Insert the spring back into the bore and fill it with clean motor oil. Reassemble the valve lifter and soak it in a container of clean motor oil to allow it to fill as much as possible.
Install the valve lifter and torque the retaining bolt according to the manufacturer's specifications. Install the camshaft, rocker arm and valve cover. Run the engine and listen for proper operation.
Items you will need
- Clean engine oil
- Engine flush detergent
- New oil and oil filter
- Car jack and jack stands
- Socket wrench
- Automotive stethoscope
- Jar of clean kerosene
- Lint-free towels
- Cotton swabs
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- Nissan Sentra, Pulsar & NX Chilton Manual (1982-1996); Chilton Automotive Books
- Jupiterimages/Photos.com/Getty Images