Q: What are the steps recommended by the manufacturer for adjusting valve clearance on Nissan Sentra?
A: The manufacturer recommends adjusting the valve clearance at the specified interval only if the valve train is making excessive noise. Begin by disconnecting the cable from the negative terminal of the battery. Next, remove the intake manifold on 2.0L models and the valve cover on all models. For manual transaxle vehicles, set the parking brake and place the transaxle in Neutral. Remove the Spark Plugs and position the number 1 piston at TDC on the compression stroke, aligning the timing marks. Measure the clearance of the indicated valves with a feeler gauge, noting that you will feel drag if the adjustment is correct. Record each measurement and compare them with the desired valve clearance specifications, noting any that are out of specification for later reference. Turn the crankshaft one complete revolution, realign the timing marks, and measure and record the clearances of the valves again. These engines do not use valve adjusting shims; if a clearance is out of specification, the lifter must be replaced with a new lifter of a different thickness to correct the clearance. Remove the camshafts to access the lifters, mark those to be replaced, and record which valve they came from. Measure the thickness of the center of the lifter with a micrometer. To calculate the correct thickness of a replacement lifter that will place the valve clearance within the specified value, use the formula N=T+A-V, where N is the thickness of the new lifter, T is the thickness of the old lifter, A is the valve clearance measured, and V is the desired valve clearance. Select a lifter with a thickness as close as possible to the calculated valve clearance, as lifters are marked on the underside for size. Mark the new lifters for their destination, lubricate them with engine assembly lube, and install them. After replacing the lifters, install the camshaft(s). The remainder of the installation is the reverse of removal, followed by reconnecting the battery and performing the necessary re-learn procedures.