1999 Volvo Penta "WT" Models Workshop Manual, Page 271Get this manual
4Generally Noisy at All Speeds: Check for low or high oil level in crankcaseHigh oil levels will cause oil foaming from the crankshaft and will force air bubbles into the littersLow all levels allow pump to pump air at high speedWith engine idling, strike each rocker arm above the push rod several sharp blows with mallet; if noise disappears, it indicates that foreign material was keeping check ball from seatingStop engine and place lifters on camshaft base circleIf there is lash clearance in any valve linkage, it indicates stuck lifter plunger, worn lifter rolier, or worn camshaft lobe
5Loud Noise at Normal Operating Temperature Only:
If lifter develops loud noise when the engine is at normal operating temperature, but is quiet when engine is below normal temperature, it indicates an excessively fast leak down rate of scored tifter plungerRecondition or replace lifter
Removal
1With air hose and cloths, clean dirt from cylinder heads and adjacent parts to avoid getting dirt into engineIt is extremely important that no dirt gets into the valve lifters2Remove intake manifoldRemove exhaust manifolds3Remove rocker arm coversDo not pryIf covers stick use rubber mallet and strike cover end to jar looseLoosen rocker arm nuts and pivot the rocker arm free of the push rods11509