1999 Volvo Penta "WT" Models Workshop Manual, Page 208Get this manual
Circulating Pump Description
The circulating pump is manufactured specially for marine useIt is serviced only as an assemblyDo not replace with an automotive circulating pump
Inspection
1Remove alternator and power steering belts2Grasp circulating pump pulley and check end and side playTurn pulley to check for drag3Look for water leaking from indicator hole beneath pump shaft behind pulleyReplace pump if play, drag, or leakage are evident