Anyone with a P1 should consider replacing the heater hoses before they fail. Same thing with the radiator hose above the transmission. The plastic T connect will crack/leak. The coolant bottle will crack open due to age, heat and pressure. Replace if original. There is not any coolant level sensor on any P1 Volvo. Parts pics are from ipdusa.com 0:00 / 9:29 Volvo Webasto problems / Volvo diesel heater not working Fix Madman Car 16.4K subscribers Subscribe Subscribed 69 Share 48K views 2 years ago volvo webasto diesel heater xc90 JWQMMwu.