Recently I replaced the oil pressure switch on my 996 as it was leaking and the light had started to flicker at idle when the engine was hot. I replaced it with the usual Vauxhall Corsa/Opel/Agila variant. Still getting a bit of flicker at idle but only when the engine is hot. Anyway, thought I'd check the pressure today. With a cold engine I was getting 70psi at idle. Once up to temp this had dropped to about 40psi (the new switch must be a bit fruity if it's coming on at 40). Revving to 4000 took it up to about 85, maybe a bit more. Does this sound about right? I was surprised with the 70 at idle cold and wondered if it was a bit high due to stuck relief valve etc.
Pete, here is an extract from the 748 factory manual from 2002 "Oil pressure values: ● Cold engine: 1100-1300 rpm over 2.5 bar 3500-4000 rpm between 4 and 6 bar. ● Hot engine : 1100-1300 rpm over 1.1 bar 3500-4000 rpm between 4 and 6 bar. Too high a pressure may mean that pressure relief valve has jammed. Conversely, too low a pressure may indicate that relief valve has jammed in the open position or that spring is too soft or pump faulty. Problems with pressure may also arise from worn seals or engine. " Both the 999 and 1098s manuals state not to exceed 6 bar (87psi) with a minimum on tick over when hot of 0.8bar (11.6psi) I don't have a manual for the 996, perhaps someone else on here can confirm the settings for you Either way your numbers look very high at the lower revs
Cheers Denzil. I'm not hugely worried as it did drop down when hot and never got much above the 87psi limit at higher revs. I might check out the relief valve next oil change.
