Cold start oil pressure delay?

I noticed on cold start my oil pressure won't move for ~5 seconds. When it finally does start moving, it's accompanied with a rattling noise and an rpm drop. After that, it's fine until the next cold start. I found some older threads and some say it could be normal if the car sat for a few days, and others say it's not normal and could be causing damage. So I'm not sure which it is. Also I know my oil pressure sending unit is off since it's reading 2 bar with the engine off, but that shouldn't cause anything right? I took a video of it here: You Tube

It appears the needle moves fairly quickly once the car starts. My 01 C4's needle is at 0 but then raises to 5 after it starts. Seems and sounds normal to me but I could be wrong? Does it smoke at all on start up? Any knocking or strange nosies at all? If not, I wouldn't worry about it. Just my $0.02 worth.

First thing I would do is replace the oil pressure sending unit. Second would be to replace the oil pressure plunger/piston (whatever it is called) and spring with the upgraded one. See here for oil pump components #23, 24 and 5 http://www.autoatlanta.com/porsche-p...section=104-00 https://rennlist.com/forums/996-foru...ement-diy.html

Quotes source posts: 19399044, 19399102

I think normally on other 996 it should take only a second or less for it to start moving? There's no smoke, and no noises except the rattle when the oil pressure finally starts moving (7 sec in the vid). I'll try starting with a new sending unit and go from there. I know it's off and needs replacing anyways, but I wasn't sure if it could cause any issues.

I think you might be over thinking it to be honest......but having the new oil sending unit makes sense.....this way it's more accurate.

What Joe said. The oil pressure sending unit should not read 2bar with the engine off. Yes, oil pressure builds in 1 sec on these cars. The rattle, if it�s not the piston/spring, is something else entirely, and several 5-chain 3.4 engines make this noise. Could be tensioners, cats, etc. My car has been doing this for 7 years. If I drive off immediately and keep revs around 2,000, no noise. If I just let it idle, it rattles for a good 60-90 seconds.

So I replaced the oil pressure sender and I'm still getting the oil pressure delay. It reads correctly with the engine off now though. Also the oil pressure is only like 3.8 bar, it should be 5 bar+ on cold start right? Seems like there's still something going on. You Tube

Did you check the pressure relief spring and piston? The spring in particular....... -Eric 04 996

Quotes source post: 19419084

Not yet I'll try checking those next.

Up until this point you have been assuming the actual engine oil pressure was good. Why not hook up a "real mechanical gauge" to test the engines actual oil pressure to verify...?

Got the car back and issue fixed! I found this thread with the same issue and it turned out to be the oil filter for them: https://rennlist.com/forums/996-foru...l#post15773584 So I had the shop check mine and turns out there was a generic unapproved filter on my LN oil filter adapter too. Changed it to one from LN. Also had them check the oil pressure relief and they found the old spring was compressed a bit compared to the new one. Not sure which was causing the issues, maybe both, but pressure builds instantly now and reaches 5 bar. Thanks for the suggestions everyone.