oil pressure light

[9MAK]

i recently took in a 55 plate mk5 gti as a px and second day of driving it oil pressure light started flashing, i have fitted a new pick up and the car already had a balance shaft delete, the last owner also recently had the timing chain done but they used silicone on the vacuum pump, i replaced the gasket on that too and double checked that the oil galleries weren't blocked, i then changed the oil pressure switch too but the light still comes on, the engine sounds very smooth no noise from lifters etc and wen the light only comes on wen you've been driving for 30-40mins so i was wondering if it could be oil cooler? not cooling the oil efficiently and therefore causing the oil to go too thin? or could it be the valves in the oil filter housing?

[OllieVRS]

Get an oil pressure test kit, the only way to know if the pressure is really off and by how much. If it's after 30-40 min that's when the oil has really warmed up so I'd say it's genuinely got low oil pressure.

If you've checked the balance shaft ends aren't wiggling and nothing else seems wrong it could be the oil squirters (aka oil spray jets) under the pistons, on higher mileage/less maintained cars this happens. Mine failed at 125k miles with poor service history.

I actually made a DIY on this a while back, here's my post: https://www.mk5golfgti.co.uk/forum/index.php/topic,133731.0.html

Come back when you've got the 80 degree oil temp pressure numbers, at Idle RPM, 2000RPM and 3000RPM. I'll be able to help you more with that info.

EDIT: Almost forgot but there's another two things I don't think you've checked. If you disassemble the pump rotor you can check if it has any internal scratches or grooves that could leak pressure. And there's the Pressure Release Valve in the pump too, but this one's much harder to check. WASA Motor mention in a blog post https://wasamotor.com/2020/05/tfsi-2-0-ea113-oil-pressure-part-3/. They also sell their own fix, but it's a lot of DIY work so you might as well replace the pump at that stage. I just gambled that it was the oil squirters and I got lucky so I didn't touch the PRV.