G'day Vstred,
I have to admit you and your machanic went about it the correct way to replace oil pump. I have a VE 08 SSV and only done 75000 and lost oil pressure. I didn't believe it and yes firstly did park up and rolled back home.
After that I replaced oil sensor, still no pressure. I put a manual gauge on it and no pressure.
(IF ANYONE WOULD LIKE TO KNOW WHERE THE OIL PRESSURE SENSOR IS BEHIND THE BLOCK UP THE TOP). You cannot see it but you can feel it on the rear right hand side.
Removed front bumper with plastics, radiator (left condensior in engine bay takes a bit of playing around with), removed all pullies, belts, bottom left tensioner and removed timing chain cover. (to remove harmonic balancer pully you have to pay to get the proper harmonic pully remover or modify a 20y old one. The harmonic balancer would be close to pressed on in factory with no bolt holes to use
.
After removing oil pump and closely inspecting the relief valve it was stuck open. There was genuine wear where it has been getting caught and finally stuck. Have a photo of relief valve but unable to post.
Got an oil pump from sprints as I didn't trust another genuine one. When fitting you will find its near on imposible to get bottom bolt in oil pump on suction pipe. There is post online with a chevy engine oil pump failing (same pump)
Sudden Loss Of Oil Pressure - 2007 Chevy Silverado Vortec 6.0L - YouTube
All i can suggest to people who come across this issue is find a way to use top bolt or you will have to remove sump.
After installing pump I found twice as what I thought was normal oil pressure. I hope not to many others will come across this issue but it seems like a normal issue with the genuine L98 oil pump.
Thanks again Vstred for posting your issue as it helped me solve my issue in a couple of days. I wouldn't go pulling off sump and go
Darcon666 way if you don't have time to muck around and haven't done any major bottom end damage to your engine.