I've got a '97 Saab 900 SE Turbo with 350k miles. Just replaced the head gasket on it. Now that I've got it back together there's a noticeable whine coming from the oil pump area. The whine is still there even with the serpentine belt off. (Video link: https://vimeo.com/218544188/f86017032e
I've tried replacing oil pressure regulator and spring, dropped the oil pan and checked the pickup screen for debris (it's clean), swapped oil filters, and pulled and reset the timing chain tensioner. I've also pulled the oil pump and visually inspected (replacing the housing oring and crankshaft seal). No sign of problems.
No luck. I'm out of ideas. Timing and balance chains were replaced 1yr ago with Saab OEM chains.
Any ideas on what I should check out?