Ok guys, I am stumped. Since my LS swap is basically complete, I've been chasing a whining PS pump and can't figure this out. I tried old school "wheels off the ground, lock to lock" bleeding method - multiple times, with as many as 30 reps. I then went "new school" and got a mightyvac and adapter to pull a vacuum on the system. Everything I've read says you should pull about 20in of vacuum and let it sit for several minutes. I can't get more than about 14in and I can hear bubbles, it will drop to 12in and hold. Since I don't have a fluid leak from the box, pump, cooler or any of the hoses, I figure it's sucking air at the box return fitting but there's not enough return pressure to leak fluid - so I replaced that fitting and used loctite 545 for good measure. No change.
However, if I put a hose clamp just past that fitting, I can pull 20in and it holds pretty well (for several mins). If I pull 20in and then release that clamp, it drops quickly to 12in and you can hear tons of bubbles in the reservoir. I'm now of the opinion I must have a leak in the box somewhere on the low pressure side. I'm not sure if there's a seal somewhere that only sees low / return pressure, but if so that would seem to be a culprit here. Any insight?
However, if I put a hose clamp just past that fitting, I can pull 20in and it holds pretty well (for several mins). If I pull 20in and then release that clamp, it drops quickly to 12in and you can hear tons of bubbles in the reservoir. I'm now of the opinion I must have a leak in the box somewhere on the low pressure side. I'm not sure if there's a seal somewhere that only sees low / return pressure, but if so that would seem to be a culprit here. Any insight?