Guys, I just posted the following in another thread.
Put a mechanical gauge on it, and check the oil pressure. If it's excessive it is sucking the pan dry. Also, windage does not come in to play at lower rpm's (typically under 6K rpm). A deep skirted block might nudge that down slightly, but our blocks are not deep skirted, nor are they capable of exceeding 6K rpms, so windage is not a factor. Nor would viscosity/oil effect oil pressure in the manner described in the OP. I offer the following and have disassembled the pumps to verify the source...
Guys, there seems to be a common thread when I start discussing oil leaks in these engines. I completely rebuilt my 82 1.6 about a year ago, and was not happy to see the recurring puddles under mine. However, the tendency for these engines to leak around the valve cover seals is routine - but it shouldn't be considered "normal". Here's why:
I build mostly hotrod and race engines (American Iron and a few diesels), so I decided to put an oil pressure gauge on my engine to check new pumps oil pressure. It was in the stratosphere at 80 to 100 lbs while cruising at freeway speed. My truck has the .75 5th gear and the rpm's are under 4K @ 70 mph. The oil pressure requirement on a full-fledged race engine is 10 pounds per 1000 rpm - stock engines is ~6 psi/1K rpm; meaning our engines should never exceed 40-50 pounds oil pressure. My Cummins dually rarely exceeds 45 pounds and leaks and oil pressure are not a problem - even after 250K miles...
I built a blown hemi years ago for a pro-street car, and installed a customers Keith Black "top fuel" pump as he had requested. In less than 5 minutes it would suck the oil pan completely dry and register zero oil pressure !!! Extreme oil pressure can destroy an engine. Obviously, the VW diesel is at the other end of the extreme, but high oil pressure WILL cause leaks in ANY engine. Exceed more than 10 lbs/1K rpms and you're running higher pressure than most RACE engines. .Think about it
I decided to dig in a little deeper, and I've got some photos I can post if anyone wants to see why our engines run excessive oil pressure - excess pressure that pushes too much oil to the upper end, flooding the cylinder head, resulting in leaks. Maybe it's a pure coincidence that the valve cover gaskets and seals are the most poorly designed gaskets on these engines.
I've commented on excessively high oil pressures in the past, and I'm pretty sure someone else has posted about this, so I took a used oil pump apart I had lying around; drilled out the spring retainer plate; and removed the spring and bypass piston, cover and gears.
Turns out the clearance between the bypass piston and bore in the oil pump is so tight, that even the smallest of debris causes the bypass piston to lock up. I had to force its removal, and both piston and bore were significantly scored.
I'm planning to pull the pan and pump on my trick in the next few weeks and I'm going to ream the piston bore to give another .002 clearance. I'm also going to check spring rate, and order a lighter spring to get this thing down to ~40 psi max at cruise speed.
I'll keep you guys posted, but I'd be willing to bet most of our oil leaks would be eliminated, or at least significantly reduced, if we can just get the oil pressures down to reasonable levels (10 psi @ idle and <50 lbs cruising - hot).
Southernman
