Troubleshooting wet sumping 911R
 

Axel http://forums.pelicanparts.com/porsche-911-technical-forum/345183-swb-911r-beginning.html is wet sumping. I have noticed a problem with low oil level in the tank, and a low reading on the gauge as well, which might be attributed to the volume of oil draining out of the tank into the sump.

I drove it to Werks 1 in Sea Cliff yesterday to address various oil leaks and some other issues (45 minute drive) and when dave drained the sump more than 8 quarts came out! I checked at the oil tank in the morning before heading out (a 1972 style tank with a single cooler and S oil console) and there was a good return to the tank when running. I'm concerned that the bottom end is full and not only causing windage but pressurizing the bottom end and causing my various leaks. Not to mention who knows what's getting to the cooler if the tank is running low??

Do I a check valve? (Rothsport or other) or are there other things I should be looking for?

The Rothsport check valve is designed to keep oil in the tank when not running and lets oil pass when motor is running. So I dont think that will help.

I am not too familiar with the 72 set up, I know its different. could there be a plumbing issue?

The only time I have ever see this problem was with a cracked oil pump housing. A portion of the scavenge flow was being dumped into the case, instead of sent back to the tank. The pump housing had cracked because of too-small oil-cooler lines.
DG

Ouch! that would not be good. Were you able to see the crack from the sump cover?

Probably could have if I had tried. It was cracked right through the bore where the driveshaft enters. But at the time I was baffled, never expected to find a split oil pump, and just tore the engine down.
DG

low oil level in the tank, too much oil in engine sump.

This is exactly what the Rothsport oil inlet check valve is made for.

http://forums.pelicanparts.com/uploa...1490224573.jpg

Tell us again what motor you are running? I haven't read the 11 pages in your link. But I agree there is some problem with your scavaging system. Oil pump, pump set up (oil by pass up date?), or scavaging oil lines.
A friend had a similar problem, his oil pump was broken.

2.7L 7R case, 4 rib 3.0 oil pump. 911R style (in front or the rear wheel) oil system with S oil console and a single fender mounted cooler. two thermostats. 2nd one is in the console shunting the cooler below 100 degrees.

I can see the pump returning oil to the tank. Also, the car has a breather catch bottle which was FULL of oil.

The scavenge side of the oil pump has about 75% more pumping capacity (it is wider) than the pressure side of the oil pump. That is how it clears the sump.

An anti-drain check valve will not help you..the sump is not clearing..you have a problem with the oil pump..sorrry

A few more thoughts:

Any chance you put the sump plate back on with the drain plug centered on the scavenge pickup?

Since you have a 4-rib pump in what was probably originally a 3-rib case, was pressure relief valve mod made?

Maybe pull the relief valves from the case and make sure they are working correctly.

What front cooler/lines do you have?

Oil in the breather, and your earlier mentioned leaks, are almost certainly due to overfilling/pressurizing the case with unscavenged oil.

I'll pull the pressure relief valves. The case is a 1977 911S case. #6272430 Am I right in remembering that the pressure relief mod isn't necessary after 1976?

The oil lines are racing style braided with a good cooler.

No flow issues there.http://forums.pelicanparts.com/uploa...1490267892.jpg

You're oil is draining back from DS tank to your sump via your worn or damaged oil pump.
Your issue is more than just adding a one way valve.

There is no pressure relief on the scavenge side of the oil pump. The capacity of the oil pump is much greater on the scavenge side than the pressure side.If you have an obstruction on the return side you can blow out one of the "O" rings on the pump or crack the oil pump. The other possibility is the pick up tube is loose in the oil pump body and not pulling very well from the sump. That still should not leave 8 quarts in the crankcase..unless the engine sits for a while and the oil tank bleeds down.http://rennlist.com/forums/attachmen...1350935818.jpg

Is it possible that if the "safety valve" is stuck that the pressure side is dumping back into the crankcase?

I need a way to figure out if the oil is running back through the pump with the motor off, or if something is happening with the engine running. This idea of splitting the cases on a motor with 1,200 miles on it is turning my stomach.

If the "safety valve" was open all the time..you would not have oil pressure AND the scavenge side of the oil pump has more capacity to remove oil than pressure side to fill.

"Wet Sumping" is a very unusual problem in a 911..unless something is broken or the engine sits overnight or longer.

It is not unusual to 8 quarts of oil in the crankcase after the engine sits for a while..very normal.

It is unusual if there is 8 quarts of oil in your crankcase immediately after shut-down

If this was my motor, before a teardown, I would remove the scavenge oil line on the bottom left side of the case and look in to see what is going on with the oil pump.

You can see the oil pump gears through that opening.

Pulling the sump plate would also be a good idea.

I'm not clear if this problem just showed up or if it was ongoing since rebuild. My friend had the same problem. Upon teardown his oil pump had loose nuts on the end of the studs that hold it together.

I've only put 100 or so miles on the car since acquiring it from Lars and I'm not sure if he noticed anything before selling it. Again, it only has 1,200 miles on the build.

When I brought it to Dave Hammer (Werks 1) he noticed the issue since he drained the oil a few hours after I drove it in. Previous to that, I can only tell you that I checked the return flow at the tank on startup and it looked normal. I need to check the oil level cold and hot to get a better read on the situation. I'm supposed to pick the car up in the next day or so.

After I wrote last night memory kicked in a bit. There were a whole series of technical bulletins issued 78/79/80 or thereabouts dealing with oil scavenge issues in the early 3 liter cars. And there were associated technical fixes including an add-on venturi plate at the oil tube/sump, different pressure relief pistons/springs, and a guide for the spring. I think the gist of it was that the 4-rib pump couldn't keep up with oil dumped in the crankcase during hi rpm operation and the oil pressure relief valve opening. This doesn't seem to be quite the same as your issue, but there may be some similarities and research on it might offer some potential clues.

Update, Although the car still drains oil from the tank to the sump faster than I would like, it is clearly pumping back to the tank when run, and draining the sump as it should. Engine stays cool and no real issues otherwise. I'm going to chalk it up to the oversized racing oil lines and call it a day.