Engine Install, Do you need to prime the scavenger pump?

[cl8ton]

First, the turbo, scavenger pump, drip tank and oil lines are all stock and were not removed during the drop, the engine has 40k (original) miles on it and did not have the issue prior to the engine drop I am about to describe.

I dropped the engine 2 months ago for light maint work, after installing and starting it up and letting it run all looks fine with no oil leaks.

After cool down there is about 1/3 coffee cup of oil right under the turbo drip tank, I followed the oil trail and it starts at the gasket at the bottom of the drip tank tube under the turbo and runs down the tube to the tank where it then drips onto the garage floor.

I obviously thought it was the gasket between the drip tank tube that bolts to the underside of the turbo so I went about removing the allen bolts and replace with a new gasket.

After getting the 2 bolts out a lot of oil started spilling out from the opening of the drip tank tube?
As if the scavenger pump was not removing (sucking) the oil out of the drip tank and returning it to the main oil tank.

Anyone have any input to what’s going on here?

(I hope this is not one of them, “Gee I never heard of that before, let me know how it turns out” type of problems that I am famous for )

Thanks in advance, you all are a great resource!

[lucittm]

Rod,
I had the same problem, no oil leaks until I shut it down then a puddle. It turns out that any air (vacuum) leak will not keep the scavenge pump from pulling all the oil out of the tank but it will drain back after you shut down. My air leak was where the oil line goes into the pump at the 90 degree bend. It was rubbing on the exhaust heat shield and wore a hole in the brass pipe.

You will likely find a leak somewhere.

Mark

[cl8ton]

Thanks Mark…

When the engine was out I made special care to notice the 90 deg bend you spoke of which plagues many 964 owners.
All my lines were tight and oil free up to the turbo?

***sigh***

[cl8ton]

I was talking with a retired Navy Jet Engine Wrench/Sheriff Captain who is also my neighbor last night.

His words of wisdom were “Rod you are trying to solve an issue that does not exist! Button the dam
car up and take a spirited 30 min drive and the leak will be gone” He gave the technical reason why gear pumps
do not need to be primed, but assured me all it needed was a spirited drive to fix it.

I did and it was! Who knew? surely someone here knew this fact?

[smurfbus]

Welcome to 2020. I just had this same problem after braking the dripping setrab oil pan adapter for gravity drain to sump. Now after first drive with scavenge pump I had a puddle from the gasket plus a bigger puddle from my FULL catch can air filter that was low next to cyl6.

So forum says NO NEED TO PRIME? I think I will route the drip tank extra hose straight to oil tank and tee the filter above that line. But why did it leak like mofo today even driving as I smelled the fumed that came from 4-6 headers where some of the oil dripped.

[smurfbus]

Welcome to 2020. I just had this same problem after braking the dripping setrab oil pan adapter for gravity drain to sump. Now after first drive with scavenge pump I had a puddle from the gasket plus a bigger puddle from my FULL catch can air filter that was low next to cyl6.

So forum says NO NEED TO PRIME? I think I will route the drip tank extra hose straight to oil tank and tee the filter above that line. But why did it leak like mofo today even driving as I smelled the fumes that came from 4-6 headers where some of the oil dripped.

Edit: I take a bit back. Removed the filter and it was dry and it was the hose clamp from the rear breather to oil tank. Still the turbo gasket to drip tank still leaks so the oil is backing up some. But also the catch can was full so its either the breather hose or one of the catch can hoses and 90% sure its that blue hose to tank

[smurfbus]

3desiliter from catch can so seems like the scavenge pump is not doing its job.

[smurfbus]

I had to install a restrictor for the turbo oil supply. No more smokeproblems. Only now the turbo oil out gasket leaks even though it's new. Maybe double gasket or some sealant in it will help?

Heres a good post from Chris Carroll TK about oil flow from different turbos and what the stock scavenge pump can handle. I have a journal bearing Holset that needs a restrictor.

************************************
Here's our experience with the stock 930 scavenge pumps:

- They are really durable and typically last the life of the engine.

- They should be re-sealed when you rebuild/replace a turbocharger. They see some of the hottest oil, so it's only logical their seals take some of the worst wear. There's only a few seals:
* cover o-ring
* shaft radial seal
Plus the seals to the engine:
* radial seal for the air injection pulley housing (seals around camshaft's drive section)
* 3-bolt paper gasket to cam housing

- Most people skip rebuilding the pump when they do the engine because either
* they don't know it should be done
* they didn't know that little radial seal in the top end gasket set was for (the pump shaft)
* taking the driven cross shaft out of the pump is a bit of a pain because it gets pitted/deformed by the camshaft's 2 allen head bolts. (I've never seen one break, but plenty indented. Just file it smooth, tap it out, replace the seal, put it back together. A no-brainer.)

- The stock scavenge pump is sufficient for the K-2x series of turbochargers.

- The stock scavenge pump is sufficient for the Garrett GT-series ball bearing turbochargers, even in twin turbo applications.

- The stock scavenge pump does not pump enough volume for most other journal bearing turbochargers, including the T3 and T4 turbos, without restricting the oil inlet of the turbocharger. The exact size of the required restrictor varies per application (what turbo, what oil source, oil line size, engine oil pressure), but always run the largest one you can. Determining this is not difficult, just time consuming.

If you do not want to restrict the turbocharger oil supply, then a larger aftermarket pump is required. There are 2 versions on the market now, both based on the aftermarket oversize air-cooled VW oil pump. These pumps eliminate the stock 930 air injection pulley components (pulley, housing) and bolt directly to the camshaft housing. They usually require different oil lines in & out, too.
We are prototyping a few designs right now, too, available in Summer. Ours will allow the stock air injection pulley components to stay, as well as stock oil lines.
__________________
Chris Carroll
TurboKraft, Inc.

[TurboKraft]

Hi Smurf,

Yes, prime the scavenge pump if rebuilding it. Pack it with some assembly lube, or at least pour some oil into the outlet port.

We just had a 930 in the shop with a good functioning scavenge pump, and the 9mm ball bearing was present in the turbo oil supply atop the engine case. Still, if the car sat over the weekend, the compressor filled with oil. We converted the oil supply hollow bolt to one of our active check valves -- problem solved.