Break-in Oil Debris

[304065]

As anyone who's read Wayne's book or broken in a rebuilt engine knows, the first oil change following startup contains "millions of tiny flakes" of metallic particles caused by the engine's moving parts wearing in against one another.

I don't know for certain, but I would imagine that these particles originate at the cylinder walls, where the rings wear in against the cross-hatch on the cylinders, and the peaks on the cross-hatch wear down as the rings slide over them. Likewise, other bearing surfaces, such as the inside of the rod ends and rocker arms, probably contribute their share of particles.

On the inside of the case, at the parting line, squeezed-out 574 or other sealer can break off and fall into the case.

Some of this crud should fall into the sump below the level of the scavenge pickup, and is removed when the sump plate comes out. (owners of "modern" 1983- on engines have to rely on a drain plug). What gets picked up by the scavenge pump gets sent to the oil tank, where it runs through the filter before falling into the bottom of the tank, which also acts like a gravitational separator. But then it flows out of the tank into the pressure stage, and gets sent through the oil cooler if thermostat open, otherwise, into the main oil gallery feeding the bearings, and then through the cam oil lines to the valvetrain, where it falls into the oil return tubes and starts the trip all over again.



So here's the question: what damage is being done to the oil cooler, the main bearings, the camshafts and valvetrain, and other moving parts, during the break-in with the particulate being recycled?

Would it make any sense to replace the engine cooler with an oil filter, 906-style, with lines to an external oil cooler, during the break-in period? This would allow an additional filtration stage before the main bearings. In addition, much success has been reported with an oil cooler in the pressure circuit as opposed to in the scavenge circuit, probably due to the fact that there's less entrained air.

Has anyone actually done this? Or do the many filtration stages (pickup screen, spin-on-filter, oil tank) make this overkill?

[tctnd]

In my humble opinion, Wayne is incorrect in identifying these as metal particles. I think they are flakes of moly from the assembly lube. Years ago I panicked after draining the oil from my fresh new 327 and seeing all the sparkles. My friend added a dab of assembly lube to some new oil, warmed and mixed it, and it looked just like the drain oil.
regards,
Phil

[Jeff Alton]

Why not send out a sample of the break in oil to get anylised?? Great idea, I think I will do that when I start up my new motor!!

I will do this on the first oil change (after 20 min high idle) and on the second as well. That way I can add to the thoughts here with some imperical data.

Motor won't be fired until probably late July.

Cheers

[cstreit]

I actually think you're BOTH right. I suspect that the majority of the metallic reflection you see in the oil IS moly from the assembly lube. In fact i tell new-engine customers to expect it for the first 3-4 oil-changes and not to worry.

The stuff you see in the filter (ala flakes and "particles") are what Wayne refers to I believe in addition to the smaller stuff joining the Moly.

[mackskibum]

I'm not sure I see the concern here. If the scavenge pump sends the oil from the sump to the filter prior to the pressure pump supplying the rotating parts then the filter should contain the majority of the "damaging particles" as long as it is not in bypass due to being clogged. If you are running the engine for 15-20 minutes and then doing an oil and filter change you should be fine.

Anyone know what the specified Beta ratio of the Porsche oil filter is?

[Tom F2]

I read once that valve springs are the biggest contributor of metal shards in a new engine.

[g rad]

Just drained 10 quarts of GTX 29 w 50 after 20 min. first run...on new rings,and bottom end and new oil pump..etc...... Only three or four actual metal flakes in oil, and millions of what I think of as rebuilding bearing lube.... put one of those super magnets on the sump plate, during the total run, and have a definite 3/4 in. circle of very fine steel... not much.. but it was only for 20 min... Will leave the magnet on to check on next 200 mile change... gerry rad

[cgarr]

The best thing you can do is to filter the oil just before it enters the engine like on my 912, This is after the oil pump, thats what you need to do. If you want max life out of the engine then install an Accusump and pressurize the oil system just before starting when most the damage is done, and be done with it..

[Eagledriver]

Fortunately this doesn't seem to be an actual problem. 911 engines have gone through countless rebuilds and been driven for hundreds of thousands of miles with no wear problems on the pistons, rings, and cylinders. They only time contamination seems to be a problem is when a part fails such as a spun bearing.

-Andy