Bearing destruction. Any idea what caused this pattern?

[cstreit]

Hey gang,

We recently found bearing material in the sump of the #15 race engine.

Upon inspection I saw some bearing wear that looks a little strange to me. As you'll see in the pictures, there are a number of "spot wear" areas that seem counter-intuitive to me. Any ideas what sort of failure would cause this.

Sure seems like oil-pressure in general then exacerbated by stuff plugging up the oil-journals, but I know the oil-levels were good and pressures were fine the whole time (according to the data logs anyway.)

[Steve@Rennsport]

Chris,

Looks to me like some FOD went through there. That may have been leftover material in the oiling system and thats not uncommon,...

I also see signs of corrosion; spots on that bearing shell.

[cstreit]

Steve,

I was hoping you'd see this thread.

It's funny, I found some bits in the case that didn't look like they came from any engine part. It's almost as if there was some stuff dumped in the oil-tank. I know I sealed off the tank and engine orifices while the system was out for the winter, but I'm beginning to wonder if perhaps I didn't miss something.

Those spots DO seem like corrosion don't they. This car has oil changes with high-grade Mobil-1 racing formulation (Special barrel I got from a friend at Mobil-1) nearly every 5-10 hours of operation so what on earth could cause that?

I guess an extremely good cleaning is in order. Looks like the bearings were sacrificial though and the crank was saved. By the amount of bearing flakes in the filter, it had been happening a while.

[Steve@Rennsport]

Originally Posted by cstreit

It's funny, I found some bits in the case that didn't look like they came from any engine part. It's almost as if there was some stuff dumped in the oil-tank. I know I sealed off the tank and engine orifices while the system was out for the winter, but I'm beginning to wonder if perhaps I didn't miss something.

If the engine was out for overhaul, the oil tank and cooler should have been removed for ultrasonic cleaning and all of the oil lines disassembled and scrubbed out.

Those spots DO seem like corrosion don't they. This car has oil changes with high-grade Mobil-1 racing formulation (Special barrel I got from a friend at Mobil-1) nearly every 5-10 hours of operation so what on earth could cause that?

Many race-only oils do not contain ANY corrosion inhibitors and few antioxidants as they are intended as one-use-only products. Any change in humidity and/or temperature is sufficient for condensation that, combined with the byproducts of combustion, makes acids and thats precisely what you find after sitting.

I'd recommend draining that oil after each event to prevent recurrence.

I guess an extremely good cleaning is in order. Looks like the bearings were sacrificial though and the crank was saved. By the amount of bearing flakes in the filter, it had been happening a while.

Yessir, I think you are right on all counts,...

[cstreit]

THe engine was only out because I was doing a trans conversion (915 to G50). OTher than that nothing was done.... Obviously now that cleaning is a necessity... Coolers, lines, crank, case, yada yada...

I spoke with my contacts at Mobil about this and they haven't seen this type of corrsion with this particular oil, however they going to look at the pictures and run an internal analysis of the oil for me. IN the mean time, it'll be flushed every event. Just more fuel for the waste-oil heater this winter.

[cstreit]

Well I found it...

#1 Rod bearing spun. Almost completely gone, nothing left but a paper thin shell. The crank bearing surface checks in spec, tomorrow I'll check the rod for ovality. Certainly the damage on the other bearings is as a result of the loss of oil pressure because of the spun bearing.

Now, why did the #1 bearing fail. More than likely because of a couple missed shifts in the last 3.5 seasons and a few 'caught it' money shifts. The bearing just slowly broke down untill the loss of oil pressure caused it to fail completely.... ...however I'd entertain other ideas!

[Steve@Rennsport]

Originally Posted by cstreit

Well I found it...

#1 Rod bearing spun. Almost completely gone, nothing left but a paper thin shell. The crank bearing surface checks in spec, tomorrow I'll check the rod for ovality. Certainly the damage on the other bearings is as a result of the loss of oil pressure because of the spun bearing.

Now, why did the #1 bearing fail. More than likely because of a couple missed shifts in the last 3.5 seasons and a few 'caught it' money shifts. The bearing just slowly broke down untill the loss of oil pressure caused it to fail completely.... ...however I'd entertain other ideas!

Generally speaking, #1 or #6 rod bearing failures are due to dirt in the system.

Debris and dirt, from anywhere in the system, will lodge inside the crankshaft passages and since the crank gets oiled from each end, thats where it remains to do the damage. One also finds such contamination inside the case oil passages which is why each & every oil galley plug must be removed at overhaul for proper cleaning.

The crankshaft oil passage plugs must get removed and everything scrubbed out when you find such things (as well as at overhaul time).

FWIW,....when 911 engine starve of oil (provided everything is nice & clean), it causes failure of the #2 or #5 rod bearing as thats the last part of the engine to get oil.

[cstreit]

Good insight Steve... I'd love to know where dirt came from.... Perhaps a careless moment on my part...

[Steve@Rennsport]

Things we learn over 33+ years,....

[HawgRyder]

I guess over the years I have become very paranoid.
When building an engine NO ONE is allowed to come within 20 feet of the beast.
If I leave the build area for more than a few seconds, I cover the engine or whatever part of it I am working on at the time with clean plastic sheeting.
For overnight sitting...the same plastic...taped...and checked for holes.
I had a lookie-loo bend over my engine one time...with a cigarette in his mouth...you know the rest...ash fell into the valve galley....he tries to brush it out...spreads it all over the place....disaster!!
I threw a 1" box-open at him...missed by a hair...he has never been allowed in my garage since.
I tore everything down...washed...and rebuilt.
BTW...cigarette ash is metalic.
A little paranoia is a good thing.
Bob

[JoeMag]

Chris -- sorry to hear about this... do you run the 964/993 engine mount type oil filter?