oil coolers & tank usage after engine failure
 

Our 3.4 race motor suffered a rod bearing failure which lead to metal shavings contaminating both carrera coolers and the oil tank. I sent the entire cooling system out to get ultra sonic cleaned and flushed, tank, coolers, lines, thermostat etc. Before installing the oil tank I rinsed it out with a gallon of paint thinner. When I took the drain plug out I found more shavings on the plug magnet. I repeated this another 4 times, shaking the tank vigorously, and I'm still finding one or two metal flakes on the drain plug each time. While I'm willing to do this until there are no more flakes, I'm not convinced that there's not still some in there.
We planned to replace the engine oil cooler with a filter as a safety measure.

One opinion is that the coolers are fine to reuse and the second filter will pick up any crap. The other opinion is to toss both coolers & tank (smart racing tank) and start over.

Any race shop owners out there with a suggestion?

Check the coolers when you get them back from being ultrasonically cleaned. We have had some not so good experiences.

We put a "cleaned" cooler back on a fresh rebuild, i.e. rebuilt engine, new lines etc.. and found flakes in the oil and traced the source to the "cleaned" cooler.

I would take it up with the shop that did the cleaning-- I sent my engine cooler to Pacific Oil Cooler for cleaning and repairs and also my FABCAR oil tank- they can return them with the actual debris they remove enclosed so you can analyze it (e.g. is it bearing material, what). You don't say who did the cleaning but there is absolutely no reason for you to be finding material in the tank once it's been cleaned.

That said there is always going to be crap in the system, hence the factory including a filter in the pressure circuit on the 906 and later on the Turbo and the 964- engines. After a couple hours of operation you can cut the filter open and see what is happening. I don't think I would try filters after the tank-- isn't it true that the only pressure feeding the oil inlet to the pressure pump is the head pressure in the oil tank? e.g. Gravity feed, you probably don't want to interfere with that with a filter.

The coolers were done by pacific oil cooler and they did include the bag with the debris. The oil tank was cleaned by the race shop. They (the race shop) said they ran it through their ultra sonic cleaner, and rinsed it out a few times after that.
Since they painted the tank they suggested I run a gallon of paint thinner through it to make sure there were no paint flakes. That's when I starting finding old rod bearing flakes on the drain plug.

Since I just went through an engine failure caused by debris in the engine (according to the shop), I was pretty bummed finding flakes in the oil tank, and was this enough debris to damage the motor.

The also suggested replacing the engine oil cooler with a filter like the 3.6 motors for more protection.

I had my cooler X-rayed after cleaning to ensure no internal contamination.

Cheap insurance.

Who x-rayed it?

I had Parker X-Ray in East Hartford, CT do it.

They are an Aerospace NDT supplier and were recommended by a local engine builder.