If you cannot trust your suppliers to deliver flawlessly clean coolers, you have the filter after the cooler, just as Mazda did. Even if the cooler arrived clean, the installation will generate debris such as metal shavings from screwing in fittings, and bits of hose liner material. The fewer the number of items between the filter element and the bearings the longer the bearings will live. Cutting open the first filter element after break in and laying out the paper will open your eyes as to what could go through an engine without that element right in front of the bearings.
Lynn E. Hanover
In a message dated 4/7/2008 7:00:49 AM Pacific Daylight Time, eanderson@carolina.rr.com writes:
Basically, my understanding is that the filter would keep any thrash from a
blown engine from entering the cooler - which as many have pointed out is
almost impossible to get clean of all possible debris. I am not certain why
this apparently can not be counted on to stop the trash, but I will
certainly defer to Lynn and those with a lot more experience in trashing
engines than I have.