As a follow-up, I wanted to let everyone know that the deterioration of the heat exchanger, whos tube bundle is made of bronze and housing is made of aluminum, was probably initially caused by the fact that I didn't know there was supposed to be a sacrificial zinc on the engine. In fact, I had been told that there were none and that Perkins doesn't use them. Obviously not true. However, I thought I had looked everywhere on the engine and couldn't find any. I, also, looked in the Perkins parts manual and found none, and no mention of any. Upon being told where to look, on a pipe between the heat exchanger for the engine, which is the one that was being eaten up, and the heat exchanger for the transmission, there was, indeed, one zinc, hidden at the rear of the engine below the air intake. It is merely described as a "plug" in the parts book. All the zinc had dissolved, thus the aluminum housing was the next item on the "less noble" list. I'll be watching my zincs carefully from now on. I don't want to go through this again!