Inconclusive autopsy

After disassembling and inspecting  Ms. Bettencourt's entire raw water cooling system, I have been unable to find any clear-cut cause for the old diesel's intermittent temperature spikes. I have removed, cleaned and reassembled the heat exchanger and removed the raw water pump and replaced its impeller. I have checked all the passages in the pump. All of the hoses are being removed and replaced.

I didn't think the heat exchanger looked too bad, but there was some sand in it and a scrap of broken impeller from some previous melt-down. A long soak in vinegar may have removed some occult scale and might improve performance.

The photo at right shows the pump with the (black) impeller I removed and replaced. The take-out impeller looks a little ragged, but, again, unlikely to be dysfunctional. I put the new blue impeller in the photo for comparison purposes.

 Here's a closer look at the old and new impellers.

The take-out impeller had been in use about 200 engine hours. The comparison impeller is a different brand, but otherwise compatible with the Oberdorfer pump. You may click a photo to enlarge if you would like a closer look.


The result of all this work will be a cleaned out a raw water cooling system with all the soft components and clamps replaced, and a neatened-up engine box. If the overheating problem persists, I can at least be confident that the cause is not in the raw water cooling system.

I am putting it all back together now. There will be a test run sometime soon.