Only One Expansion Tank Now

(Part one of this story is here.)

Like with so many things,the preparation for this task far outweighed its actual execution.

Corroding cast aluminum expansion tank

There are only 4 bolts that hold the expansion tank on the engine, and they do not protrude into the water passage.  This means that they were not rusted or corroded - they were easily removed.  Loosening the hose clamp attaching the tank to the heat exchanger, and the tank was easily lifted out of position.  Far less work than I anticipated.

It's out!

...and the corrosion is worse than I knew

It turns out that the worst of the corrosion was at the hose attachment spud.  It was so bad here that I fear that I could knock off that spud with a sharp blow.  Good to get this failure point off the boat.

In an earlier post, I detailed the time and effort spent in trying to find a replacement fitting that would serve as a thermostat housing and provide a connection to the heat exchanger.  That search satisfied, I thought I was out of the woods.

Not so much.

Since I was in there, I know that my son would chide me if I did not replace the 40-year old thermostat.  So I started a search for a thermostat for a Perkins 4-236, 160°F.  Well it turns out that none of the diesel supply houses in Anacortes could provide one corresponding to the part number in my engine manual.  Or even in a cross-reference manual.

I thought that the thermostat looked very familiar. The one oddball thing was this little device:

Jiggle pin

I told you I did deep research...  In typically British fashion, it is called a "Jiggle Pin."  Its function is to allow air bubbles trapped below the thermostat to pass thru it when the engine is not running.  When there is water flow, the jiggle pin moves up and blocks the hole, stopping water from bypassing the thermostat.  A nice feature, but not strictly necessary, since once the thermostat opens, there is free passage for bubbles, which will then accumulate in the highest point in the cooling system.

I did find some Perkins thermostats.  In England.  For $50, not including shipping.

So I went to my local NAPA store.  I LOVE NAPA!!  No pimply-faced kid behind the counter that can't do anything without the computer (you should see their faces when I answer their question, "What kind of car is this from?" with "It's a Downeast 45 sailboat with a Perkins 4-236 diesel...  they are paralyzed) - experienced countermen who know engines.  I showed the thermostat to the counterman, and allowed as how it sure looked like one for a small block Chevy engine...  he went and got one off the shelf and with his calipers we compared the Perkins and Chevy thermostats.  Yup, the $8 Chevy thermostat is a drop-in replacement, tho without the (not strictly necessary) jiggle pin.

And then the second, and harder problem:  I needed a 1.5" hose that had one end expanded to 1.75" to fit over my new fitting.  And it had to have a right angle bend right past the expansion.  And a straight section at least 8" long to reach the heat exchanger.  Try searching for that on line!  The NAPA counterman took me into the hose room and gave me his calipers and left me to search.  It took me two minutes to find a suitable hose, a NAPA 8349.

What's left of the hose after I cut off the part I needed.  There are still a couple of useful bends there...

So, thanks to NAPA, in the space of 15 minutes I had solved both the thermostat and hose problems and was on my way back to the boat.  Can I say it again?  I LOVE NAPA!!

Done!

I ran the engine until it was hot, the thermostat opened, and the bubbles had accumulated in the expansion tank.  Job done!

Expansion tank, higher than the water heater

Only One Expansion Tank Now