Easter Egg Hunt

Perkins 4-236 Expansion Tank

Eolian has a diesel engine, a Perkins 4-236.   Because this is a marine installation, there is no radiator (instead there is a heat exchanger), and therefore no expansion space in the radiator.  For the marine installation, Perkins created a cast aluminum tank to provide the expansion space.

Tho the engine is still in its prime, the tank is failing (galvanic corrosion because it is in contact with steel?  Probably.)

One more lead-in:  An expansion tank should be the high point in the system, so that bubbles and air trapped in the system accumulate there.  But Eolian has an engine-heated water heater which is mounted above the engine, making it the high point in the system.  Long ago I added an after market expansion tank at the water heater engine cooling water inlet, so that we would not accumulate a big air bubble in the water heater, drastically reducing its heating capacity.  Eolian does not need the expansion tank on the engine.

So the fix to the failing expansion tank is simple, right?  Just remove the tank.

Not so fast.  The expansion tank traps the engine thermostat against the casting it is mounted to.  With the tank removed, we will need something else to hold the thermostat in place, and provide a connection for the 1.5" hose that carries the water from the engine to the heat exchanger.

My first thought was to contact our local diesel engine supply house, looking for a Perkins part to bolt on in place of the tank to do just that.  No luck.  Apparently Perkins made that special water outlet casting (which bolts onto the front of the head making a right angle turn upward and providing a four-bolt mounting for the thermostat and the tank), just for use with the expansion tank.  It seems that all other non-marine installations have only a two-bolt mounting pad for a standard water neck/radiator hose connection.

I considered just making a flat plate that gets bolted onto the platform to trap the thermostat, and then drilling it to accept a standard small block Chevy water neck.  I am still considering this option.

But wait...  What do you mean non-marine Perkins installations?  Where else are Perkins 4-236 engines used?  Very little research revealed that the Perkins 4-236 may have been the almost-universal industrial small diesel:

• Taxi cabs
• Fork lifts (Hyster)
• Towed air compressors
• Towed welders (Lincoln)
• Industrial tow vehicles, eg luggage tow trucks on runway ramps (Clark)
• Farm tractors (Massey)
• ... and more

Water outlet casting, thermostat, and water neck

For all these other installations, it turns out that Perkins made a whole host of water outlet casting and water neck combinations, with the resulting water flow directed to the left hand side of the engine, straight ahead, straight up, to the right, and several angles in between.

Wonderful!  A whole new universe of possibilities has opened up!

I contacted my brother-in-law back in Indiana (thanks Tom!) who is an antique tractor collector, and he provided me with several contacts for Massey tractor salvage yards, many of which provided additional contacts...  you know how this goes.  Almost everyone I talked to was very friendly and curious about my problem ("Did you say the engine is mounted in a boat??").  Finally, I found that Massey (tractors) part no. 37762701 would provide me with a water outlet facing forward, and to which I could (hopefully...) bolt a Chevrolet small block water neck.  This part is available new for a cost ranging from £19, $57, to $295 depending on where you look.

Massey 37762701

But I continued the search, this time starting with Lincoln welders, which also used the Perkins 4-236 engine.  In the way of the Internet, that led me hither and yon, but surprisingly, I ended up on a forum where boat owners with 4-236 engines were discussing using JBWeld to repair failing expansion tanks.  And one of the posters mentioned Trans Atlantic Diesels, and that they sold a number of parts that addressed exactly the problem of failing expansion tanks on Perkins diesels.  One of the solutions they sell is a combination expansion tank, exhaust manifold and heat exchanger, made by Bowman.  This was more than I wanted or needed (I've already replaced the heat exchanger with a Monel one, and replaced the exhaust manifold with a stainless steel one), but that forum poster also mentioned that supplied with this kit was a part that bolted directly onto the existing water outlet, trapping the thermostat and providing a hose outlet going to the right side of the engine...

Exactly!

Oh. My. Gosh.  This is exactly what I started out looking for originally!  So I called them.  You'll want to talk to Sheri Alexander - she is by far the most knowledgeable about Perkins engines, and in particular the marine versions, of anyone that I have talked to in this long journey.  Yup, they have such a thing!  But the one they sell with the Bowman  unit is designed for 2" hose, and my setup uses 1.5" hose...  Sherrie said they'd fabricate one for me with the 1.5" outlet for no additional charge!  And when I called back to provide the Perkins part number for my thermostat, she was already downstairs talking to the fabrication shop!

The Easter egg hunt is over.  The second part of the story, the actual removal of the expansion tank and installation of the new water neck/thermostat housing, is here.

Easter Egg Hunt