Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 10-09-2009, 07:24   #1
Registered User
Beausoleil's Avatar

Join Date: Jul 2007
Location: Potomac Shores, VA USA
Boat: Formosa 51 Aft Cockpit Ketch - "Beausoleil"
Posts: 565
Images: 1
Engine Coolant Expansion Tank Question

I'm finally getting around to plumbing the engine coolant connection to my recently-installed Isotemp water heater. My engine manufacturer, Westerbeke, recommends "if any portion of the heating circuit rises above the engine's closed cooling system pressure cap, then a pressurized (aluminum) remote expansion tank must be installed in the circuit to become the highest point."

The existing expansion tank next to the engine is plastic, but I suppose that's because it's connected to the expansion valve of the pressure cap on the engine. When the water heater is plumbed in, there's no pressure relief valve mounted near it, hence the need for a more robust expansion tank. Does anyone know where I can find such a valve, and more importantly, would it just be easier to bite the bullet and fork out more cash to Westerbeke for their aluminum expansion tank kit? Their water heater connection kit is already expensive enough! I'd hate to think what they charge for an aluminum expansion tank...

Cap'n Jon (KB1HTW)
S/V Beausoleil -1979 Formosa 51 Ketch
"If it's gonna happen, it's gonna happen out there." - Captain Ron
Beausoleil is offline   Reply With Quote
Old 10-09-2009, 08:46   #2
Senior Cruiser
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,052
Images: 12
It doesn't have to be aluminum. Get any old engine coolant tank out of a junk yard, plug off one of the inlets, mount it higher than the engine/water heater, put a new pressure cap on it and tee it into the cooling system using the other inlet (fill it with coolant, of course). This will now become your main expansion tank, and the one on the engine will just be part of the cooling system (so don't open the pressure cap on the engine or coolant will flow out from the header tank).

Hunt around old marina yards with junk engines lying around.

The plastic tank is for overflow, and can't be used as a pressurized header tank.



You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 10-09-2009, 09:28   #3
Registered User
anjou's Avatar

Join Date: Apr 2009
Location: Malvernshire, on the sunny side of the hill.
Boat: 50' steel canal and river cruiser
Posts: 1,905
I agree with colemj The plastic tank is only an overflow catcher and not rated for temps and pressures of normal engine running. You may have to change the spring cap on the old header for a non spring one and make the new one on the header a spring loaded pressure relief.
anjou is offline   Reply With Quote
Old 10-09-2009, 11:25   #4
Registered User
James S's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: Yemen & Lebanon... the sailboat is in Lebenon, the dhow is in Yemen
Boat: 1978 CT48 & 65ft Cargo Dhow
Posts: 5,816
Images: 139
I'm not so the water heaters exchange coils higher than the highest point of the engine cooling?
The coils on my Isotemp are on the bottom when its lying on its side...I installed it that way to avoid having any of its coils higher than the engine.
I think if the expansion tank is to be installed at the highest point in the system its main job is to be an accumulator type tank in which case it will be under the same pressure as your engines cooling system.
What happens when you open the coolant cap on the engine...does the coolant that is higher drain out?
There is a lot to be said for having the WH lower.
S/V Arctic Lady
I love my boat, I can't afford not to!
James S is offline   Reply With Quote
Old 10-09-2009, 14:02   #5
Eternal Member
Chief Engineer's Avatar

Join Date: Aug 2006
Location: North of Baltimore
Boat: Ericson 27 & 18' Herrmann Catboat
Posts: 3,798
I have seen boats with a simple header tank at the high is "Teed" into the incoming line to the water heater. The Pressure cap remains the same on the engine.
Chief Engineer is offline   Reply With Quote
Old 10-09-2009, 17:13   #6
Registered User
redcobra's Avatar

Join Date: Mar 2009
Location: Towson, MD Chesapeake Bay
Boat: Pearson 39 Yawl "ZigZag"
Posts: 516
Yep, had to do the same thing when I repowered. ALways wondered why the expansion tank was in the cockpit for the old westerbeke now I know. Luckily I didn't throw it away and just reused it.

redcobra is offline   Reply With Quote


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Plumbing / tank pumping question Cormorant Plumbing Systems and Fixtures 18 30-01-2009 15:34
newby question about tank size escapeartist Monohull Sailboats 9 22-10-2008 16:44
Decomisioning Holding tank question Alan Wheeler Plumbing Systems and Fixtures 75 17-02-2007 22:13
Voters Approve Panama Canal Expansion CaptainK Cruising News & Events 15 26-10-2006 14:47
Space Heating from Engine Coolant Sonosailor Engines and Propulsion Systems 16 02-12-2004 13:09

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 09:55.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.