Changing Coolant

Sep 15, 2013
707
Catalina 270 Baltimore
Fellow Sailors. My water heater gave up the ghost last week. It started leaking from unknown places. I ordered a new one and this will be a good time to change out the engine coolant. My water heater is in a lazarette at cockpit level which is well above the engine. I have heard horror stories about trying to get the air out of the water heater circuit. Is there a trick I should know? I have a bleeder valve at the entrance to the WH in the lazarette. Picture below. After filling the engine I am thinking I should pre load the WH with coolant as best as possible and then close the circuit. Then run the engine and open the bleeder valve and add coolant to engine fill. bleed and fill, bleed and fill, repeat until there is no more air. Is it that simple? Am I over thinking this? As always all wisdom and kind guidance is greatly appreciated.
 

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Feb 26, 2004
22,759
Catalina 34 224 Maple Bay, BC, Canada
Is it that simple? Am I over thinking this?
Yes. No.
What that valve does is let air out at the high point of the system which is the only place air will get out of it, 'cuz the rest is filled with coolant, right?
It's great that you have that vent, go for it.
The larger question is where you put the coolant into the system if not the highest point.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Bawlmer, add a tempering valve while you are at it. Easier on the hands, and the hot water lasts longer, too.
 
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Feb 26, 2004
22,759
Catalina 34 224 Maple Bay, BC, Canada
The larger question is where you put the coolant into the system
@bawlmer
I looked at your photo again, and it looks like that is not a valve but a simple plug with a petcock "handle" on it, like a drain plug on a muffler. So that's a manual vent and also your fill port. Easy. Looks like you have a good system.
 
Sep 15, 2013
707
Catalina 270 Baltimore
I never looked that closely at the valve. I used it back in 2013 when I bought the boat to make sure there was no air in the system. There wasn't. I do not know if it is of sufficient diameter to allow fluid to be put in. I will check it next time. That would be a great fix though.
 
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Johnb

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Jan 22, 2008
1,419
Hunter 37-cutter Richmond CA
I never looked that closely at the valve. I used it back in 2013 when I bought the boat to make sure there was no air in the system. There wasn't. I do not know if it is of sufficient diameter to allow fluid to be put in. I will check it next time. That would be a great fix though.
If you have not changed your coolant since 2013 you may wish to consider putting it on a regular schedule.
 
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Oct 22, 2014
20,989
CAL 35 Cruiser #21 moored EVERETT WA
Bawlmer. Excuse the naive questions.
  1. Do you have a coolant reservoir on the motor?
  2. Is the valve higher than the coolant reservoir?
  3. Is the top of the valve above the Hot water heater?
Fluids will find level. If you add coolant to the engine and the level of the reservoir is lower then the heater, you will have coolant flowing out of the reservoir when you open the cap. Thus the "Nightmare" experiences you mentioned.

This is a system thing and you need to look at the whole system to find the desired solution. It would appear that if you can add fluid to what looks like a water hammer in a plumbing system with a valve, and at is the highest point in the system you should be ok. Just do not try to open the coolant cap. :yikes:
 
Jan 7, 2011
4,723
Oday 322 East Chicago, IN
My Yanmar leaked so much antifreeze, it sort of naturally got replaced annually.

she is fixed now, now more leaks...so I guess I ave to actually put it on my maintenance schedule ;-)

Greg
 
Sep 15, 2013
707
Catalina 270 Baltimore
Yup. Classic case of not fixing something that ain't broken. Shame on me.
 
Sep 15, 2013
707
Catalina 270 Baltimore
So. I got my water heater and its broken. The cold water input is cocked up to the point you can't get an adapter in to the threaded connection. I got it from defender so no worries.
 
Sep 15, 2013
707
Catalina 270 Baltimore
Update. Water heater issue resolved. I simply used a hose and funnel to fill up both hoses and WH before closing the loop. I ran the engine and burped a small amount of air out the bleeder valve. That was all I needed to do apparently. I will monitor the arrangement but it looks as if it is sorted out.
 
Sep 15, 2013
707
Catalina 270 Baltimore
The one thing I want to add is there are tailpieces out there with differing threads. For the Seaward water heaters you want the NPT threads on your adapter. That would be WM pn 1854546 for a 5/8 " ID water hose.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
If you add coolant to the engine and the level of the reservoir is lower then the heater, you will have coolant flowing out of the reservoir when you open the cap.
This isn't so. Coolant doesn't flow unimpeded from the system to the coolant reservoir, since there it is sealed at the top; if no air can enter the top, no fluid will run down.
 
Sep 15, 2013
707
Catalina 270 Baltimore
Yes. I have the expansion tank and it is a little higher than the water heater, which makes it fun to fill.