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32-3 Coolant recovery tank

Filkee

Sustaining Member
Thanks to the hive

Amazon package is en route. Glad to have sparked a larger conversation. You guys are the best.
 

sgwright67

Member III
Ok, that all sounds logical. However, some boats have water heaters but no expansion tank. How do they manage, without spraying coolant when the pressure rises?
Still a mystery, I think. ☺️
Frank☺️

I agree, a system without an overflow tank in a pressurized system doesn't seem like a good idea, and likewise, operating a system designed for a pressure tank without the proper pressure cap is also a bad idea. Pressurizing the cooling system raises the boiling point of the coolant, reducing the possibility of hot spots in the engine creating vapour locks. Yes, you *can* run these systems without a pressure cap, but you significantly reduce the safety margin of your cooling system. Since marine diesels are designed to run continuously at 80% output, I would be very cautious about doing anything that might impact their design efficiency when it comes to cooling.

I would hazard a guess that a system running without a pressure cap or an overflow tank is probably also running with a lower temperature thermostat so that the engine coolant never (or rarely) reaches the point of overflow. (ie: maybe a t-stat designed for a RWC engine is installed?). Of course, you *can* do this, but combustion efficiency suffers - diesels are designed to run hot for best efficiency.
 

Filkee

Sustaining Member
Like A Hole In The Head

I got all excited and ordered one of the tanks from Amazon. When I got to the boat today, I realized there are TWO hose connections: IMG_1899.jpg
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
>>some boats have water heaters but no expansion tank. How do they manage...?

According to the thread theories, a remote expansion tank is not required if the engine "radiator" cap is in fact the high point of the system (heat exchanger, water heater, all related hoses).

Correct?

The theory also implies that: If you have a factory remote expansion tank, your water heater, or some other appliance, is "above" the pressure cap on the coolant reservoir of the engine.

So, owners of remote pressurized expansion tanks--is that true in your case?

I just want to actually understand these variations....


 
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Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
I have a water heater that is below the radiator cap of my Universal M25, and an expansion tank that is above it. I have never seen the expansion tank with coolant in it, but I know the system is full of coolant.
 

toddster

Curator of Broken Parts
Blogs Author
Just to state the obvious: A system with no expansion tank perforce must operate at higher pressure and temperature than one with. (Sort of, I know...) On most engines, this is controlled by the pre-set pressure-relief valve in the HX or radiator cap, which is a more vital and delicate piece of gear than it might first appear. The one on my boat seems to last about two years, but maybe that’s a sign that it’s time to acid-flush the block again? IIRC, the Atomic 4 wants a 5 PSI two-way cap, but it normally runs at only 160°F. Each engine should have a pressure specification for the cap. If it’s not a two-way cap, an expansion tank won’t work. None of our small tractor diesels have expansion tanks, I think. (Maybe the David Browning? I’d have to go look.) The radiator caps are one-way safety-release only. The Detroit Diesel I used to own did have one. The Beemer has no expansion tank and it is a royal PITA to purge that complex system and keep it happy. (High pressure and many, many possible failure points.) The previous owner didn’t realize that the pressure cap had failed and ruined the rest of the cooling system by the time that I rescued the car. Turned a five-minute twenty dollar fix into a months-long hundreds of dollars system replacement.
 
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David Grimm

E38-200
Heres my 2 cents of automotive knowledge. Liquid (coolant) when heated expands and needs someplace to go. Hence the recovery tank. Long before my time back in the 60's when the radiator cap pressure was exceeded coolant would just spill on the ground. When you got gas the attendant would check fluids and top off your radiator. Then the EPA stepped in and made the manufacturer's install recovery tanks to protect the environment from the ethylene glycol coolant. It was then learned that this had a positive effect on the lifespan of internal coolant passages and the radiator. The recovery tank lets coolant out of the system when expanded and hot but also lets it back into the system when the engine cools bleeding all air and OXYGEN out over time. With little to no oxygen in the coolant corrosion is kept to a minimum. The pressurized metal tank on our boats is a heat exchanger for fresh hot water. I assume all Ericson boats don't have one. However every boat should have a plastic non pressurized recovery tank.

Side note: Every diesel fire truck I have encountered over my 20 year career has had a coolant recovery tank.
 
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markvone

Sustaining Member
>>some boats have water heaters but no expansion tank. How do they manage...?

According to the thread theories, a remote expansion tank is not required if the engine "radiator" cap is in fact the high point of the system (heat exchanger, water heater, all related hoses).

Correct?

The theory also implies that: If you have a factory remote expansion tank, your water heater, or some other appliance, is "above" the pressure cap on the coolant reservoir of the engine.

So, owners of remote pressurized expansion tanks--is that true in your case?

I just want to actually understand these variations....

I have the original white with blue top Raritan hot water heater directly behind the engine. The can of PB Blaster is sitting on the blue top of it. The picture is taken from the front of the engine looking back at the water heater at the height of the engine's radiator cap on the exhaust water jacket. The engine cap is just to the right at the height of the top of the out of focus cylinder in the right foreground or, easier to see, at the level of the yellow and red 'PB Blaster' wording on the can - about 4 inches ABOVE the water heater top. The heat exchanger in the water heater is near the bottom of the water heater, well below the top level.

I have a sealed metal expansion tank just under the seat level (12 inches above the top of the HW Heater) that is in series between the HW Heater and the SW/FW heat exchanger. A tube from the cap neck of the metal expansion tank goes to the bottom of my plastic overflow tank.

Mark
 

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David Grimm

E38-200
In theory if your engine coolant system is completely blead of air and you never exceed the psi (bar) on the cap you would never need an overflow/recovery tank. However on a 110 degree day your motoring for 10 hours in 90 degree water and you exceed the psi (bar) on the cap the coolant will vent out and spill into the bildge. When the engine cools down you will need to top the coolant off at the highest point to maintain efficiency. If you had a recovery tank at the venting cap the system would draw back in when it cools.
 

toddster

Curator of Broken Parts
Blogs Author
Yes, but as I tried to point out while falling asleep last night, you would also need to make sure that you have the right kind of cap to control it.
See here.
 

Joliba

1988 E38-200 Contributing Member
? Two reasons for an expansion tank?

The purpose of a pressurized expansion tank is to increase the volume of pressurized circulating coolant in the system. This could make a coolant system more efficient, as there is a greater volume of fluid to absorb the engine heat. More of the fluid is out of the hot engine block and located in either the expansion tank, the water heater, or the heat exchanger at any given moment. In those locations, the coolant temperature is dropping thereby carrying away some of the engine heat. The practical location of these tanks with the pressure cap in a convenient high position in the lazarette may have influenced their installation in some Ericsons. I’m still not exactly sure how they determined which of our boats needed to have expansion tanks. On the other hand, recovery tanks, as all have pointed out, are always needed to catch and replace the coolant as it expands due to heating. A proper pressure cap that allows overflow into a tube, as well as return with “vacuum” in the system after the engine cools down may be located either on the engine or on the expansion tank that is part of the pressurized system.
Mike Jacker
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
I have a water heater that is below the radiator cap of my Universal M25....

The bottom of the water heater is below the coolant cap, the top of the heater is above it. The heating/coolant "coils" inside are likely somewhere in between.

20190331_195339.jpg

I couldn't get the stick completely level because of some hoses hanging from above--it's sloping downwards slightly (towards the engine) in this picture. Top of tank is about 2.5" above filler cap so maybe 3.5" above reservoir. The hoses to the water heater run even higher (but that may be because they are plumbed to the expansion tank).

20190331_203944.jpg

Cap on my expansion tank is 7psi.
 
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David Grimm

E38-200
Right. So a 16lb cap would increase the boiling poit to approximately 216 degrees Fahrenheit. Our engine is designed to run at 180. I've seen mine go as high as 220 at full throttle after motoring all day. If you take room temp coolant and bring it up to 180 it would be at approximately 16psi. Anthing over 180 degrees the cap would vent. There is a chart online.

https://www.google.com/amp/s/www.engineeringtoolbox.com/amp/boiling-point-water-d_926.html

If you increase your cap pressure you risk blowing off hoses, gaskets, water pump seals ect. I don't know what Universal spec psi is. I will check mine next time I'm aboard.

My metal expansion tank is higher then the engine heat exchanger cap. It is also higher then the hot water tank but no coolant makes it to the hot water tank. Just fresh water. The coolant only goes through the metal box (heat exchanger)
 
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Saullincer

Member I
I had the same tank with the same problem. The pressure tank and the overflow tank are not the same. I took my tank to the real radiator shop and they fixed it like new. Should last another 30 years. I also had them boil out and test the heat exchanger. along with a couple new pressure caps I think it cost me 125.00 or so. I also mounted the tank in the cockpit locker where I could fill it and check it. The cooling system is the most common cause of engine failure in my opinion after 36 years as an automotive technician (Mechanic).
 
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