Coolant overflow tank location

[Blue Nose]

I will be adding a coolant overflow tank to a 5424 Universal diesel. Should the tank be mounted higher or lower than the coolant reservoir on the engine?

Thanks

 

[Don S/V ILLusion]

higher, otherwise, gravity...

edited for clarity - if the system is sealed, it should not matter, however, in the eventuality of a leak in the cap, clamps, hoses, etc.., it's safest to mount it at or higher than the heat exchanger.

 

[Chuckbear]

It actually does not matter since the overflow and return acts by pressure and suction and not gravity. Pressure in the FW tank as it heats forces the coolant out and once the engine cools it is pulled back in. We try to mount it about level with the engine coolant tank as much as possible. Chuck

 

[Chuckbear]

I might also add the the best overflow tank is the type that feeds the water in from the top and has a tube which extends down to near the bottom of the overflow tank, rather than the cheap type you can buy from the auto supply store. Chuck

 

[Blue Nose]

Why is that style better than one that feeds from the bottom of the tank?

 

[Chuckbear]

Blue Nose, we have seen very few that feed from the bottom of the tank that did not leak. You have the fluid always laying at the bottom where the connection is and with most of these plastic tanks, it is very easy to use a clamp and crush the small plastic barb and it will never stop leaking after that. Ant the type I mentioned will work just as your fuel and water tanks do, through a pick up tube rather than a fitting at the bottom. Chuck

 

[Blue Nose]

That makes total sense. Thanks !

 

[Blue Nose]

Where can I find a top filling type tank and baracket?

 

[larryw]

Typically, diesels do not use overflow tanks because they are not pressurized to the same pressure as a gas engine cooling system. Diesels use an expansion space in the top of the system. Open the cap of a COLD engine, and the coolant level will appear to be too low, about as far as you reach with a finger, but this apparent low level is expansion room. If your diesel is gushing coolant when it's at op temp, there's too much of it in there.

 

[Chuckbear]

After 35 years in the marine service industry, with the exception of some old diesels, I have never seen one without an expansion tank, including all of my own. The type of tanks I have mentioned are available from some automotive supply stores, most all cars have these now, or you can get them from just about any marine engine supplier. Just don't buy the official Yanmar tanks they are waayyyy overpriced. Chuck