Where to put engine coolant expansion tank

[rikhall]

I am neither a certified mechanic nor the son of one. I did install my Yanmar 2GM20F. I also enjoy searching the web. Here are three pictures, for what they are worth:

From the web - http://www.alberg30.org/maintenance/...nmarphoto5.jpg

Here are two from my engine - I think mine were a bit high:

http://rikhall.com/Engine%20coolant%20tank1.jpg

http://rikhall.com/engine%20coolant%20tank%202.jpg

[preservedkillick]

Thanks Rik & everyone else for the answers.

Rik, I'd not seen that Alberg engine photo before. That looks like a great setup, but my Vitus takes up too much room. I did notice that the middle of the tank is about the same level as where the hose comes out of the heat exchanger.

I'm heading down to the boat now to take another look. I may end up relocating it in a cockpit locker

[Omatako]

Just to answer your question about the pressure cap on the heat exchanger - the pressure cap is intended to raise the pressure in the system and in so doing raise the boiling point of the coolant. That way, if you do get a slight overheat the coolant won't boil at 100 degrees C and it won't blow out of the system.

In the system on your boat, the pressure cap will allow normal expansion to go back to the expansion tank when the pressure in the system exceeds the value of the cap and the expansion tank will replace the coolant thru a return valve in the pressure cap when the engine cools. It is thus better for the tank to be at least at or above the level of the pressure cap.

Note also that if the pressure cap is removed while the engine is hot (for topping up purposes) the pressure in the system is relieved and if there is a tendency to overheat, it will be exacerbated by the cap having been removed because the hot engine will not be able to build the pressure back (no expansion). That is really the reason why it is bad practise to remove caps from hot engines and not only because you'll get scalded (which could also happen )