Engine Bay

[Alan Wheeler]

We bought our first canal boat last month and I'm enjoying finding my way around the boat, especially the engine bay.

The boat has a Nanni N4.43HD diesel, 4 cylinder, 43hp Kubota engine. I noticed the fluid level in a reservoir container raised above the engine was below the minimum markings on the side of the capsule. I assume this is the coolant recovery tank. The engine's manual states it should be topped up with clean water. Is this correct?

Many thanks for any technical guidance.

Alan

[Scholar Gypsy]

I think you need to be confident what this tank actually does. What is is connected to? It could be the expansion tank. Where is the pressure cap for the coolant system?

If it is part of the cooling system then ideally you would top up with a water/antifreeze mixture to match what you have already.

[Chewbacka]

Assuming it is coolant then it should be topped up.  However if the loss is due only to evaporation (example a slightly leaky pressure cap) then it is water that is lost and should be replaced by just water if you don't want to increase the coolant concentration as if you keeping adding coolant the concentration will creep up.  However in the real world if you start at say 40% it would take a very lot of top ups to exceed 50% which is the max.

Of course if you have a leak you should top up with coolant as if only using water the concentration will creep down.

If it is only about a pint, I would put in coolant and buy myself an antifreeze/coolant concentration checker from any car bits place.

Coolant does have a life as the corrosion inhibitors do get used up - blue stuff life is normally a couple of years, so unless you know what is in there and how old it is I would consider changing it. If doing it yourself, I would wait until it is warmer as it is not a nice job when cold.

[Tony Brooks]

"Coolant Recovery Tank" - never heard of it but if that's what the manual calls it then its 99.9% certain it is the coolant header tank, especially if a very small blob of the liquid it contains tastes slightly sweet or bitter, more so it the liquid has a red, blue, green or yellow tint to it. If so then As the Gypsy says it should really be topped up with a water & antifreeze mixture - no greater than 50 - 50 but could be down to 25% antifreeze, 75% water.

Make sure hoses from this tank connect to the engine cooling system in some way, if not it could be a central heating header tank.

If the tank only contains water (test with an antifreeze hydrometer) then you should really drain the system down and refill with A 30% to 50% (no more) antifreeze mixture because antifreeze combats internal corrosion.

Now the important bit re your question.

Absolutely no one knows the total cooling system volume on a given boat that uses keel or skin thank cooling so any advice or markings from automotive sources stand an excellent chance of being wrong.  Your boat almost certainly uses skin tank cooling and it will hold far more liquid than any automotive cooling system so ignore the marks. The best way to find the correct level to top up to is to fill it nearly to the top just once when its cold. Then go for a cruise. After a  while coolant will   pour out of the overflow. When the engine is nice and hot stop and let it cool down. Whatever the level is then when cold is the correct level. However as long as you can see coolant in the tank when cold it is fine and no damage can be done to the engine..

[mross]

Only to add that after doing what Tony says, if you can't find the level when cold ie it's right down well below the bottom of the tank, then you need a bigger tank.  The engine might have no water in its upper parts until the water gets hot.

[Alan Wheeler]

Thanks to all, you have been very helpful.