Posted: Wed May 18, 2016 6:09pm

Hello, Having discovered that my 20 year old Eberspacher D4WSC is beyond economic repair, I have decided instead to use the inlet/outlet from my Thornycroft 80D to feed the (small) calorifier on my narrow boat. However due to space constraints (the engine bay is quite short and the engine sited forward) and previous position of the Eberspacher the calorifier is sited quite high up. This means that the top of the calorifier is approximately two feet above the top of the engine block. I understand that it is possible to fit a flat sealing cap on to the engine header tank and connect a pressure hose from the overflow outlet to an expansion tank which can be sited above the level of the calorifier, but is this height difference asking a lot of the engine water pump? The engine is currently cooled by two skin tanks of approx. 9cu ft of cooling space.

Posted: Wed May 18, 2016 6:53pm

What you suggest is perfectly possible as long as the engine filler neck is not worn or distorted. Another way of doing t is to fit a very higher pressure pressure cap on the filler neck with a lower but correct one on the header tank. In this case you would be advise to plump the feed from the header tank into a low down cooling hose ad get a tank with an extra connection for an air bleed hose (small bore possibly) that you would connect to a high point in the cooling system. The height of the calorifier is of little significance because water leaving the calorifier would be dropping and helping to draw water into thee calorifier circuit so assisting the water pump. You will have a potential bleeding problem so fit a bleed point to the highest calorifier connection. Just make sure the header tank level is a little higher.

Posted: Wed May 18, 2016 7:06pm

Thank you Tony, this is exactly what I thought. Excuse my ignorance, but I'm a little confused as to the description for a low down cooling hose, can you elaborate or am I missing something?!

Posted: Wed May 18, 2016 7:14pm

When you refill an empty cooling system you will want to direct the coolant into the lowest part of the cooling system so as the system fills it pushes the air upwards and out of the skin tank bleed, the "old" engine filler, or the bleed hose I mentioned above. Where this low level connection will be on any particular boat I can not say but I would be looking at a low down skin tank to engine hose.

Posted: Wed May 18, 2016 7:45pm

That's great, I've got it now. Many thanks.

Posted: Thu May 19, 2016 7:46pm

Just a couple of queries regarding this post if I may: As I am merely adding extra capacity in the form of a calorifier to the cooling system I assume it is not necessary to drain everything down and I can just top up with antifreeze/water as required. Unfortunately I don't have any of the original antifreeze left and can't remember the name of it, only that is was blue. Does it really matter what I top it up with bearing in mind I plan to change the entire coolant at the end of the season anyway? And finally, the instructions for my calorifier recommend the fitting of a blender valve between the cold feed and hot output to reduce the possible high temperature of the water. Is this a good idea bearing in mind the large capacity of the cooling system including the skin tanks? Many thanks.

Posted: Fri May 20, 2016 7:46am

Any blue two year life antifreeze should be OK, don't worry about brand names. If ordinary blue antifreeze is mixed with organic acid antifreeze, usually red with a 5 year life, then the corrosion inhibitors can precipitate out and block small cooling passages. I do not understand why the skin tank area has anything to do with blending the DOMESTIC water. If you are thinking the large area will prevent the engine getting very hot then you need to think again. The engine thermostat opens and closes to regulate the flow of water and thus the coolant temperature so the engine shoudl reach its normal running temperature with absolutely massive skin tank areas. The calorifier feed is usually taken from the engine side of the thermostat so will be fed with water at the running temperature than may well be close to 90C. You do not want your hands in domestic hot water close to that temperature. Using a blending valve will in effect give you more hot water but at a safe temperature.