Cooling System Issue ?

[RichLech]

Need some expert opinion.......

 

Had a survey done on planned purchase over the weekend. Surveyor found a few relatively minor issues for which solutions are clear but there is one that is causing me concern.

 

The boat was built in 2005 and the engine is a Barrus Shire 45hp. The issue is that the cooling system header tank appears to be empty. Engine runs well and did not overheat on our 2hr demo run. Engine was last serviced Jan 2011 so I had mentally budgeted for a service which will obviously top the header tank up. However, my experience with other diesels in tractors and Landrovers is that header tanks generally do not need to be topped up, even at service intervals.

 

So, I'm wondering where the cooling water has gone. There are no obvious signs of leaks but the laft hand side of the engine compartment does contain a little fluid while the right hand side is bone dry.

 

I am on a steep learning curve; am I right in thinking that this is a sealed engine cooling system that serves the calorifier? If so, this must provide other potential leak points. Is there a secondary coil inside the calorifier and are these known to leak inside the tank?

 

Any advice/opinion will be most welcome.

[RichLech]

Supplementary question.....

 

The boat has skin tank cooling. Is it all one system topped up by the one engine header tank or are the skin tanks and engine systems separate with some sort of heat exchanger to transfer cooling from skin tank circuit to engine circuit.

[Richard10002]

What did the surveyor say about the situation and your queries? One would assume that he is familiar with the engine type, and the arrangement?

 

Ask the seller - What does he/she know about it?

 

Ask for the tank to be filled and run the systems for a few hours/days to see what happens?

 

Is there any water in the engine oil?

[Paul Evans]

It is possible that your "header" tank is actually an "expansion" tank designed to retain coolant as it expands when the engine heats up. The cooling system, which includes the calorifier coil and the skin tank, contains a lot of liquid. As the engine heats up, the coolant will expand and the surplus has to go somewhere.If you did not have an expansion tank, it would probably end up in your engine bilge. As the engine cools down and the coolant "shrinks", the contents of the expansion tank will be sucked back into the main system and you have an empty expansion tank. Can you watch this happening as the engine runs and then cools down?

Edited October 17, 2012 by Paul Evans

[MtB]

Loss of coolant indicates a leak. Where from is the hard part.

 

Once you rule out visible leaks then yes, there IS a secondary coil inside the calorifer and yes, these DO spring leaks although it is rare. However, the domestic water system running at 2.0 bar typically will force water the other way through a leak leading to over-filling and over-pressuring of the engine cooling system.

 

The other possibilities are the head gasket or water pump. A pressure test can be carried out on cars, so I expect the same can be done to a boat installation. My van mechanic also has some wizzy chemical test he can carry out of the coolant to determine if the head gasket is leaking.

 

Mike

[FadeToScarlet]

There's another possibility. On the heat exchanger, there's probably a cap with a pressure relief valve. Coolant can be lost if it gets over pressured, through this valve.

[Brin Morris]

I would top up the header if it only takes a pint or two the chances are it is used as an expansion chamber and the engine will find its running level which is why it looks empty. If it ran for 2 hrs and never overheated it will not be running with no water.

[OldGoat]

I've had the same problem with my Beta. It's raw water cooled with a heat exchanger / exhaust manifold cooling. Now quite standard - I believe.

It regularly chucked out about a pint and a half, which worried me because the heat exchanger tube assembly is uncovered. Adding a skin tank for river use made the problem worse.

Now I've fitted an unpressurised header tank and bing no more water loss (just have to remember not to undo the pressure cap on the engine.....

 

I've seen several boats with external header tanks, so I'm wondering if it's a usual problem - expansion volume is too small for keel cooled boats.

[Higgs]

I find it odd, that after a survey, the surveyor hasn't given you a full picture. A header tank should contain coolant. If the colour of the fluid on the engine room bilge is blue, it could be hose leak.

 

I've asked a question on this forum about the chances of a coil in the calorifier going and it can't be completely ruled out. It is potentially dangerous to have coolant mixing with domestic water.

 

Did the surveyor not try to top up the coolant system and watch the effect in the expansion tank then?

 

Can the surveyor talk to the owner and have your question satisfied, or even try yourself to speak to the owner.

[RichLech]

Thanks for all your help.

 

The surveyor only went as far as noting that the coolant level was low and thet he could not identify any leeks. He suggested getting the engine checked by a qualified marine engineer - advice that seems to be standard from other surveys I've seen. He did note that the engine ran well.

 

I'm not sure there was enough fluid in the engine bay to determine a colour.

 

I think (hope) the most likely explanation is the one offered by Paul and Brin above ie. that what I described as a header tank is actually an expansion tank.

 

Anyway, I going back to Pyrford Marina tomorrow (they are brokering the boat). I have already asked them to check with the vendor. I intend to get them to ensure the cooling system is topped up to the correct level and then to run the engine for a couple of hours while I am there. I can then check for leaks and fluid loss while the engine is at normal running temperature.

 

Thanks again for all the help.