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James2016
James2016

Posted: Sat Mar 19, 2016 7:00pm

Post Subject: Expansion tank overflowing since pressure check

Hello The expansion tank on my engine is leaking the engine is a vetus 417. There was no problems for the first four months using then I had a service and they did a pressure check since then the expansion tank overflowed so I changed that and got a new one but after about four hours sailing the new expansion tank started overflowing any ideas on why this might be happening?

Tony-B
Tony-B

Posted: Sun Mar 20, 2016 7:37am

Post Subject: Expansion tank overflowing since pressure check

As you give no details about age the type of boat and cooling system plus the age of the engine it is difficult to give any sensible answer. You also do not mention any thing else done during the service apart from the pressure check. I will assume that this is a skin tank cooled engine, if it is not please come back. On the fact of it there is nothing that doing a service plus a straight forward cooling system pressure check would cause this so I think there was something more going on, especially as a pressure test was done ion the first place. This is not likely to be a part of a normal service. I suspect that either the coolant was changed so new antifreeze could be added or the pressure check found a leak and blew a lot of coolant out of the engine. In either case I suspect the cooling system was not properly bled fee of air so now you have air trapped in it. Probably in the skin tank and that should have bleed plugs/screws st the top. Air expands far more than water when heated and that blows coolant out of the pressure cap but the engine does not overheat until it has blown a lot of coolant out. This is the most likely explanation as you make no mention of overheating. If it does overheat as the coolant is ejected then check the hoses in case they left a clamp on one of them. An expansion tank that overflows whenever the domestic water pump is turned on, engine running or not, indicates a leak in the calorifier coil. This fault does not need the engine running. If there is a back story to this please come back with more information, otherwise try manipulating the large cooling pipes so any air trapped in bends can make its way to the engine or skin tanks and then try bleeding your skin tank.

James2016
James2016

Posted: Sun Mar 20, 2016 4:38pm

Post Subject: Expansion tank overflowing since pressure check

Hiya tony Thanks for replying The boat is an 8 year old, 57 foot narrowboat the engine is also 8 years old. When they service was done it was just a standard service but they did a pressure check to check for leaks and the problem started then. I got a new expansion tank like i mentioned but the problem still persists If you need anymore info please ask. Thank you for your help James.

James2016
James2016

Posted: Sun Mar 20, 2016 4:41pm

Post Subject: Expansion tank overflowing since pressure check

Also yes itis a skin tank cooled engine.

Tony-B
Tony-B

Posted: Sun Mar 20, 2016 5:23pm

Post Subject: Expansion tank overflowing since pressure check

We don't know what is causing it but the problem is that the water and whatever in the engine is expanding so much when heated it fills the header tank up and then overflows. Normally the tank would be large enough to contain the expanded water and then some more. Fitting an new tank would not be expected to cure such problems unless the pressure cap was faulty but even then the tank should still contain the coolant except it would boil at a lower temperature than normal. If that was the problem then just a new pressure cap of the correct dimensions and pressure should cure it. As you do not mention overheating my best guess is still air in the cooling system but I suppose it could be a symptom of head gasket failure but that should end up with overheating. Try bleeding the cooling system as I explained this morning.

Tony-B
Tony-B

Posted: Sun Mar 20, 2016 5:26pm

Post Subject: Expansion tank overflowing since pressure check

PS did you see my note about a broken calorifier coil? does it only overflow when the engine is running or will it overflow all the time the domestic water pump is turned on. It its the later then do not worry about bleeding the system.

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