Coolant tank very very thirsty - BMC 1.5

[Guest]

Had a similar problem of water loss, replaced the spring loaded filler cap. Problem solved. Suggest you try this first as it is cheap, quick and easy to do

 

5th

 

Once cured a similar problem on a car doing this - as you and Alan say cheap and cheerful and no great loss if it doesn't work.

[Bloomsberry]

I had a coolant leak last year. Turned out to be a leak in the skin tank into the canal and as luck would have it the level of the canal wasn't too far from the filling cap.

 

Still cost me 160 quid to get it out the water and have it welded up though.

[KJT]

You don't say if you have had the boat for a while and it has recently developed this 'fault' or if you have recently acquired the boat and you have filled the header tank and it is 'losing' water.

If the latter, then the amount of cooling water in the whole system is quite a lot when you take into account the skin tank. engine block. calorifier etc and there could well be a lot of expansion taking place normally.

It might be that your header tank isn't large enough to deal with the expansion. Does it continue to lose water or does it reach a level and then remain at that level? Is so, then topping it up will just cause it to continually blow out the excess. But if it reaches, and remains at a lower level, then it might just be the header tank is too small for the system.