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Engine over-heated - not urgent


Col_T

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So, engine is a BETA BV1505, skin-tank cooled, and we did slightly more than 320 hours cruising last year with no engine problems what so ever. However, first cruise this year, nearly at the marina entrance and the over-heating warning buzzer sounded.

 

I've now learned how to bleed the skin-tank, that the skin-tank connections are not ideally placed (both are on the top of the skin-tank) and that the highest-point in the engine-cooling circuit is in the skin-tank to engine return pipe, which is where the air-lock occurred.

 

However, given that the engine was not run since mid-September last year, I don't understand what caused the air-lock to developer since then and the beginning of September this year. 

 

Any ideas?

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Corrosion, dissimilar metals in the static coolant after the corrosion  inhibitor has been used up, either generally, or more probably, locally within the system.  This generates hydrogen, just like in a house central heating system.  Then you have gas to collect somewhere awkward.

I bet it is OK if you use it regularly, though a coolant change or more inhibitor might be a good idea.

N

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Dissimilar metal corrosion caused by life expired corrosion inhibitors in the antifreeze is a possible cause; very much the same as you get with domestic radiators that need bleeding all the time.

The corrosion inhibitors commonly have a useful life span of between two and five years

edit - beaten to it by others?

Edited by Eeyore
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Thanks for info, chaps. 

 

I prefer the titchy leak idea, mainly because I paid a boatyard to flush-out the old (blue) anti-freeze/ coolant and replace with 5 year life-span (red) anti-freeze / coolant in 2018. I wouldn't have gone off that quickly, would it??

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13 hours ago, Col_T said:

Thanks for info, chaps. 

 

I prefer the titchy leak idea, mainly because I paid a boatyard to flush-out the old (blue) anti-freeze/ coolant and replace with 5 year life-span (red) anti-freeze / coolant in 2018. I wouldn't have gone off that quickly, would it??

There are a lot of dissimilar metals in  a typical boat skin tank cooling system so the corrosion inhibitors work very hard.  Much harder than in a car which is the usage the 5 year life bit is based on.   For the price of 500 ml of Screwfix central heating inhibitor I would just add it.  The antifreeze element will last indefinitely.

N

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