TONY BROOKS

Tech­ni­cal Con­sul­tant

Canal Boat - - Ask The Experts -

‘Most in­stances of over­heat­ing are caused by fouled props, un­der­size skin tanks or ex­pan­sion tanks’

FOL­LOW­ING MY AD­VICE on adding an­tifreeze, a reader tells me Beta says it will not hon­our its war­ranty if a 50 per­cent an­tifreeze mix­ture is not main­tained in the sys­tem. Ap­par­ently this is be­cause Beta over­heat alarms are set for be­tween 95 & 100C and the en­gine needs that amount of an­tifreeze to raise the boil­ing point to over 120C.

I find the ex­pla­na­tion some­what per­plex­ing, be­cause the pres­sure cap on its own will raise the boil­ing point to over 110C; most in­stances of over­heat­ing on narrowboats are caused by fouled pro­pel­lers, un­der­sized skin tanks or in­suf­fi­cient ex­pan­sion tank ca­pac­ity for the coolant vol­ume in use.

As an­tifreeze re­duces the amount of heat the coolant can carry away, I would have thought hav­ing a high con­cen­tra­tion would be more likely to cause over­heat­ing. But any­way, check your en­gine man­ual to see how much an­tifreeze you are re­quired to use.

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