Coolant change Volvo Penta kad32 - not to be neglected

[MartynG]

I changed the coolant in my kad32 engines in 2020. However I must have left some old coolant or crud in the system as the new coolant soon became discoloured .
To be honest the coolant change before that had been left 4 years which is too long.
So in recent times I ran over several weeks with just water in the system and changed that water a few times. This seems now to have flushed out the crud and I now have antifreeze mix back in.
The expansion tanks seem designed to collect crud but are a pain to clean out .
I hope the coolant will remain cleaner now but in any case I intend to change the coolant on an annual basis . The lesson learned being not to neglect the coolant changes.
I see a lot of KAD and AD engines with stained expansion tanks so I am perhaps not alone.

[Ianfs]

Interesting post Martyn.

The only experience I have with KAD32's is from a Sealine 34 where one of the engines had coloured coolant in the header tanks caused by a head gasket leak. However you are right, most of them have cloudy coolant for some reason.

What is it about marine engines that cause us to change engine liquids so frequently? My Land Rover, Yaris and Rav4 coolant change is certainly not as frequent.

[MartynG]

I have no idea why .
Must be age related rather than hours .
I don't think there is a head gasket issue - both engines much the same and no oil in the coolant .