To drain or not to drain

[moodymadness]

What is the concensus of opinion on whether it is best to leave antifreeze in the engine/manifold on a Bukh DV20 raw water cooled engine when winterising or to drain it from the engine etc to just protect those small areas that cannot be fully drained. I'm thinking about minimising corrosion to best effect i.e. with it in or with it out. Hope that makes sense.

Pete

 

[starboard]

Leave it in.....if you drain you will get a build up of rust that will flake away and block the coolant channels next season.

paul.

 

[RestlessL]

The procedure I follow for my DV20 is:
(1) change the anode.
(2) run copious amounts of fresh water through to flush the system.
(3) change the oil.
(4) run more fresh water, adding 2.5lts of antifreeze to the last bucket.
(5) seal the raw water input and exhaust.

I will then change the impellor and bleed the fuel if needed in the spring.

John

 

[VicS]

As said elsewhere best to leave the antifreeze in but make sure you really have got it in there. It will not go into the engine until the thermostat opens , it just whizzes through the bypass and out of the exhaust pipe, so it is essential to run the engine up to full temperature while recirculating the antifreeze mixture.

A wet engine full of air with corrode more than an engine left full of water, but of course just leaving full of plain water is not an option in any climate where temperatures are likely to fall below zero!

 

[samwise]

I did just the same with our DV 20. But as advised, you must run it up until the thermostat opens to get the anti-freeze in the right places. In my early days of boat ownerhsip I was meticulous in winterising the engine, but completely forgot about the fresh water system. Result, floorboards awash after a sharp frost froze the water in the pipes and shoved them off the spigots, dumping the tank contents into the boat. I have since learned the value of checklists!

 

[moodymadness]

Thanks for the advice which confirms my thoughts. I generally follow the above set procedure and also leave the fuel side until spring to avoid any possibility of wax forming in the cold weather in new filters etc.. Will also drain the 40 gallons of water I have on board and remove the pumps.
I just remembered when working in the automotive industry years ago and before 'all season' coolants were the norm that many of the older cars would have problems with head gasket failure within a week or two of adding the annual antifreeze mixture.

Pete

 

[Piers]

If it's a closed system, leave the coolant in for all the reasons stated above. However, a word of caution, make sure it is effective. This usually means changing it every three years before it loses its ability to antifreeze!