Coolant change Fq ?

[Portofino]

Guessing when stopped water drains out of the bronze pump case or at least the pressure on its side drops to near zero .It needs to never exceed the oil inside pressure .
If left over time the Dir of travel of fluids is oil from the crank case out .......all good .
How ever if you empty to crank case oil during a change that +ve pressure is lost .Ok for a few mins while it’s topped up / refilled .

Then reflect a mo at the first start .......if the water pump self primed ready for off pressure beats the oil pump pressure wise momentarily or longer it may over stress that seal and form a continuity in the wrong direction.

Marcs valve gear again may be better designed in theory with a self prime system with looses its ability to self prime after the pump pick up / sump is drained .

Dont know .

What I do know is ours ( MAN ) the oil seeps back into the sump after shutdown wirh no priming .
So for a moment the top end can be dry before the oil circulates .You know the whole cold start thing waiting for the oil to warm and fully circulate etc .
I did remove a valve cap after 6/8 weeks without running and it was still wet in there .
How ever once after 3 months they were pretty dry .
That why I regularly start n run mine in the winter .....to circulate oil and refresh seals etc .

In theory all things being equal the MTU should out last MAN .In practice there’s far too many variables to make any meaningful distinction s in CAT , D12 Cummins etc . You have to judge each case on it’s individual merits and instal etc

Its all about history and prevention maintenance wise .

 

[markc]

PS: M, if you will find out what the reason is, I for one would be curious to hear it.

Here are the relevant pages from the Maintenance Manual

 

[Assassin]

Is that your own recipe, or was it recommended to you by a MAN engineer?
I never heard anyone suggesting partial refills.

Its common on many things, Aisin transmissions are a prime example; major problems are that they deteriorate over time and coolant/anti freeze contains corrosion inhibitors and these deteriorate, I would prefer to do a complete coolant change as removing all the coolant also removes pretty much of detritus it holds in suspension, and for refilling I prefer using distilled or de ionised water over tap water.

 

[Assassin]

However I am interested . It does seem like a plan and presumably can't possibly do any harm.

It can Martyn and this is the issue, and this depends upon several factors, it also works in the right conditions and can be beneficial so establish what type of anti freeze you use and its composition as I wouldn't want to see you trash your engines.

 

[Boat2016]

The build up of sludge you often see around drain points is good reason to remove bungs to drain off at the appropriate time, if worried about cross threading or damaging them I would employ someone who is competent to do the job, also the bungs are more likely to be difficult to remove if left for long periods untouched. Proof of proper coolant changes would be something I would expect to see when buying a boat.

 

[Portofino]

The build up of sludge you often see around drain points is good reason to remove bungs to drain off at the appropriate time, if worried about cross threading or damaging them I would employ someone who is competent to do the job, also the bungs are more likely to be difficult to remove if left for long periods untouched. Proof of proper coolant changes would be something I would expect to see when buying a boat.

I’d be really concerned if I saw any sludge of any kind any where in a IC engines coolant.
Its a bit late by then , something’s gone wrong in a closing the stable door after the horse has bolted kinda way !

Agree with accumulation of a fat invoice file to dump on the desk in front a prospective buyer .