Another MAN engine question - coolant problem or not?

[Deleted User YDKXO]

I have MAN D2842 LE443 V12 diesel engines on my boat. Last week we did about 150nm of cruising and, whilst checking the engines at the end of the cruise, I noticed a puddle of coolant under both engines

For reasons I don't understand, the header tanks on these engines have 2 pressure caps (marked with arrows on the photo below) and for both engines, the coolant leak seems to be coming from the overflow pipes coming from the outboard pressure caps only. There doesn't seem to be any leak from the overflow pipe from the inboard pressure caps on either engine

Anyone got any idea what's going on?

 

[BartW]

Mike,
I have the same happening om my 2 MAN's,
on both I have to refill a few liters of water, every now and then,
but similar quantity on each engine, and no worrying quantity,

I alway's considered this to be from the expansion of the "air" in the cooling water cirquit / reservoir when heating up, pushing and opening the pressure cap spring

I just top op with fresh water, from the tap in the engine room hose, no special cooling liquid
I do this at the same moment when I check oil levels
I learned this from the previous captain, who has been doing this for years...
but to be honest, never gave it extra investigation

 

[kashurst]

has it just been serviced/inspected? I guess that the header tank is just been overfilled a bit and its been blown out when the coolant has expanded. Check the level when it's stone cold and see where it's sitting. I have had various makes of engine do this, if I filled them to the level in the manual it got blown out. There after the actual cold level never varied, albeit sitting 1/2" or 1" below the marked or indicated fill point

is the inboard cap an actual pressure relief cap or just a sealed cap to make topping up etc easier?

 

[Den100]

I had a similar problem on smaller Man's and replaced the pressure cap that was letting by to the overflow pipe this stopped the problem and it has never reoccurred. Speaking to the Man agents they say it is quite common for the pressure caps to need replacing.

 

[AndieMac]

I had a similar problem on smaller Man's and replaced the pressure cap that was letting by to the overflow pipe this stopped the problem and it has never reoccurred. Speaking to the Man agents they say it is quite common for the pressure caps to need replacing.

Agree, don't hesitate to replace the pressure cap or even investigate the sealing properties of the old cap if it has been leaking.
Had a case recently with a new engine installation (not an MAN) gradually leaking coolant water, even after a new replacement cap. Turned out to need a small 'adjustment', a piece of daggy metal wouldn't allow the cap to fit correctly, but easily fixed in the end though.

 

[Deleted User YDKXO]

Thanks chaps. Still mystified why the pressure caps on the outboard side of both engines seem to have failed at the same time but will arrange for both caps to be changed

 

[Deleted User YDKXO]

Just to complete this thread, a MAN engineer has pronounced that the leak is simply the coolant purging itself after overfilling during the recent service and that it will find its own level. Not sure why such expensive complex engines in such an expensive boat don't have expansion tanks fitted but hey ho. Either way I have bought 4 new pressure caps and if the leaks continue, I will change them

 

[rafiki_]

Good luck with this. Sounds a credible diagnosis by the techie. Blew a small amount out of one of my Cats after a fill. Took 2 sheets of paper towel to soak up, so not a disaster.