Pressurised cooling systems

[ianc1200]

I'm trying to understand the pressurised system my Nanni has; in general does the header tank act as a expansion tank only, or should you see the coolant in it? It's a semi clear plastic tank about a metre above the engine, and has a line about a third up from the bottom marked "coolant leveL" (from which I believe I should fill up to to this line). If I open up the radiator type cap on the heat exchanger & fill up, then do the same with the radiator cap on the header tank, does the coolant in the header tank play a part in ensuring there's enough coolant or sufficient pressure in the system?
The reason for asking is Nanni/Peachment's supply a "river plate" or cold running kit for engines running under insufficient load to heat up the calorifier. This was working fine at the end of last season, but for some reason this year with the river plate in the temperature creeps up to 95 degrees or so. The engineeer at the yard feels I shouldn't be filling the header tank to the mark, as it is just there to cope with the expansion of the coolant when hot.

IanC

 

[ccscott49]

The header tank is just that.
A header tank should be filled up to the mark, the coolant cap on the heat exchanger has a valve in it, which allows coolant to pass to the header tank, when the coolant expands. It also has a small vacumn valve, which opens when the coolant contracts, to allow the system to be topped up by the header tank, thus stopping any air entering the system and causing airlocks and subsequent "hot spot" overheating.
So the "engineer" at your yard is basically wrong.

 

[NormanS]

Leave the cap on the heat exchanger severely alone, and fill the system to the mark on the plastic header tank. End of story.

 

[wotayottie]

Provided there is always, both hot and cold, some liquid in the header tank, the level doesnt matter that much. The heat exchanger should be full at all times. So leave the cap on the header tank, remove it from the heat exchanger and then fill the latter. Replace cap (all this done whilst cold) and fill the header tank to the mark on it. Run the engine tioll hot and the header tank will most likely adjust itself by spitting out any excess. If the level in the header tank drops to nil when warm, then let the engine cool and go through the whole procedure again making a suitablke adjustment to the header tank level.

The only way this could affect engine running temp would be if there wasnt enough water in the system - too much wouldnt make any difference so your engineer is talking nonsense. Look elsewhere for the problem.

 

[lw395]

What's this 'river plate'? I can't find any description of it.
Is it possible you have an air lock in the calorifier circuit? Does the hot water get very hot as the engine approaches 95degC? Was the engine working quite hard to do this?
What others have said about expansion tank level is correct, but be aware that some manuals refer to the top of the heat exchanger as the 'header tank' as there is a reserve of water here which is above the level of the saltwater tubes.

 

[alan_d]

[ QUOTE ]
What's this 'river plate'?

[/ QUOTE ]

It's in South America, isn't it?

 

[ianc1200]

The "river plate" or as Nanni/Peachments desribe it, the "cold running kit", is for engines which don't heat the calorifier up when running river speeds. My engine is a 5.280HE, a non turbo, 62 hp 5 cylinder engine now out of production. There are some fleets of hire boats which use the same engine and had this problem, hence the kit which seems to blank off part of the raw water circulation in the thermostat housing.
It worked fine at end of last season, will top up to the mark the header tank when I return at the weekend.
The problem is that the temperature slowly rises, could well be an air lock.
Thanks for the replies, really appreciated, as I'm (hopefully) away for the week it might be a while before I can confirm, hopefully, the problem is resolved.

regards

IanC

 

[ianc1200]

Unexpectedly managed to get a hour to look at it this afternoon, unfortunely ensuring header tank filled to the mark didn't resolve the problem. Back to the drawing board, or in this case, get the Nanni engineer to look at it.

regards

IanC