Engine overcooling - and undercooling

[Col]

I agree with all the above suggestions, just 3 things to check

1/ circulation pump- I have seen these on several engines where the impeller is slipping on the shaft ( At low speed it can cope, but the higher the revs, the more the load on the pump so it slips ) bit like a duff clutch on your car !

2/ T/stat -see all previous postings.

3/ Exhaust can be partially blocked. Run it at high revs till the gauge starts to rise, should have plenty of cool water exiting exaust outlet, If flow is hot/reduced check for blockages. Also check if water hoses are " ballooning " sea water needs to get out as well as in.
Best of luck !
let us know what you find.

 

[gunnarsilins]

To everyone assisting me.....

I wont mention any names, but nobody is forgotten either!

Thanks alot all of you for taking your time and effort. Just a few hours - and I had so much valuable information so I can spend the rest of the winter in the engine room!

Just a few comments to the last contrubutors;

*No, this problem is not associated with growth on the bottom.

*I have throughfully checked/rebuilt the whole raw water system - from seacock, through the engine and the axhaust sytem as well. And airleaks....no every joint is redone.

*Blown head gasket would show up on a compression test, wouldn´t it?

The action I´ll take from now is (in more or less order)

*Check the thermostate again. I changed it once because it was the first item I suspected when I bought the yacht. But it might stick, for some reason, maybe the gasket is doing some tricks.....
See what happens when running without one

*Check the oil temperature to see what happens there.

I´ll let you know - by spring probably!

Thanks again!

Gunnar

 

[charles_reed]

Good luck nm

nm

 

[LadyInBed]

Re: 1/ circulation pump

1/ circulation pump

Along these lines, if the engine has done it since adding the calorifier maybe the circulation pump cant raise the pressure required at higher revs to push the volume of water around the system to keep the temperature down.

A water pressure gauge or maybe a flow meter would tell you this.

 

[gus]

Re: Another suggestion!

Consider also the possibility that for some reason your injection timing has slipped. Also check that your injectors are functioning correctly - are they fouled perhaps. It is a very good idea to fit an exhaust manifold temperature gauge as it lets you know constantly the condition of your combustion process within the engine.

 

[jfkal]

Was the problem always there? Did it develop over time or came on suddenly??
Since you are in cold waters the undercooling could happen if the thermostate does not close completely (it do that by design...). Overheating seems to be due to insufficient water flow. Check water in and out temperatures independently for both the fresh and sea water circuits. If the sea water outlet seems to be cool your problem is in the primary circuit. (Did you check all impellers for wear and tear?)