nearly new volvo d1-20 overheating

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laurafulcher

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This engine is about 5 years old. It was laid up for 2 years after being installed and I have used it for 2 years with no trouble except I couldn't go higher than 20,000 revs without it overheating. But that was generally ok.
This year , after a spring overhaul which included pulling a lot of disintegrated impeller out of the heat exchanger, ( another story) it is overheating after 5 minutes running at about 18,000 revs and the alarm goes off.
(The first time I investigated this I found I had no thermostat in place so I put one in but it has made no difference. ) The heat exchanger feels pretty hot. There is lots of salt water coming out the back of the boat but the coolant feels not v hot at all. Despite this it is leaking out of the filler cap on the reservoir tank and the coolant tank looks very full.
I have read a few posts on various sites and am wondering if it is possible that there is a blockage in the coolant system... But it is a nearly new engine...
any suggestions gratefully received -thanks.
 
I think you mean 2000 revs.

Is the coolant level going up as you run the engine.?The expansion tank (I assume that this is what you mean by the coolant tank) should usually be around half full when the engine is cold but will go up slightly when the engine is hot. Is the expansion tank is getting fuller as well as coolant leaking out of the filler cap on top of the engine when the coolant is still cool enough to put your finger in it?

Are you sure that the thermostat is the correct temperature range?

There could be a blockage somewhere but some more information would be helpful.

Richard
 
Sounds like the problem is in the freshwater circuit if there is plenty of seawater coming out and it is cool. However, first thing I would do is change the temperature sender as that may be defective.
 
I think that you have an air lock in the coolant circuit i.e. the cooling water that has antifreeze in it and the header tanks rather than the salt water circuit. In removing (and replacing) the thermostat air has got in and is creating a blockage and stopping the flow of the coolant water. Drain the coolant circuit and refil from the lowest point you can get to and fill it upwards sqeezing hoses as you fill. Then fill the tank on the engine and then the header tank and adjust to correct levels.
In case you're not aware, the cooling system has 2 circuits. The fresh water cooling circuit which should have antifreeze in it and this cools the engine. The second circuit is salt water whose job it is to cool the hot engine water. The heat exchanger acts the same way as a car radiator but instead of air cooling it, salt water cools it.
Hope this helps
Mike
(I've a D1 30)
 
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Just checked the workshop manual for the D1-20, and you have the same cast exhaust elbow as my md2020.
These are notorious for coking up inside and you have the same symptoms with the water leaking out the expansion tank
Suggest that you take it off & clean it out as I have to do mine every year.
It sounds like it has never been done so get a new exhaust gasket too
Also agree with the other posts about your cooling system.
 
thanks for all these helpful suggestions. It may be some time before I work through them all as I am not in the happy position of retirement and haven't much time for getting onto the boat again for a few weeks.. So I will try all these things out and report back. I agree it must be the freshwater system ( what I was calling coolant for shorthand) and I was trying to avoid pulling all the pipes off. It is such a new engine
they are all painted on and not used to being removed!
I assumed that the thermostat was in the salt water system- so removal wouldn't create airlocks. could it be that the thermostat plate wasn't sealed well enough when I screwed it back on again?. Would it be that simple???
 
No, if the thermostat cover wasn't fitted correctly then water would/will be bubbling out of it when the engine is running. The fresh water system is under pressure when hot. I don't know the exact working engine temperature but it will be very close to 100 degrees C so if there's any weekness in connections, joints and covers etc the coolant will spurt out.
Thank you Alergy, I didn't know about the coking up of the exhaust elbow. My engine has done 4 hours short of 1000 so I think I'd better get checking!
Mike
 
Vegable said:
No, if the thermostat cover wasn't fitted correctly then water would/will be bubbling out of it when the engine is running. The fresh water system is under pressure when hot. I don't know the exact working engine temperature but it will be very close to 100 degrees C so if there's any weekness in connections, joints and covers etc the coolant will spurt out.
Thank you Alergy, I didn't know about the coking up of the exhaust elbow. My engine has done 4 hours short of 1000 so I think I'd better get checking!
Mike
Click to expand...

I would check it , I take mine off each year and clean it and you be suprise would it like each time .
My D2 40 is now in its seven year and I had to replace it last year with an SS one the Volvo one corroded.
 
Has the engine burped at all..

What I mean by that is when a fresh water system is filled from empty it has lots of air in it. The thermostat will be closed as it's cold. The engine is run up..gets to temp and the as the thermostat opens it burps...the air in the closed fresh water system is forced out and it takes water in form the overflow tank. This is how almost all modern engines work when first filled up.

The lack of a thermostat will make your engine run cold not hot so that is not the cause..but it will cause your system to struggle to run up to pressure from cold and to expel any air in it.

From what I can tell it really does sound like air in the fresh water cooling system.

Check the water in the overflow tank...take the lid of the tank...get the engine to temp...when the thermostat opens you should hear the burp through the overflow tank.
 
Sailorsam101 said:
Has the engine burped at all..

What I mean by that is when a fresh water system is filled from empty it has lots of air in it. The thermostat will be closed as it's cold. The engine is run up..gets to temp and the as the thermostat opens it burps...the air in the closed fresh water system is forced out and it takes water in form the overflow tank. This is how almost all modern engines work when first filled up.

The lack of a thermostat will make your engine run cold not hot so that is not the cause..but it will cause your system to struggle to run up to pressure from cold and to expel any air in it.

From what I can tell it really does sound like air in the fresh water cooling system.

Check the water in the overflow tank...take the lid of the tank...get the engine to temp...when the thermostat opens you should hear the burp through the overflow tank.
Click to expand...
 
Thank you for all your advice. I realise that I had done most of the things on the list and I decided to enlist the help of my local engineer. He spent an hour running the engine and suggested that I get a new cap for the freshwater reservoir ( header tank), as the old one leaked. So I spent about a tenner on this and hey presto- no more overheating! There is some sort of valve inside the cap that presumably adjusts the pressure of the freshwater coolant. But it worked!! It seems a bit basic and I don't understand why, but they say it's always the simplest solution. I will get down and decoke that elbow in the winter though...
 
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