Is my circulation pump faulty?

[oddynoki]

I recently stopped getting any hot water on my boat (Stirling Sabre 29 with Volvo Penta AQ140A)
The hot water tank/heat exchanger is connected to the engine cooling system (the part with antifreeze, not the raw water part)
I am worried that the reason for no hot water is the circulation pump is broken, and the more I run the engine the more damage I will be doing.
According to the temp gauge the engine is not overheating.
Could there be any other reason for no hot water?

 

[iangrant]

Air Lock?

Is there any water in the HW tank, is the coolant header tank topped up?

Does water flow albeit cold?

Ian

 

[Bilgediver]

Could there be any other reason for no hot water?

It is not unusual for calorifiers to airlock and some can be difficult to get rid of the air especially if they are higher than the engine.

Feel your hoses with the engine working. The hoses in the engine could all be about the same temprature indicating engine cooling is fine however you may find the hoses in the calorifier circuit are cool indicating no circulation.

Is there a closed valve in the calorifier circuit. (calorifier=water heater)

 

[PCUK]

Circulation pumps are so simple - a rotor pushing the water round - that the only thing to go wrong is the seal which can leak.
Problem lies elsewhere probably as discussed above.

 

[oddynoki]

Thanks for your replies.

There must be water in the HW tank as water flows from the tap albeit cold.
The coolant header tank is topped up. I did have to top it up with about half mug of coolant a couple of weeks ago but hasnt gone down since then (engine ran for a couple of hours)

The pipes that run from the engine to the calorifier are cold, and also can be squeezed, I would expect them to be more solid if water was running through it?

There is what looks like a inline valve near the HW tank.

I'm hoping its a air lock as you say, any suggestions on how to remove it?

Cheers
Dave

 

[PCUK]

Disconnect the return to the engine and suck! Maybe using an outboard motor priming bulb or some such thing. Mouth as last resort due to anti-freeze killing you!

 

[andy59]

An air lock will naturally go to high point in system so if you can , undo highest pipe joint ( engine cold and header tank cap still on ) and squeeze any of the largerubber tubes on cooling system , if water comes out connect pipe back up before letting go off squeezed pipe ,( may need 2 people ) . you may have to introduce an air vent to system if the problem keeps hapening , depends on pipe layout . In an ideal world everything should be below header tank .

 

[1973keith]

"There must be water in the HW tank as water flows from the tap albeit cold."

Doesn't necessarily mean there's hot water in the heating coil in the tank though...

"The pipes that run from the engine to the calorifier are cold, and also can be squeezed, I would expect them to be more solid if water was running through it?"

The fact the pipes are cold is weird, and they should be firm if the closed circuit water is getting hot...

There is either no water in them, could be an airlock as mentioned before,
the coil in the tank could be blocked with sludge, or your thermostat could be stuck wide open stopping the whole engine heating up properly.

Is the block getting hot?

 

[Bilgediver]

Thanks for your replies.

There must be water in the HW tank as water flows from the tap albeit cold.
The coolant header tank is topped up. I did have to top it up with about half mug of coolant a couple of weeks ago but hasnt gone down since then (engine ran for a couple of hours)

The pipes that run from the engine to the calorifier are cold, and also can be squeezed, I would expect them to be more solid if water was running through it?

There is what looks like a inline valve near the HW tank.

I'm hoping its a air lock as you say, any suggestions on how to remove it?

Cheers
Dave

The best way to remove the air lock is to run the engine to heat the system then stop the engine when it is pressurised and slacken of a joint or jubilee clip at the highest point and let the air out. You might need to do this several times.

Is the valve you mention which is in the heating coil circuit actually OPEN?

 

[oddynoki]

Problem solved

It took a while but Ive finally fixed this problem.
Where the pipe from the calorifier joins the engine block (not sure wether its
the inlet or outlet), there was a blockage. I put a screwdriver into the hole and met resistance so pushed a bit harder and freed up whatever was blocking it, probably rust? and it works fine now.
I'm a bit worried though, having run the engine a few times with this blockage
that there was no circulation so it may have been overheating and caused some damage? The temperature gauge didnt show any overheating but surely it must have got hot?
Thanks again for all your replies.

 

[PaulGooch]

A blockage in the calorifier circuit won't cause the engine to overheat. Do make sure that you have the correct strength of anti freeze in the coolant though. This will help prevent corrosion in the cooling system.

 

[nedmin]

In most sysems it doesnt matter to the engine if the feed to the calorifier gets blocked as its entirely separate to the engine.Its usual for the feed and return to the cal to have stopcocks fitted so that you can remove the cal .You could still use the engine with these stopcocks closed.Might be worth while flushing your engine cooling system out as if the cal pipes got blocked the foreign body is coming from somewhere.

 

[Dave_Seager]

If the calorifier is not fitted then there would be blanking plugs in the engine where the hoses connect anyway.