air lock in calorifier

[ste7ve]

I have a Beneteau 311 with a Volvo 2020 engine. It has a calorifier for hot water heated from the engine freshwater cooling system.
I recently changed the engine coolant and now the coolant water is not flowing into the calorifier so I have no hot water. Therefore I assume there is an airlock in the pipes to/from the engine.
There is drain cock in one of the pipes installed at a level so it is higher than the calorifier. I opened it up hoping it would allow coolant to run thru and eliminate the air lock but some water came out and then it stopped.
Any ideas on how to sort this out?

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[AndrewB]

The engine pump should easily push coolant through any air-lock in the lines. Is there any sign of engine overheating? If so my guess is a failed pump or a heat exchanger blockage. Otherwise a blockage in the calorifier or the lines leading to it.

Presumably the calorifier is correctly full of water?

 

[snowleopard]

agree with andrewb. the term 'air lock' is much misunderstood. in this case the water pump pushes coolant through the calorifier so air will be expelled. try disconnecting the pipes to the calorifier and blowing through them.

a sophisticated system on a fresh-water cooled engine will have a thermostatic valve in the feed line to the calorifier, this may be stuck or full of gunge.

on a raw-water cooled system the engine thermostat may not be opening, in which case the engine will boil.

if you have just briefly test-run the engine you may need to let it warm up before anything happens.

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[TonyBrooks]

1. Locate where the return from the calorifier return to the engine circuit. This is usually near the engine water pump inlet - not sure about your engine though.

2. Loosen clip at this point and make sure the hose will pull off.

3. Start engine and and set to high revs.

4. Pull off hose and put thumb over the inlet to the engien - leave the hose end free.

5. Water should pour out, if it does not top up engine & rev higher. Once a steady stream of water is comming out replace hose.

6. Tighten hose & top up coolant.

I have seen many "odd" calorifier instalations, but for maximum reliability (but possibly giving a slower warm up) you need the calorifier feed hose from the head and return to just before teh water pump. This ensures teh closed thermostat forces the engine water pump to push water through the calorifier.

I have never been very sucessfull with calorifiers on direct cooled boats without extensive modification to castings etc.

Direct cooled boats, modified for keel/tank cooling can be sucesfull if the full cooling circuit is directed through the calorifier, but do not choose one with a 15mm coil.

Tony Brooks


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[ste7ve]

It was all working OK before I changed the engine coolant. However there were plenty of blackish bits in the old coolant which may have blocked up something.

Yes, the calorifier is full of water, it is definetly that engine coolant is not getting to the calorifier

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[ste7ve]

i'll give it a go when I 'm next on the boat.
The only problem is I'm not sure how to identify the difference between the flow and return pipes coming from the engine.

Thanks

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[AndrewB]

And presumably the engine is not overheating so it can't be the pump or a problem with the coolant being dumped at a loose connection. Those black bits did make me think of mangled rubber impellor blades, but I don't think your engine uses that type of pump on the coolant side.

If this happened to me, at this stage I'd undo the line into the calorifier, hold the end above the level of the engine coolant header tank (you might conveniently use a short length of open hose if the lines aren't flexible enough), engage the starter and check that coolant is being pumped through. If so, undo the exit line and try blowing through the calorifier to test internally that its free. This will check if the problem is one of circulation, and whether its in the lines, or in the calorifier itself. (You've eliminated the engine already if there is no over-heating). Obviously as very hot water can be involved, you'll take the appropriate precautions to avoid scalding yourself while doing this.

 

[chrisc]

had same problem with same set up ,well similar Volvo 2030,
when I added calorifier ,problem seems to be the inlet and outlet are so high on
the engine block .
I did the simplest thing took the outlet off and Sucked the water through ,and then jammed the pipe back quick ,it has worked ever since no problem.3 years
Good for the lungs but you do get a mouthfull of antifreeze .
I can not understand why they put both inlet and outlet in this ,high ,position.

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