Calorifier problem

[Meps1983]

I filled up the water tank yesterday after the winter layup. Ran taps till they had no air coming from them in both the galley and the heads as I do every year. A few hours cruising, and I'm just getting cold out the hot tap.
I opened the pressure release valve, and that was also cold. The hoses going in and out from the engine were both warm to touch but still only cold from the hot tap. It was all working fine at the end of the season so I assume it's an air pocket? Any ideas or tips would be great.
Thanks

 

[PCUK]

Slacken one of the connections from the engine to the calorifier and that should release any trapped air.

 

[Meps1983]

I did think about that but both the inlet and outlet pipes are warm? I think the issue is probably the fresh water side as opposed to the coolant loop. I could be completely wrong of course

 

[PCUK]

If it's the fresh water side then the calorifier must be empty and obviously it's not.

 

[Meps1983]

That makes sense now i think about it! Is it possible that the airlock is in the on the engine side then? My engine is freshwater cooled so could that get air in the system even though I've not drained it in anyway?
Thanks

 

[Plum]

I did think about that but both the inlet and outlet pipes are warm? I think the issue is probably the fresh water side as opposed to the coolant loop. I could be completely wrong of course

I also suspect an airlock in the engine/coolant circuit. I used to get this a lot. There would still be a little flow, so the hoses did feel warm/hot. The airlock would form over time, even if the coolant had not been drained. I used to have a bleed valve at the highest point of the hoses to/from the calorifier. Eventually I got round to re-positioning the hose runs so there was minimal rise and fall so no longer get an airlock. If this is what is happening to you then should be straightforward to fix.

 

[PCUK]

Back to square one and my first suggestion.

 

[Boaty_Pete]

On some engines, (mine and a few I've worked on) there is a valve in the outflow or return, or both for the calorifier.
One year it had been rotated to nearly closed (round top, not lever style.)
It caused us the same issue.
We were convinced none of us had touched it, but that was it.
If you have an airlock or a restriction of some sort the pipe will be warm or hot, but not shift enough water to heat the tank.

 

[Meps1983]

I'm back over to the boat in the week. So I'll have a go at cracking the hose from the engine to the calorifier. Am I right in thinking the engine will need to be up to temp before I losen the hose?
I'm pretty certain there's no bleed valves along the lines so that would be a good idea to perhaps add one Plum.
Thanks again for your time.

 

[Plum]

I'm back over to the boat in the week. So I'll have a go at cracking the hose from the engine to the calorifier. Am I right in thinking the engine will need to be up to temp before I losen the hose?
I'm pretty certain there's no bleed valves along the lines so that would be a good idea to perhaps add one Plum.
Thanks again for your time.

Suggest you do not loosen the hose when up to temperature as it will also be under pressure! Anyway, may not solve the problem. If there is an airlock it will be where one of the hoses to/from the calorifier goes up then down again so trapping the air in the high part. Very very unlikely there is trapped air where the hoses connect to the engine.

 

[PCUK]

Groan, The only way to vent is to loosen the hoses. Do it at the weekend on a cold engine.