No hot water

[ColinS]

Due to starting problems on my Volvo 2002 I did a top end rebuild over the winter and honed the bores at the same time. There was the usual scale and suchlike around the waterways, which I removed carefully, because it seemed the thing to do.
The engine now starts within 2 seconds from cold (rather than using easy-start as before) and I am most pleased with the result.
However, I now find that there is very little water flow through the thermostat when the engine is up to temperature, and consequentially I have no hot water from my calorifier. This time last year I had no problem getting hot water, and so it is not due to the sea temperature.
I have removed and tested the thermostat, checked all of the calorifier pipes and run with them disconnected and emptying into a bucket, with the result of a very slow trickle of water. I have also checked the water pump impeller as well.
I would presume that the bypass flow into the wet exhaust is taking all of the water supply from the engine with the result that there is no flow through the thermostat, so is there a way to reduce the bypass flow or should I wait for the scale to build up again?

 

[Ceejay]

Air lock?
CJ

 

[sarabande]

was the calorifier flow check done before or after the unit ? i.e. if after, could there be an obstruction in the unit itself, say by the pressure relief valve ?

 

[ColinS]

I removed the pipes at the engine and calorifier and blew through them to make sure there were no obstructions, and then re-fitted the engine end of the feed pipe (from the thermostat). The return end at the engine was blocked off for the test to stop blowback of exhaust fumes and water (which I found out about previously).
As I said, there is a trickle of water coming through, but not enough to even think of warming the tank, although I got a small surge of water for a second or so when the throttle was closed and the engine revs dropped.

 

[RAI]

Try again a couple of times. I had the same problem but it solved itself after a couple of thermal cycles (engine cold to hot).

You could try pre-filling the calorifier circuit with a funnel to get most of the air out.

 

[tt65]

I lost hot water last year on my Bukh. It turned out to be the small pump that pushes the hot engine water through the calorifier that was not working. A small amount of debris was stopping it. Does Volvo have anything similar. I did not know mine was there until after it failed.