Volvo 2003T overheats on Idle

Happydaze said:
With overheating, its not always easy to tell if the problem is in the sealed system or the flow of water to cool the sealed system, and my earlier post referred to just the raw water system.
The sealed system does use the centrifugal type pump which relies on a close fit between the vanes and the back part of the pump to push the water around the engine and calorifier etc and it is possible, if this pump has had a repair kit fitted, that the new bearing/seal has not been pushed far enough into the housing or the solid impeller has been pushed a bit too far onto the back of the shaft, making the pump ineffective at low speed.
Click to expand...

Vic and Happy daze, thanks for your contributions. I spent ages yesterday maiking sure that every last drop of air was out of the system. I left it ticking over after we had got into Kithnos (spanking close reach) and it did not move the gauge at all. So I think it really is down to the air in the system. I will just have to keep checking it but it does not take long.

Happy Daze - the water pump is the original and the raw water size pulls through tones of water - a bucket in about 30 seconds.

Thanks all.
 
It sounds as if there are no problems on the seawater side if you get plenty flow through and it is cool at the injection point so your problem must lie with the fresh water side. Have you checked your freshwater pump drive, it may be slipping at tickover which would give just the symptoms you describe. There could be some restriction to fresh water flow which is overcome by additional flow when you speed up but at the moment I cant think of any other than perhaps a partially malfuntioning thermostat.

It may be worth taking out and checking the FW pump.
 
Problem has gone away!

I bled the water system again, allowing lots of water to come out as well. I left it idleing after berthing today for 20 minutes -- the temperature actually dropped. There was hardly any air in the system, so I cannot really understand what is going on here! Anyway the problem seems to have gone away - for the time........
 
Problem Solved - what was wrong

Chris_Robb said:
I bled the water system again, allowing lots of water to come out as well. I left it idleing after berthing today for 20 minutes -- the temperature actually dropped. There was hardly any air in the system, so I cannot really understand what is going on here! Anyway the problem seems to have gone away - for the time........
Click to expand...

I found that the return from the header tank - the thin rubber tube to the thermostat housing, was completely blocked, making it very difficult to fill up again with water. This came to light after having a seal on the heat exchanger disintegrate (20 years old) and found it impossible to get rid of airlocks to get water into the system. I took this pipe off and found the narrow hole into the head was completely blocked. I put a 6 mm drill through it, and all was solved.
 
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