Volvo Penta 2002 - Overheating

[blueandy_a]

Hi
I have a problem with my engine. Its a volvo 2002 (1991) fitted to a Westerly Merlin. I removed the heat exchanger to fix a salt water leak at the rear plate. Reassembled and fitted the heat exchanger taking care to align the rubber gaskets. After starting the engine and running for 30 mins or so, the engine warning siren came on along with the engine oil warning light. There is plenty oil in the engine, no oil leaks and no burning oil coming out of the exhaust.
I think the problem may be the fresh water coolant temperature as the thermostat housing is really hot as is the pipe from there into the heat exchanger; however the fresh water outlet pipe from the heat exchanger is really cool suggesting the fresh water is not circulating.
The sea water system is fine and running into and out of the heat exchanger and out of the exhaust. I removed the heat exchanger again and all the water runs free through it on both fresh and salt water.
There is a calorifier fitted - could this be airlocked and cause a lack of circulation and if so how would it be bled? The other part i'm going to check is the thermostat and lastly the water pump.
If you can give any advice I would be very grateful.

Thanks
Andy

 

[MoodySabre]

There was a post some time ago about heat exchangers which I was interested in here . I don't know if this will help you be certain that you have put it back together again properly.

 

[dawnsall]

Hi I have a 2003T and when draining the cooling system I have in the past got an air lock in the calorifier which produces the symptoms you describe. I use a dingy pump on deflate to suck the water through the calorifier it all ways gets a bit messy but works. I also take my time in filling the system. Good luck.

 

[blueandy_a]

Thanks to both for a very quick reply. I will take on your advice and go back aboard tonight and see where it takes me.

Regards

Andy

 

[Jabberwock]

You might also check the screw in fitting to the thermostat housing which connects to a pipe to the expansion tank. The small orifice in it can easily block with debris. This causes an air lock in the cylinder head cooling and a (genuine) overheat warning. As you say the heat exchanger stays cool

 

[marina95]

You might also check the screw in fitting to the thermostat housing which connects to a pipe to the expansion tank. The small orifice in it can easily block with debris. This causes an air lock in the cylinder head cooling and a (genuine) overheat warning. As you say the heat exchanger stays cool

Replying to this old thread - just to say that Jabberwock's response above was the solution to our issue. So, if you're getting raw cooling through the engine but the heat exchanger is not getting hot (and you get an overheat alarm), then this is a good place to begin. We'd spent a good few hours trying to work out what was happening and were on the verge of taking the thermostat out for inspection when we found this thread. 5 minutes work with a needle and all was good. Thanks Jabberwock.