Volvo 2003 Overheat

[Jabberwock]

The local Volvo dealer and I are flummoxed with an overheating problem on this engine. It has been a recurrent problem and is often cured by clearing out the small orifice attached to the thermostat housing from which a pipe leads to the fresh water resevoir. Apparently if this gets blocked an air lock occurs and the cylinder head overheats.
Anyhow after sometime without a problem an overheat warning occured - so I cleared out the orifice (previously enlarged by Volvo engineer) and for good luck blew through the pipe to the resevoir.
Next time out another overheat after about 45 min at 2000 rpm so called in Volvo agent again. After inspecting thermostat etc engine run on pontoon with drive engaged at about 2400 rpm for a good period with all quite normal including temperatures stable to and from calorifier, heat exchanger, cylinder head at all 3 cylinders etc. (They had a very nifty point and read thermometer gadget)
Next time out after less than 30 minutes at about 2000rpm another darned overheat!
Please note definetely not lack of sea water cooling as healthly flow at exhaust and heat exchanger always cold. However I did notice with Volvo present and all OK centre part of heat exchanger just a touch warmer which is apparently as it should be, but on last occasion it was stone cold along its whole length.
Volvo of course ran it with the steps and hatches all removed, while these were on when in use. However at their suggestion I did inspect the two air ducts to the engine "room" (Moody Eclipse 33) and both were clear. And the boat did spend some years in Greece apparently without any problem.
The warnings are geniune because if the engine is not throttled back to idle, or shut down, quickly there is coolant loss from the header tank.
Can it be a problem that only occurs at low to moderate throttle settings?
Any suggestions?

 

[EdWingfield]

Just a thought. When I had to change a broken impellor on my 2003 an engineer said I must find any broken rubber pieces, as these could lodge themselves somewhere, causing cooling problems.

I found 'em in the exchanger.

 

[chrishelen]

If the heat exchanger is cold, or just warmish its not doing its job properly,i suggest you start at the sea water inlet and work up to the exchanger strip it down give it a good clean get rid of all the solidified salt and crud,and when its all back together see what happens.When did you last change the impellor?

 

[boatmike]

I agree almost certainly the problem. Surprised the Volvo engineer did not suggest it. Suggest you remove all external piping and check for bits lurking there and then back flush from heat exchanger with hosepipe. If you want to be totally sure, remove water pump and thermostat and make sure there aren't any bits lurking there either.

 

[Juggler7823]

You should check all the external cooling pipes and espescially the small one t the back of the engine connecting the head and the exhaust elbow.
Roy

 

[adko]

Hi,

Fairly new to the forum but I agree with chrishelen. Had a similar problem on my MD2020 - it turned out to be caused by the heat exchanger cores being surrounded by soft crud which effectively insulated the saltwater from the fresh hence no heat transfer was taking place. Just flushing the exchanger through was no good - had to completely dismantle it and clean with SWMBO's dish brush which did the trick!

Incidentally, the first sign of my overheating problem was water leaking from the escape valve of the calorifier - seems the problem was getting progressively worse over a period of about a year until the engine wouldn't run for any time at high load without overheating. Cleaning the exchanger cores solved both problems.

ADKO

 

[Bav34]

Hi ADKO. I have sent you a PM ... little flashing icony thing. Cheers Steve

 

[yotter]

Just a thought,
One difference from motoring at 2000 rpm at pontoon vs sea, is the flow rate past the coolant inlet seacock. (stopped vs 5 to 6 knots) Reasons for any difference in performance could include any sources of aeriated seawater up-stream of the seacock. This could cause bubbles in the rawwater coolant which would degrade its cooling performance. Probably rubbish but logical!

 

[Jabberwock]

Thanks for the suggestions. I take the point about the heat exchanger being crudded up. But if so why was it working perfectly with the engine being run by Volvo while moored. Also if there was any blockage or problem in the salt water circuit surely the heat exchanger would be hot not cold. And in any case there is always a very healthy flow of water out of the exhaust. I did change the impeller less than 50 hrs ago as a precaution althougth the previous one was fine.

 

[themons]

I had the same problem. Try changing the coolant to 60 water, 40 antifreeze.

 

[EdEssery]

On my direct cooled Volvo 2001 engine the water pumped from the impeller enters the block of the engine roughly in the centre and flows through a copper pipe in the block and out of the back of the block from where it feeds up to the rear of the injection elbow on the exhaust. The thermostat sits on the top of the block and opens at the appropriate temperature to let the water flow that way into the injection elbow. Where does the water that the thermostat lets past come from? It enters the block through holes in the copper pipe that runs from the front of the block to the back. The holes in this pipe get scaled up and prevent sufficient flow through the block to the thermostat.

I had this very problem on my 2001.

You can remove the pipe from the block by disconnect the pipes from the front and back of the engine and then knocking the pipe out of the block from the front to the back with a drift. There is a flange on the the end of the pipe at the back of the engine which is why it can only be inserter and removed one way. As you withdraw the pipe note the orientation of the holes (6 o'clock, 9 o'clock etc.) and ensure you replace it in the same orientation. There is also a rubber seal on the flange - it's a good idea to replace this whilst you have the pipe out as it's a major source of water leaks down the back of the engine.

A search will revela other discussions of this issue on this forum. It's how I found and solved my problem.

Hope this helps.

 

[chrishelen]

But before you do all of this please make sure the H E is clear as 9 times out of 10 in my experience its the cause of overheating.