Overheating Volvo Penta 2003

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Donheist

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I had a major overheat the other day, melting alternator belt and causing coolant to dump in bilge. Let it cool, changed Coolant, and changed belt.

now still overheating within 30 minutes of running at medium revs

raw water seems fine - plenty water from exhaust, inspected strainer and impeller - all good. Coolant no longer leaking although it’s only water - do t want to put the coolant in TIL sure all is well (hard to get rid of not that I’m cheap!). Oil is new and right level. Belt tension fine and freshwater pump spinning

so my next move is the thermostat. Sound right? Anything I’m missing?

thanks
 
Checking the thermostat is probably a sensible next move. It should just start to open at 74C and be fully open at 87C

When was the heat exchanger last cleaned? When was the seawater pump impeller actually last changed?

You might be able to get some idea of whats going on by feeling the temperature of the hoses going to/from the heat exchanger.
 
I agree with Vic.

Keep a very close eye on the oil level and whether there is any emulsion on the dipstick and a close eye on the coolant level and whether there is any sign of bubbling or over-pressurising or oil film in there. Overheating sufficient to melt the belt is serious overheating. :(

Richard
 
Is this a raw water cooled engine or heat exchanger//// Volvo did both.
If using a heat exchanger, the small pipe from the header tank can and does get blocked with Calcite. This can cause difficulties in getting the air out of the engine, If its blocked, then drill it out. But this will not be the cause, but contributory.
as already said, if its been a number of years since you inspected the heat exchanger and cleaned it through you will have to look at it. Often it only causes problems at higher revs and in slow running enough water gets through /heat produced.

Could the exhaust water injection bend be clogged up - - although you say there is good flow out the exhaust.

Check the Thermostat.... Put it in a saucepan and see at what temp it opens.

On all these engines these things are a regular maintenance item but often come under the heading of "out of site our of mind"
I cannot help but think that the belts may be the cause . Unless you have a 100 amp alternator that would not be the cause, so check that the internal water pump and alternator bearings are good. Something must have caused this burn out, and that needs answering.
 
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VicS said:
Checking the thermostat is probably a sensible next move. It should just start to open at 74C and be fully open at 87C

When was the heat exchanger last cleaned? When was the seawater pump impeller actually last changed?

You might be able to get some idea of whats going on by feeling the temperature of the hoses going to/from the heat exchanger.
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Thanks! Heat ex cleaned 2 years ago professionally. Impeller last April and inspected November. Oil clean and levels right. Threw the Previous owners massive alternator away years ago and just have a (genuine, four year old Volvo) original which is charging.

I don’t have a thermometer. Any tips for knowing temperature between too hot for hands and boiling?
 
I believe that this thermostat should open at around 80C. At 70 you can just put your fingers in, but you don't need to do that - just watch it as is warms up and if it hasn't opened by the time its boiling, its not working! Unless you are at the top of Mt Everest
 
Chris_Robb said:
I believe that this thermostat should open at around 80C. At 70 you can just put your fingers in, but you don't need to do that - just watch it as is warms up and if it hasn't opened by the time its boiling, its not working! Unless you are at the top of Mt Everest
Click to expand...
I wouldn't recommend sticking ones finger in 70 degree C water as that is seriously hot .... but the rest is spot on. :)

Richard
 
If the first belt was melted, then you changed it for a new belt and it overheated again, then when checking engine another time you noticed the belt loose, I do wonder is something starting to seize when the load of the belt is put on it and wearing away the belt. Did you notice a lot of black dust gathered around the oil filter? I would double check the alternator and fresh water pump, make sure the pulleys spin smoothly and that there is no excessive play at the pulleys.
Also, do you have a calorifier fitted? If you do you could check the temperature of the coolant pipes at the calorifier. If they are cold when the engine has heated up it would indicate a problem with coolant flow, probably a problem with the coolant pump.
 
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If it has been that hot I would check the exhaust hose for delamination
there is is a Flute like water distribution pipe that runs internally in the cyl head which has a tendency for the small hose to choke
mark the pipe so that the holes are properly aligned
 
RichardS said:
I agree with Vic.

Keep a very close eye on the oil level and whether there is any emulsion on the dipstick and a close eye on the coolant level and whether there is any sign of bubbling or over-pressurising or oil film in there. Overheating sufficient to melt the belt is serious overheating. :(

Richard
Click to expand...

Is the engine water pump seized or tight to turn? That would melt the belt. I have repaired professionaly many badly overheated car engines, not very often finding a damaged belt.

Like you, I find the melted belt bit surprising.
 
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