Engine overheat alarm on Volvo engine SO32

[rodgerg]

Can anyone please give me an answer to whether the above alarm is connected to the radiator/heat exchanger or the exhaust? While motoring to Bute in the teeth of a Force 6-7 my alarm went off. I switched off turned around hoisted sail and then went to investigate. A little green water/ anti freeze had been discharged, only about a quarter of a cup. I waited until the engine cooled and I was surprised to find the radiator still full. Just before the alarm I had looked overside and I was discharging the correct amount of water with exhaust. A short while later I restarted engine and she took us back to home Port. The strainer was clear apart from a few of those little prawn things that seem to also get into the log. I am at a loss!

[electricmonk]

Unless it has been modified the temperature sensor is connected to the engine around the thermostat area, not the exhaust.

As far as I know the same alarm sounds for low oil pressure, high temperature and on some I've seen no alternator output. I would check oil level, battery acid level, drive belt tension and the coolant levels you have checked.

OR MAYBE the engine panel got wet when you were punching into the weather and that set it off, again as far as I know the control panels are not water proof.

[rodgerg]

Thanks Electicmonk however it was without a doubt an overheat alarm. My board has individual indicators and this was a thermometer. I have two brand new batteries anyway. So far I have checked my main inlet for obstructions, checked the impeller which is ok. I have also had the heat exchanger out and it was totally clean no debris at all. I traced the sensor and it is adjacent to the block so its the engine temp it was sensing. I will take her out over the weekend and test her out to re-assure myself before our summer trip next month. Still unsure why the heck it went off though.

[benboon]

Dear Rodger,

You may already have solved your problem, but I would like to share my experience.
I've been through the same situation two (or three?) times in similar conditions. This happened the first time I used the boat after purchase 3 years ago.
We did the same, clean inlet (was slightly blocked first time), replace impeller, even replaced water pump house but all to no avail.
My final conclusion was that the engine overloads in these conditions. I hope I have solved it by fitting a folding propellor (Helice 2-blade).
It has not happened since, but I must admit that I try not to go full power in heavy wind situations. You could also consider to have your propellor pitch reduced, but this is something to review with a specialist.
I understand there is also an option to fit a small overflow tank that could also solve this issue.

[sailbleu]

benboon,

have you checked the exhaust elbow ?
After some time they get clogged up resulting in less secundaire waterrflow, resulting in overheating.
This vital part should be checked every so many years.But it can also be noticed by a reduced water outflow.
Which was the case in my case.

Regards

[JEF]

Rodgerg

The engine undoubtedly overheated when under high load only ... 

Fully check out the fresh and raw water systems to ensure full unrestricted flow ... it seems you have checked the obvious on the freshwater side however I would also recommend the following jobs ..

Remove the exhaust elbow to ensure no restrictions in raw water exit areas this has been a know issue on older engines.
Remove the thermostat and test for check opening correctly , unrestricted.... the opening temp is normally marked on stat body.
Remove the fresh water coolant and flush out engine with a flushing agent easily obtainable.
Refill the engine coolant with fresh correct antifreeze to water mixture ... refer to your operation manual if unsure or ask your local Volvo agent for recommendation. The mixture should be changed every three years if I remember correctly
Check the heat exchanger filler pressure cap to ensure it is good condition and seating correctly

For pre passage reassurance ..Test engine under extended full load at dock side if at all possible. 

 
I am a previous owner of SO32 and a qualified marine engineer , Hope this helps solve the problem

[ianqv]

Hi Goldfinch

You have had some great suggestions on possible causes....

I had the same thing last year, it turned out to be the thermostat mucking around. But it didn't always stick (at first)
My advice would be carry out all of the aforementioned suggestions, but, if you are removing the thermostat refit with a new one. Of course you can check it in boiling water, but just by removing the thermostat you can "unstick" them if they are a bit "dicky" (technical term!! ).

One good way to check if it is a thermostat..... if the engine ever gets hot again, "carefully" place your hand on the top of the heat exchanger. Hot / v hot = thermostat is open. Cold, or just warm could indicate a shut thermostat (assuming everything else appears to be working... i.e she's pumping water and so on).

Now this next part will NOT suit everyone. I binned my thermostat! i.e my engine runs without one.
Thermostats are only fitted for the following reasons:
To bring the engine temp up to normal operating temp asap - this can also help emissions during warm up phase.
To maintain a normal engine temp - if you are sailing in cold climates and sucking up v cold water your thermostat may not be fully open in an attempt to keep everything warm / hot.
I sail on the East coast UK, never sail in the winter... (or when it's cold!!! )

The down side to this.... if you want to run your engine just to heat up your calorifier, you will have to wait for longer! Also if you have a modern engine governed by engine management - this may give you a fault code or even drop you into L.O.S (limited operational strategy).

If your engine did overheat also check to see if your calorifier temp cut out has been activated. If your engine got to hot, there is a chance the water in your calorifier was also v hot. If you are still getting hot water via switching it on when connected to shore power then it hasn't tripped out.
If it doesn't heat up you need to throw the trip switch back in. This can be found on the side panel of the calorier. NOTE - switch off the mains first as it is v close to the mains wiring.

Please do let us all know how you get on.

Best Regards

Ian

p.s I see you are at Levington... I'm just down the road at Bradwell

[JEF]

Will be at the East coast boat show @ shotley marina 26/27 april .... proably down to Bradwell early may drop me a line if you still need any help .

yacht .. Goldfinch
mmsi .. 235 094 224
call sign 2FTX3
yacht mobile [phone]