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Engine overheating


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Evening all

after some thoughts of where to head with a problem we are having. 
this morning, we pulled away from our overnight mooring at tick over past moored boats. After 5 minutes, the engine overheating light/buzzer come on. 
we paused to sort out drinking water and toilet and turned off the engine. 
after 10 mins, we decided to try the engine again to pull away from the service point. The buzzer didn’t restart, we left it running for 15 mins without issue, so carried on our way. 
stopping for lunch and some shopping, when restarting, the same symptoms, warning buzzer after a few minutes, turn off the engine and wait 10 mins then it ran fine. 
 

we’ve been out for a week working round the four counties ring without any other issue. 
 

engine water level was fine on the daily check.

 

There is water in the bilge, but it looks canal water dripping through the stern tube. 
 

We were having this issue before, I changed the thermostat and flushed the engine block through with fresh water. The problem went away. 
 

Any suggestions of what might be the next item for testing?

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Fair question. 
before I replaced the thermostat, the time it happened, we had steam coming from the engine. 
another symptom was that the pipes to the calorifier and skin tank were not hot

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Perhaps an airlock in the system? Assuming there is a header tank, run the engine with the cap off and observe, see if any air bubbles come out, and if the water level drops, refill the tank. Keep checking the various hoses for temperature, check any skin tank to see if it is hot at one end, cooler at the other, and if it has a bleed screw, loosen it and see if any air comes out.

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14 hours ago, AlanJ said:

Fair question. 
before I replaced the thermostat, the time it happened, we had steam coming from the engine. 
another symptom was that the pipes to the calorifier and skin tank were not hot

Almost certainly an air lock.  But the cause may be a failing head gasket letting gas into the cooling system. 

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It happened again this morning. Cleared itself before we could clear the lock and get to the bank. Engine had been running about 10 mins.  We continued for another 5 hours without the alarm sounding. 
fan belts all seem fine. 
 

will try running without the cap on the header tank and see what happens. Obviously not cruising when I do it!

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12 minutes ago, Tony Brooks said:

I would lay odds it's the thermal transmitter for the gauge. Electrical gauge transmitters are not very reliable.

Do not think he has a gauge.  There has been no mention of a temp reading. Think the overheat switch drives a light and the buzzer

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4 minutes ago, Tonka said:

Do not think he has a gauge.  There has been no mention of a temp reading. Think the overheat switch drives a light and the buzzer

 

Less likely then, but still a distinct possibility. It's so intermittent, I can't see a head gasket being the front-runner. I think I would try to source an automotive switch that is set to between 90 & 99C with the same thread. That way would be the cheapest.

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I don’t have a temp gauge, just a buzzer/light. 
the sender on the thermostat housing has two spades on the back of it. One is connected to the control panel, the other is not connected, so I could buy and attach a gauge to it (have been thinking about this if anyone has a recommendation for a garage for a beta 38)


 

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13 minutes ago, AlanJ said:

I don’t have a temp gauge, just a buzzer/light. 
the sender on the thermostat housing has two spades on the back of it. One is connected to the control panel, the other is not connected, so I could buy and attach a gauge to it (have been thinking about this if anyone has a recommendation for a garage for a beta 38)


 

may have to call Beta Marine as they may know what gauge will match the sender. Where the sender is do you have a wire not connected which would go to the gauge or would you have to loom a wire in 

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22 minutes ago, Tonka said:

may have to call Beta Marine as they may know what gauge will match the sender. Where the sender is do you have a wire not connected which would go to the gauge or would you have to loom a wire in 

I would need to add the wire through to the gauge

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On 31/07/2021 at 21:30, Tracy D'arth said:

How old is the boat?

Make and model of engine?

Skin tank cooling?  or    Is it fresh water cooled with a mud box?    

Bled all the air from skin tank and engine?

 

 

Sorry, missed this when viewing on my phone 
 

Boat is about 30 years old.
Engine is a Beta 38 - not sure of age
skin tank which normally does get warm.
I thought all air was out of the system

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9 hours ago, AlanJ said:

Sorry, missed this when viewing on my phone 
 

Boat is about 30 years old.
Engine is a Beta 38 - not sure of age
skin tank which normally does get warm.
I thought all air was out of the system

My 27 year old Beta Tug engine had a Datcon temp guage which I had to replace due to the sender/gauge overloading recently. I could of got a sender from Beta but it was cheaper to get a gauge and sender from Asap Supplies.

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Before going to the expense of buying a gauge or a Beta overheat switch I think the  OP needs to prove if this is true overheat or simply a false reading. I would suggest a cheap infrared thermometer pointed at the thermostat housing/head may be a good first step. Only then, if it is a false reading, consider buying a new sender or fitting a gauge.

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1 minute ago, Tracy D'arth said:

 

This is most relevant.  There is no circulation.

 

That is true, but it was before the OP replaced the thermostat. It's been to have been intermittent since then, sometimes running for hours with no problem.

 

Why it overheated originally we don't know, but do know (steam) it was a true overheat. No mention of steam since then.

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I'd fit a gauge dial. Not a fan of warning lights being the first indicator of a problem. A gauge can show a normal running condition for the engine, and the heat range relative to the engine use. It's an aid, and could help to alert to erratic behaviour and faults happening in the system.  

 

 

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28 minutes ago, Tracy D'arth said:

If the stat had failed closed the calorifier would still have been hot. Replacing the stat may have just let the  engine vent.

 

True, but I suspect the original problem may well have been a lack of coolant or a big airlock.

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Morning
Thanks for the additional comments.
I did replace the thermostat after the "steam" incident.
I tested the new stat before putting in to ensure it worked correctly
I also tested the old one that I took out and it worked correctly, it was not "sticky"

I haven't had steam since - more because we stopped the engine before getting to that point.

 

I am happy to add a gauge as Higgs says, a buzzer tells me when it is going wrong, a gauge will allow seeing the problem develop.

 

When the buzzer when, the pipes to the calorifier and skin tanks were relatively cold (could easily be held)
On restarting the engine and when the buzzer did not sound, these pipes quickly got too hot to hold. 

 

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I don't have lights or buzzers, just a gauge which you have to watch. Earlier this year, said gauge went very high. I have raw water cooling and no cauliflower, and when lifting deck boards, there was no steam and all seemed normal. I changed the thermostat just in case (I carry a spare), but gauge still went high. I was able to check that the engine water pump and raw waterpump was was working by feeling the outlet from Bowman was cool. Changed the sensor and all ok.

I think there must bean airlock somewhereif skin tanks and calorifier feeds are cool.

  • Greenie 1
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