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Overheating Engine (?) - where does coolant go, and what is our cooling system?


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10 minutes ago, Grebe said:

The remote analysis has been great but I'm sorry to go back to basics, but are we sure that we are not just dealing with expansion when the coolant heats up.

 

Owner fills header tank to brimming - turns engine on - coolant heats up and expands and creates pressure in the system - 'radiator cap' operates like it should and dumps the excess water.

 

 

That is entirely possible. There is a natural level and anything more will just get blown out. However the OP is talking about overheating and high temperatures on the gauge, so suspect it is more than just that. My engine has no external expansion tank and there is a definite level in the heat exchanger that it will settle at, just above the fins.

Jen

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Those convoluted hoses don't help the circulation. The turbulance those convolutions can cause to the flow are like putting lots of little brakes on. Sir Nigel Gresley of A4 steam loco fame streamlined all the engines internal water and steam piping, no sharp bends apart from the boilers superheating tubes, no obstructions, no convoluted pipes, And look how much faster it went, Mallard 126mph in 1938.

  • Greenie 1
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1 hour ago, Tony Brooks said:

FWIW. Unless you can find a pipe or hose linking the engine cooling system to the push fit plastic plumbing I am now all but sure those header tanks have nothing to do with engine cooling.

 

The exhaust manifold (the box with the "butterfly" pressure cap on it) probably acts as the coolant header tank on your engine. This is the conventional way of doing it until it was realised that with skin tanks the expanding coolant could empty the header and allow air into the skin tank. l would fill to the bottom of the filler neck. Run up to temperature and allow to cool. Coolant will be blown out of the pressure cap abut once its cool whatever coolant level then that will be the full level.

 

Fill and bleed, keep filling until  no more air/gas comes from the screw hole. then top up.

Update: the plastic box, the right one, actually does feed into the engine (as well as the calorifier). We filled it up with coolant and we are now running the engine before we let it cool and bleed the skin tank.

 

Someone else asked if coolant is just spluttering because we keep overfilling it. We haven't filled it before, and it didn't splutter in the previous three months that we've had the boat.

 

On whether we have tried it whilst moving, not yet. I figure that bleeding the skin tank is good to do anyway, and if that doesn't cure it then perhaps it's just where our boat is positioned.

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10 minutes ago, Thomas C King said:

Update: the plastic box, the right one, actually does feed into the engine (as well as the calorifier). We filled it up with coolant and we are now running the engine before we let it cool and bleed the skin tank.

 

 

If it really does feed into the cooling system then it won't also feed into the domestic water part of the calorifier. However it may well feed into or out of one of the coils close to the calorifier. My guess would be to a high point so it vents any air from the coils.

 

If the brass fitting on the little pipe in the filler neck on the engine is a blanking plug then the cap on that filler shoudl either be a solid one with no springs or a  higher pressure  than the one on the plastic expansion tank.

 

Filling via the plastic tank may well leave a lot of air in the manifold heater tank. I would fill the manifold first then put the cap on and put about an inch of coolant into the plastic tank.  Remember that once you are sure the problem has gone you will probably have to refill the system with a 30% to 50% antifreeze  mixture.

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28 minutes ago, Tracy D'arth said:

50% antifreeze is the minimum concentration for continued corrosion protection.

TD'

 

We will disagree on that. 50% is the usually recommended maximum concentration because if you go higher the coolant looses its ability to carry as much heat away. Typically 33% is recommended by the manufacturers.

 

I find antifreeze tends to be very searching so if you g to high you find little weeps in the system.

 

The corrosion protection is done by sticking to the manufacturer's coolant change intervals and that could be anything from 2 to 10 years or more depending upon the antifreeze & inhibitor technology.

Edited by Tony Brooks
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4 minutes ago, Tony Brooks said:

 

We will disagree on that. 50% is the usually recommended maximum concentration because if you go higher the coolant looses its ability to carry as much heat away. Typically 33% is recommended by the manufacturers.

 

 

We will. Never mind. But please can you explain how the coolant looses its ability to carry heat, I think that contradicts the laws of thermodynamics because higher concentration raise the boiling  and freezing point of water.

TD'

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12 minutes ago, Tracy D'arth said:

We will. Never mind. But please can you explain how the coolant looses its ability to carry heat, I think that contradicts the laws of thermodynamics because higher concentration raise the boiling  and freezing point of water.

TD'

I understand that antifreeze has a lower specific heat than water. Nothing to do with latent heat (boiling and freezing point).

 

Here you go from Beta's website

General Aftercare

For Kubota Based Propulsion & Generating Set Engines, Beta Marine Recommend:

Clip

   
   
   
   
   

Engine Coolant Antifreeze

Always use a Mono Ethylene Glycol Based Extended Life Anti-freeze mixed 30 < 50% with water.

NB: Do not exceed an Anti-freeze mix greater than 50%, as the engine cooling efficiency will be detrimentally affected.

 

https://betamarine.co.uk/general-aftercare/

Edited by Tony Brooks
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7 minutes ago, Tony Brooks said:

I understand that antifreeze has a lower specific heat than water. Nothing to do with latent heat (boiling and freezing point).

 

Here you go from Beta's website

General Aftercare

For Kubota Based Propulsion & Generating Set Engines, Beta Marine Recommend:

Clip

   
   
   
   
   

Engine Coolant Antifreeze

Always use a Mono Ethylene Glycol Based Extended Life Anti-freeze mixed 30 < 50% with water.

NB: Do not exceed an Anti-freeze mix greater than 50%, as the engine cooling efficiency will be detrimentally affected.

 

https://betamarine.co.uk/general-aftercare/

You are correct Tony, I did not know that.

"Heat Transfer Efficiency - Glycol is 5-10% less efficient than water in transferring heat. However, this is more than recouped by the elimination of scale, dirt, and corrosion that can reduce heat transfer!13 Aug 2013"

TD'

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On my own boat I used to start with rather more than 50% so that over the life of the antifreeze 5 years in my case) it could be topped up with ordinary water. I never had a problem and the same with the central heating but I don't feel I can advise others to do that. But 50% still allows a lot of dilution before you get to 25% and that will normally be OK for most of the inland waterways in England and Wales.

Edited by Tony Brooks
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32 minutes ago, Tony Brooks said:

On my own boat I used to start with rather more than 50% so that over the life of the antifreeze 5 years in my case) it could be topped up with ordinary water. I never had a problem and the same with the central heating but I don't feel I can advise others to do that. But 50% still allows a lot of dilution before you get to 25% and that will normally be OK for most of the inland waterways in England and Wales.

Same here. Especially when you can buy concentrated red AF @ less than £30 for 20 litres delivered at the moment.

TD'

 

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3 minutes ago, Thomas C King said:

Short update as thanks. I did as Tony Brooks suggested. I'm not sure how much air is meant to come out when you bleed if there is a problem. It wasn't much. But, the temperature when running the engine doesn't go above ~70C now, both in our previous mooring spot and for the past three hours that we've been cruising. Hopefully that was the issue, thank you everyone :)

Thanks for the update, it relieves the tension of not knowing what was wrong.#

TD'

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