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LondonRascal

Possible Thermostat Issue...

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I took Trixie for her first proper run out today, and noticed that the temperature gauge was only reading about 50c tops. Even when left at a high tick over for about an hour it did not climb further.  I then had the engine cover up and found some coolant dribbling from one of the two pressure caps, and this appears also where the thermostat is.

Please see the video below - as it could at the vest least need a new pressure cap, but do others feel that I should also be looking at the thermostat itself?

 

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Hi Robin, you are on the right lines, symptoms are exactly those of a thermostat stuck open and I suspect you are also correct about the newly cleaned out heat exchanger causing it to now run even cooler than before. The cap may well have been letting by during the high temp moments going over Breydon etc but a new one is never a bad idea anyway.

 

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Robin, I suspect your diagnosis is right about the thermostat being stuck open, however you will be surprised to find the thermostat is not where you think it is. When Nanni marinise the Kubota engine and add the heat exchanger they move the thermostat. If you follow the blue pipe that comes of just under where the pressurised cap is, you will see it goes to the heat exchanger. Where it goes into the heat exchanger there is a smaller rectangular section that end of the heat exchanger with four bolts in it. The thermostat is housed in there.

I only know this because after a blast across Breydon one day mine got stuck open and I had the same problem with the temp not getting past 60 degrees. I went into Peachments and purchased a new thermostat and a gasket and when the sales guy put the gasket on the counter it was rectangular and far to big to fit where you would logically conclude it is housed. Luckily he put me right and I didn't try stripping down the wrong area.

See attached pic of where mine is and where I'm sure you will find yours.

1493139709_ThermostatHousing.thumb.jpg.17f237a54ae21a2e0bf45f52c88331fd.jpg

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From experience be very careful trying to remove those 4 bolts.

All 4 sheared instantly when attempting removal on our Nanni. 

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Notice on ECIPA's photo that "your" pressure cap has been replaced by a threaded plug, as the pressure cap is not necessary and tends to dribble, as you can see! The main pressure cap is on the heat exchanger, where you also top up the system.

On the permanent plug is a smaller nut, used for bleeding air when topping up with coolant. Peachments will supply you with one of these plugs, or another solution is simply to buy a pressure cap of a higher setting (perhaps 10lb instead of 7lb, in the hope of stopping the dribble.

These early Nanni engines will always run cool unless they are running under a load. If you are just running it in neutral on the quay, then a temperature of 50 is no surprise.

 

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On my engine, its not shown on the picture, but off to the left where the second fill point is, there is actually a second plug fitted. The bleed nut has been removed and a 90 degree elbow fitted and then a rubber hose leading of to a header tank where the pressure cap is fitted. I have attached a picture taken of a sister hire boat to mine. Where the yellow highlight is shows the arrangement I'm on about, except mine is actually attached on the other outlet. My expansion tank is actually fitted behind the area shown in green and access to the fill point is therefore outside the engine bay. I'm assuming this was done to provide extra capacity of coolant as well as allowing the hirers to check the water without entering the engine bay.

The reed filter setup is such that it would never have needed checking by a hirer during the course of a hire, and certainly could never have been cleaned out without at least some hand tools. You can see the filter bowl, which has the top bolted down, so a spanner at least is needed to open this and clean it out. This is actually the secondary filter. The raw water intake is via a very large diameter pipe topped off with a very large nut as shown in red. Inside this tube is about 2ft of gutter down pipe which some one has painstakingly drilled hundreds, if not thousands of tiny holes. This acts as the primary filter and has such capacity that it never gets blocked. Very rarely do I get anything get as far as the swirl pot.

In normal operation my engine from cold will get to 60 degrees fairly quickly in a linear fashion and then stay there for about 25 mins, then continue on again in a linear fashion to just under 80 degrees. I assume the pause is where the thermostat just starts to open and the calorifier is then put into the loop and acts as secondary cooling until the water gets up to temperature. Once the hot water reaches 60 degrees then the whole system continues to warm up further and the thermostat continues to open more until it maintains the ideal operating temperature. If the engine Is started an hour or so after a few hours of running then the temperature gauge goes in a linear manner all the way to 80 without pausing at 60 degrees for a while, presumably because the calorifier is already hot and unable to provide any secondary cooling.

DSCF0973.JPG

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Hi Robbin The cap on the engine is not a pressure cap, it is a blanking cap if you twist it off it should be a plain cap with no spring underneath, the pressure cap which has a spring with a cap under the spring and is loose is on the top of heat exchanger it will have a 1/4 inch dia tube protruding mid way between the two seats, if this hasn't a rubber pipe connected and is just plain   get a hose pipe that fits it and direct it into a container (plastic milk bottle is good you can see the level of coolant), or you my already have a expansion tank connected to it, this allows the coolant to pass into the container when engine gets hot and allows the coolant to be sucked back into header tank when engine cools so you have max cooling and no loss of coolant, alternately you should have a space in top of heat exchanger coolant level to allow for expansion if you fill up to the top it will just push it out into the bilges. To check if thermostat is working start up from cold and place your hand on the hose that runs from thermostat housing to heat exchanger, if working it should stay cool then when thermostat opens at set temp it will get hot quickly stat ok, if it gradually gets warmer and warmer then  it shows that thermostat is open and allowing coolant to circulate when cold, ie faulty. Most thermostats have a small ball that allows for a slight flow this allows any trapped air to pass. Some engines won't have a cap but a plug/bung ie older engines it's there for refilling and bleeding when cooling system has been emptied, no need to take of for checking once bleed and filled to the top if you do the rubber washer deteriorates then leaks. John

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Whatever it is, Robin will get the parts, one of us will see to it during ‘B.A’s forthcoming AMP

Of course the real issue with Trixie’s engine?

Yep, it’s french - nuff said 

Griff

 

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At least it's the finished article though. When people write software they "Beta" test it first and iron out all the problems before releasing it to the public. :default_rofl:

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Maybe so but I’ll keep trying to support British jobs rather than french ones

Griff

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1 hour ago, BroadAmbition said:

Whatever it is, Robin will get the parts, one of us will see to it during ‘B.A’s forthcoming AMP

Of course the real issue with Trixie’s engine?

Yep, it’s french - nuff said 

Griff

 

Bit like the engine in the griff tile van ..

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