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


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Just now, Keeping Up said:

If the tank has plenty of internal baffles I don't think it makes a lot of difference.

Probably correct for modern engines designed to use a horizontal flow radiator when in a vehicel but if there is a chance the water pump was designed to use a vertical flow radiator I would not risk it because as Biz keeps telling us its no so much a pump but more a circulator.

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hi, on my lunch break I took another photo and a video (although I'm doubting whether it is any better than the prior photos, but I can take more after I finish work). In the photo below I have circled a small nut, is that likely to be the bleed valve? I was confused, because the skin tank looks just like it's a part of the actual hull. The wood ontop does indeed prevent further access, but it appears that the valve isn't under the wood? If that's the case, then we can bleed it and add coolant (once we've traced the pipes). Video here: https://photos.app.goo.gl/UanzghpJVA528Jnv9

 

image.png.d071cee67842562ef80cc2fd0359f11e.png

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1 hour ago, pearley said:

Beta say differently

Screenshot_20200708-123728.png

As do Barrus.

I think the term “top hose” exists for a reason, it’s just another form of heat exchanger after all.

 

 

Edited by Eeyore
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2 hours ago, Alan de Enfield said:

Hot in the bottom and as it rises it cools meaning the cooler water is taken from the top.

In a positively pumped circuit it probably makes no difference. I am however having some difficulty with the concept of hot water rising as it cools. Not the version of convection I had in mind. Hot at the top allows convection to work in parallel (same general direction of flow) as the pump. The engine water pump, as has already been said, is realistically only “giving an invitation to circulate” in what is invariably a much larger system than it was designed for; and needs all the help it can get.

Edited by Eeyore
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 The principle reason for circulating the water from the top of the engine to the top of the skin tank is that it is far easier to bleed air from the system with circulation this way because the engine pump is below the level of the top of the engine.

The pump is just a circulator, it has an impeller.

Not a positive displacement pump with one way valve/s and a diaphragm or piston.

But in a system with no air trapped, it will circulate the cooling water in either direction.

It is more logical to take advantage of the thermosyphon effect aiding the pump, the water descending in the skin tank as it is cooled will increase in density displacing the hot water from the top of the engine.

TD'

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52 minutes ago, Thomas C King said:

hi, on my lunch break I took another photo and a video (although I'm doubting whether it is any better than the prior photos, but I can take more after I finish work). In the photo below I have circled a small nut, is that likely to be the bleed valve? I was confused, because the skin tank looks just like it's a part of the actual hull. The wood ontop does indeed prevent further access, but it appears that the valve isn't under the wood? If that's the case, then we can bleed it and add coolant (once we've traced the pipes). Video here: https://photos.app.goo.gl/UanzghpJVA528Jnv9

 

image.png.d071cee67842562ef80cc2fd0359f11e.png

 

The circled item that you describe as a nut is very unlikely to be a bleed point if it really is a nut. If its a bolt 9setecrew head) then it might be but its position looks too close to  the hull to be typical. Usually the bleed thing is bigger that that and more or less in the middle of the tank's depth.

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

 

The circled item that you describe as a nut is very unlikely to be a bleed point if it really is a nut. If its a bolt 9setecrew head) then it might be but its position looks too close to  the hull to be typical. Usually the bleed thing is bigger that that and more or less in the middle of the tank's depth.

Oh joy. Do all skin tanks have a bleed valve/thing? Why would there be a nut or bolt there? Also, is that definitely the skin tank, or could it be the side of the hull with the tank on the outside? I'll have another look, I can see in the video that I didn't fully look across the top of the skin tank.

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11 minutes ago, Thomas C King said:

Oh joy. Do all skin tanks have a bleed valve/thing? Why would there be a nut or bolt there? Also, is that definitely the skin tank, or could it be the side of the hull with the tank on the outside? I'll have another look, I can see in the video that I didn't fully look across the top of the skin tank.

Not all skin tanks have a bleed, mine did not. All will need a way for air and gas to exit the tank. Mine had the coolant filler directly above the tank with a large diameter pipe joining the two so air and gas could always escape (another plus for an ex hire boat).

 

That "nut" is sitting on a ledge with a an up stand behind it running up to the uxter (swim) plate. The most likely explanation for that is the ledge s the top of the skin tank. The upstand is the hull, and the part the hoses join is the face of the skin tank.

 

I have no idea what that "nut" is. It seems to be silver rather than mild steel and its not brass like a radiator bleed screw might be. It is very small. It may even have been glued there for some unknown reason. I do have a rather nasty thought about it but will keep it to myself until more and better images are forthcoming.

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2 minutes ago, Tony Brooks said:

Not all skin tanks have a bleed, mine did not. All will need a way for air and gas to exit the tank. Mine had the coolant filler directly above the tank with a large diameter pipe joining the two so air and gas could always escape (another plus for an ex hire boat).

 

That "nut" is sitting on a ledge with a an up stand behind it running up to the uxter (swim) plate. The most likely explanation for that is the ledge s the top of the skin tank. The upstand is the hull, and the part the hoses join is the face of the skin tank.

 

I have no idea what that "nut" is. It seems to be silver rather than mild steel and its not brass like a radiator bleed screw might be. It is very small. It may even have been glued there for some unknown reason. I do have a rather nasty thought about it but will keep it to myself until more and better images are forthcoming.

"I do have a rather nasty thought about it but will keep it to myself until more and better images are forthcoming." - is that thought along the lines of, "don't remove it"?

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Certainly not until we get better images but more along the lines of what would be the need of a screw in that position where it looks as if the hull side would hinder a spanner. I just wonder if its location was forced on someone. If it were then maybe we might have a clue as to why the system seems to be devoid of coolant. (i think this is a new purchase).

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8 minutes ago, Thomas C King said:

"I do have a rather nasty thought about it but will keep it to myself until more and better images are forthcoming." - is that thought along the lines of, "don't remove it"?

I put a similar screw / bolt into the side of a bucket - did the job, worked a treat.

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Sorry, quick question, what would you like photos of specifically?

 

Also to clarify, I'm not sure if it's missing coolant, but some spluttered out of the tank (the right one) into the bilge. Hence the plan to add more.

Edited by Thomas C King
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We need a close up of that nut, a shot of whatever is below the wooden structure where we think the tank bleed point might be.

 

Then we need sufficient photos so we can work out exactly what pipes go where and how those two tanks are r are not connected to the system. I am beginning to suspect they may be related to the domestic hot water or heating system but as I can't see the pipework I don't know.

 

If its too difficult to get the shots then a drawing may show what is connected to what and where more easily.

4 hours ago, Detling said:

Mine is that way you put the hot coolant into the bottom of the skin tank which ten makes it's way throught the baffles and comes out of the top cooler.

 

The other reservoir and expansion tank look to me as though they are part of a sealed central heating system, although why you put one on a boat beats me.

At one time some calorifier suppliers used a plastic car type expansion tank in place of the PRV although if this is one of those I think its been replaced.

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An old friend and customer of mine was a pilot-captain of an air-sea rescue Short Sunderland flying boat out of Shannon Irelandy during ww2. In case they were shot up by an enemy plane they carried a pot mender and a pot mending kit. If they had been shot at he would go down into the hull to check for bullet holes and mend any he found. They were like little umbrellas that you poked through a hole, pulled up tight with washer and nut on the inside, all to prevent the plane sinking when alighting on the water. My old friend and customer did get shot up badly off the French west coast. The plane plumeted into the sea, he was the sole survivor, flung through the busted windscreen into the sea., the plane sank. He was in the sea for hours on end in his Mae-West, eventually rescued by a Potugese fishing boat. It ruined his future life with chronic circulation trouble. His car an Austin 1100 was fixed up with invalid controls.  Isn't that interesting. :unsure:

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Blowing up part of the picture and playing around with the contrast says to me that the circled bit is a bleed point for a skin tank. Looks like a length of tube welded to the top of the tank and threaded for a screw in square headed plug. That it is in the tank, not in the swim is more obvious

Jenmodified.png.226f2002da18f330b24d2d7bd1230a95.png

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2 minutes ago, Jen-in-Wellies said:

Blowing up part of the picture and playing around with the contrast says to me that the circled bit is a bleed point for a skin tank. Looks like a length of tube welded to the top of the tank and threaded for a screw in square headed plug. That it is in the tank, not in the swim is more obvious

Jenmodified.png.226f2002da18f330b24d2d7bd1230a95.png

 

I agree with you. Certainly looks like it. For the OP, what Jan has produced is a plug set into a stub of pipe. I would say definably the bleed point. It also shows its more in the position it would be expected to be in.

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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.

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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.

 

 

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