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dreadnought

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hi all,i have a bmc 1800 fitted in my nb,and every time i check the water level after cruising(when cold) i have lost water,about a pint,i no where its comming from i think,around the radiator cap there is a lot of rusty water staining like the cap is not sealing properly,do they fail ?     should i get a new one,if so where would i get one from,many thanks in advance

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Yes they do fail mine did. I bought a new one from a local motor factors. Tractor spares suppliers usually have them or Calcutt boats and ASAP supplies.

 

http://www.calcuttboats.com/

 

https://www.asap-supplies.com/

 

Most chandleries should stock them as well.

 

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That may well be the case on a boat with a large skin tank volume. The answer is to fit an expansion tank. If you have a Polar heat exchanger do not exceed a 4psi cap and if a Polar the 6PSI. Any more is likely to eventually split the rubber end caps.

Edited by Tony Brooks
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2 hours ago, dreadnought said:

when i take the cap off theres no coolant to be seen, so i top it up 

 

How much are we really talking about?

 

Most BMCs have a heat exchanger, Bowman or equivalent (if there is one) that uses far more than a pint between empty and full!

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On 13/05/2018 at 22:01, Mikexx said:

 

How much are we really talking about?

 

Most BMCs have a heat exchanger, Bowman or equivalent (if there is one) that uses far more than a pint between empty and full!

Not in the vast majority of narrowboats they don't.  They have a water cooled exhaust manifold that acts as a header tank that in an indirect (heat exchanger) raw water cooling system contains a heat exchanger core. On skin tank cooled narrowboats that core may or may not be present but if it is the manifold is only acting as a header tank, not a heat exchanger.  The 1.5 was also available as a direct water cooled unit and their manifold had nothng to do with heat exchangers.

 

If its not simply a volume of water in the system expanding problem its most likely air trapped in the system somewhere so manipulate all bends in hoses to try to let any trapped air escape and bleed the skin tank and

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13 hours ago, Tony Brooks said:

Not in the vast majority of narrowboats they don't.  They have a water cooled exhaust manifold that acts as a header tank that in an indirect (heat exchanger) raw water cooling system contains a heat exchanger core. On skin tank cooled narrowboats that core may or may not be present but if it is the manifold is only acting as a header tank, not a heat exchanger.  The 1.5 was also available as a direct water cooled unit and their manifold had nothng to do with heat exchangers.

 

If its not simply a volume of water in the system expanding problem its most likely air trapped in the system somewhere so manipulate all bends in hoses to try to let any trapped air escape and bleed the skin tank and

 

I bow to your greater knowledge. I guess I have only seen a few close up, and they had Bowman style tank/heat exchangers.

 

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12 minutes ago, Mikexx said:

 

I bow to your greater knowledge. I guess I have only seen a few close up, and they had Bowman style tank/heat exchangers.

 

Perfectly correct, either Bowman or Polar but calling the exhaust manifold water jacket cum header tank a heat exchanger is incorrect for the vast majority, but not all narrowboats. If a skin tank or keel cooling is in use then it is just a manifold/header tank and until you start counting pipes attached to it there is no visual way to find out which it is, both look identical.

 

The problem as I see it is that an inexperienced boater could read your post (and many others) and assume they have a heat exchanger. They then go on to state this as fact. This allows them to be identified as someone ripe for ripping off or when they ask on here and similar places it causes no end of confusion so they are likely to et an incorrect answer.

 

There are a few boats on the system that use a heat exchanger system with a skin tank but it involves another header tank and another water pump so more complications.

 

 

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39 minutes ago, Tony Brooks said:

Perfectly correct, either Bowman or Polar but calling the exhaust manifold water jacket cum header tank a heat exchanger is incorrect for the vast majority, but not all narrowboats. If a skin tank or keel cooling is in use then it is just a manifold/header tank and until you start counting pipes attached to it there is no visual way to find out which it is, both look identical.

 

The problem as I see it is that an inexperienced boater could read your post (and many others) and assume they have a heat exchanger. They then go on to state this as fact. This allows them to be identified as someone ripe for ripping off or when they ask on here and similar places it causes no end of confusion so they are likely to et an incorrect answer.

 

There are a few boats on the system that use a heat exchanger system with a skin tank but it involves another header tank and another water pump so more complications.

 

 

 

I took the heat exchange to be exhaust to water rather than a water to water device. I take your point.

 

Mine is then a large header tank!

 

My point still holds where the OP said he was just losing just a pint. In my case, and I assume for most others, the level might drop an inch, but that's about it.

 

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8 minutes ago, Mikexx said:

 

I took the heat exchange to be exhaust to water rather than a water to water device. I take your point.

 

Mine is then a large header tank!

 

My point still holds where the OP said he was just losing just a pint. In my case, and I assume for most others, the level might drop an inch, but that's about it.

 

But it all depends on the volume of water in the system. Some builders fit stupidly thick skin tanks that are not only inefficient but also contain  far more coolant than necessary. The larger the skin tank and the longer any pipework the greater the volume of coolant so the greater the expansion volume.

 

Its only on true heat exchanger engines that the fill to about 1" of the top is true.

 

There are cases where the expansion on Betas that have a larger exhaust manifold is so great when the engine cools down it draws air into the cooling pipes.

 

Air also expands more than coolant when heated so if air is trapped anywhere in the cooling system you cam get similar symptoms, which is why I mentions that possibility.

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On 13/05/2018 at 22:01, Mikexx said:

 

How much are we really talking about?

 

Most BMCs have a heat exchanger, Bowman or equivalent (if there is one) that uses far more than a pint between empty and full!

thats right what you say, but in mine you can only see about an inch into the bowman because there are pipes in the way

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