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I've got an Isuzu 55 marine engine I've been told they are prone to air locking has anyone else had this problem I can't get hot water off the engine has anyone got any ideas tried water pump seems fine try blowing it round with hose pipe but still are lock somewhere any ideas please

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1. does it have a calorifier connected to the engine cooling system?

 

2. Its not the engine that air locks but the cooling system that has little to do with the make and model of engine and everything to do with the system design so we need to locate a high point in the calorifier pipework that can trap air. A photo of the calorifier and all its pipework may help locate such a point.

 

 

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Hi Tony thanks for the reply it has a cauliflower system on it it I've taken the top off at the highest point and blew through with water it is an upright cauliflower system not getting no out of skin tank size neither

Can post pictures earliest Saturday if you need to have a look and tell me if I am going wrong somewhere

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Just now, Animal said:

Hi Tony thanks for the reply it has a cauliflower system on it it I've taken the top off at the highest point and blew through with water it is an upright cauliflower system not getting no out of skin tank size neither

If you took the pipe off at the highest point on a vertical calorifier you just took the hot water out pipe off. The coil or coils connections are on the side very roughly in the middle. I bet the upper one on the engine coil has no way of venting air so once again a photo will help - I bet its all boxed in

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Sorry Tony I did mean a highest point of the cauliflower not of the tank plus I do have a auto vent on that top pipe as well but didn't seem to do nothing will put pictures app on Saturday for you thank you very much for your help very much appreciated and yes is a little bit boxed o  

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1 minute ago, Animal said:

Sorry Tony I did mean a highest point of the cauliflower not of the tank plus I do have a auto vent on that top pipe as well but didn't seem to do nothing will put pictures app on Saturday for you thank you very much for your help very much appreciated and yes is a little bit boxed o  

 

Unless you means something very different you still took off the hot outlet of the calorifier, not the top engine coil connection.

 

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The engine coil may be the upper one  or you may have a single coil calorifier.

 

There is no point in fitting an auto-bleed valve to the hot outlet at the top, the domestic pump will usually purge air from the system. You need a bleed vale at the top coil connections but if its all boxed in I would not use an auto-valve.

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The hot water outlet with a PRV is different water to the engine coolant.  Taste it, then taste a tiny amount of coolant from the header tank.  Don't taste lots because glycol  is not good for you in quantity.  The PRV water will taste OK.  The coolant will taste sweet from the glycol in the antifreeze.  

 

You need to get the air out of the coolant pipes, not the water pipes, so if the water you are getting out does not taste like coolant you are not bleeding the right thing.

As Tony asked,   send pictures of everything.  Engine, pipework, calorifier, skin tanks, header tank at least.

 

N

 

 

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Yeh - and reduce your hot water supply by half and ensure loads of air gets trapped in the tops of the coil loops.

 

Is that gate valve turned on but I think that is the central heating coil. You want the rubber hoses but I can't see exactly how and where they connect to the engine.. On the face of it they look a if they should self bleed but not sure about the parts I cant see.

 

 

Ita lso looks as if the central heating coil is connected to a skin tank unless its a bulkhead.

 

 

 

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Stating the obvious; each heating coil has an inlet and an outlet.

 

Check that the source of heat, (engine, diesel heater, whatever), goes from the source to the lowest coil connection of each coil in the calorifier.

 

Air is lighter than water, therefore it "floats" and it is almost impossible to push air "downhill" so you want the water flow  to go "uphill" when it will push the air ahead of it.

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48 minutes ago, Animal said:

Hi Tony so can we cylinder be laid down then to stop air locking plus I've blown water straight through one of them pipes to 3 airlock fills the header tank up up I

Look at the diagram I posted, particularly the coils, and consider where any air will go if you laid it on its side. Turning on its side will only make air locking worse.

 

Both rubber hoses run uphill away from the coil so air should be pushed up into the engine. It seems you are getting hot water to the coil but PERHAPS not away from it bit I think you are simply not waiting long enough to heat the domestic water in the calorifier. The return from the coil will be cold for a while after starting because 1. the coolant is cold and 2 all the heat is given up to the domestic water. You need to run the engine at 1000 rpm + for probably well over half an hour and perhaps longer to get hot water.

 

It is possible the return hose is not connected to the correct place on the engine but this is unlikely as the feed is getting hot.

 

Are you new to boating, is this boat new to you? If you want help we need to know a lot more than you gave us at the start so we can make sensible suggestions. That includes a bit of history.

 

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2 hours ago, Animal said:

someone said to me that these cylinders can be laid down to stop a locking would that be correct

Nope. It would be incorrect.
 

Firstly, horizontal cylinders are made to be fitted that way, with the internal coils designed for a horizontal orientation. Yours is a vertical calorifier which, if laid on its side, would add greatly to your woes. Secondly, horizontal calorifiers are less efficient. 

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1 hour ago, Tony Brooks said:

If you want help we need to know a lot more than you gave us at the start so we can make sensible suggestions. That includes a bit of history.

 

^^^^This^^^^

 

My thoughts too. 

 

That calorifier looks really old and well used so it would be reasonable to surmise it has given many years of good service.  So the question that leaps to my mind is how come it stopped? What did you do that stopped it working? Some history of the fault, PLEASE!!

 

 

 

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9 hours ago, WotEver said:

Nope. It would be incorrect.
 

Firstly, horizontal cylinders are made to be fitted that way, with the internal coils designed for a horizontal orientation. Yours is a vertical calorifier which, if laid on its side, would add greatly to your woes. Secondly, horizontal calorifiers are less efficient. 

That's what I thought its someone told me it would be ok I said you couldn't lay it down thanks anyway 

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12 hours ago, Mike the Boilerman said:

 

^^^^This^^^^

 

My thoughts too. 

 

That calorifier looks really old and well used so it would be reasonable to surmise it has given many years of good service.  So the question that leaps to my mind is how come it stopped? What did you do that stopped it working? Some history of the fault, PLEASE!!

 

 

 

 

If you are correct the coil could be well furred up so it would take a long time to heat the water but on the other hand it would give up less heat so the return to the engine shoudl be warm.

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If there is no flow through the calorifier, then the heat will pretty much stop being transferred (the hot water won't be flowing). So in that case I would expect the pipes to get really hot where they come out of the engine, but be pretty cool where they enter the calorifier.

 

If they are still hot at the calorifier entry point, then I think it is what Tony has stated; you aren't running the engine for long enough. All of the heat in the pipe is being transferred to the calorifier, so the return is cool.

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