Airlock Isuzu 55

[Tony Brooks]

20 minutes ago, David Mack said:

I seem to recall @blackrose added the second skin tank because he had insufficient cooling capacity.

 

Quite possibly, but that does not mean that he now has more than enough capacity, and it does raise the issue of being more difficult to bleed the interlink pipes.

[blackrose]

8 hours ago, David Mack said:

I seem to recall @blackrose added the second skin tank because he had insufficient cooling capacity.

 

Yes that's right, I added the second tank about 10 years ago. It's a 55hp engine, now with around 13ft2 of skin tanks. 

[blackrose]

I still haven't resolved this problem, although everyone is telling me that a pressurised engine coolant reservoir (even when it's stone cold) isn't a problem.

 

The main issue I have is that when running the engine the return pipe & hose from the calorifier isn't getting hot so no hot water from the engine and I've no idea how to remove any airlock. I'm reluctant to remove any hoses from the engine while it's running after scalding myself last time.

[Tracy D'arth]

2 minutes ago, blackrose said:

I still haven't resolved this problem, although everyone is telling me that a pressurised engine coolant reservoir (even when it's stone cold) isn't a problem.

 

The main issue I have is that when running the engine the return pipe & hose from the calorifier isn't getting hot so no hot water from the engine and I've no idea how to remove any airlock. I'm reluctant to remove any hoses from the engine while it's running after scalding myself last time.

Remove hose/union from calorifier very gently.

 

Most air locks on calorifiers are due to the mistaken idea that the flow goes to the top of the coil. It much easier to feed the water in at the bottom and then the air comes out easily from the top connection.  Its not a gravity circuit, the pump moves the water but it will not move air.

[blackrose]

24 minutes ago, Tracy D'arth said:

Remove hose/union from calorifier very gently.

 

Most air locks on calorifiers are due to the mistaken idea that the flow goes to the top of the coil. It much easier to feed the water in at the bottom and then the air comes out easily from the top connection.  Its not a gravity circuit, the pump moves the water but it will not move air.

 

Could you be a bit more specific please? Remove flow or return hose/union from the calorifier and should I do that with the engine running or switched off?

 

The thing is that it's been fine for 18 years so I'm not sure if it's been incorrectly installed?

24 minutes ago, Tracy D'arth said:

Most air locks on calorifiers are due to the mistaken idea that the flow goes to the top of the coil. It much easier to feed the water in at the bottom and then the air comes out easily from the top connection.  Its not a gravity circuit, the pump moves the water but it will not move air.

 

What you say here is interesting because I thought most heat exchanger systems plumbed hot flow in at the top and cold return at the bottom, forcing the water to go against its natural convection path, slowing the flow and thus maximising thermal exchange. That's the way my skin tanks are plumbed for example.

Edited July 30, 2023 by blackrose

[Mike Adams]

Find the highest point in the pipework between the engine and calorifer, get a central heating bleed nipple and make up a tee piece sized for the rubber tube bore. Mine was 15mm or 16mm bore hose. cut the hose and fit with hose clips. you can add olives to the pipe and just solder them on to make a more secure connection. You should be able to loosen the bleed screw when the engine is hot and get any air out. I did this on my set up on both pipes because the route to the calorifier went up from the engine and down again but I didn't need it so far. I think my first step would be to disconnect the calorifier pipes from the engine and flush though first to ensure there is no blockage.

[Tracy D'arth]

2 hours ago, blackrose said:

 

Could you be a bit more specific please? Remove flow or return hose/union from the calorifier and should I do that with the engine running or switched off?

 

The thing is that it's been fine for 18 years so I'm not sure if it's been incorrectly installed?

 

What you say here is interesting because I thought most heat exchanger systems plumbed hot flow in at the top and cold return at the bottom, forcing the water to go against its natural convection path, slowing the flow and thus maximising thermal exchange. That's the way my skin tanks are plumbed for example.

Skin tanks are cooling water, the reverse of heating. So flow is downwards as the water cools.

Not "incorrectly installed" just not optimum for bleeding air out. You can pump water up displacing air but you cannot pump air down displacing water, logic prevails.

[ditchcrawler]

1 hour ago, Mike Adams said:

Find the highest point in the pipework between the engine and calorifer, get a central heating bleed nipple and make up a tee piece sized for the rubber tube bore. Mine was 15mm or 16mm bore hose. cut the hose and fit with hose clips. you can add olives to the pipe and just solder them on to make a more secure connection. You should be able to loosen the bleed screw when the engine is hot and get any air out. I did this on my set up on both pipes because the route to the calorifier went up from the engine and down again but I didn't need it so far. I think my first step would be to disconnect the calorifier pipes from the engine and flush though first to ensure there is no blockage.

I have similar but on a 15mm copper pipe, The heating coils on my calorifier are higher than the engine. I just warm the engine to expand the coolant and open the bleed screw, done.

[blackrose]

1 hour ago, Mike Adams said:

Find the highest point in the pipework between the engine and calorifer, get a central heating bleed nipple and make up a tee piece sized for the rubber tube bore. Mine was 15mm or 16mm bore hose. cut the hose and fit with hose clips. you can add olives to the pipe and just solder them on to make a more secure connection. You should be able to loosen the bleed screw when the engine is hot and get any air out. I did this on my set up on both pipes because the route to the calorifier went up from the engine and down again but I didn't need it so far. I think my first step would be to disconnect the calorifier pipes from the engine and flush though first to ensure there is no blockage.

 

Ok thanks, I'll try that. The only issue I see is that I'm pretty sure the highest point on both pipes is at the engine connections.

 

1 hour ago, Tracy D'arth said:

Skin tanks are cooling water, the reverse of heating. So flow is downwards as the water cools.

Not "incorrectly installed" just not optimum for bleeding air out. You can pump water up displacing air but you cannot pump air down displacing water, logic prevails.

 

Ok, I'm not sure I understand the difference as both are circulating hot coolant through a heat exchanger in order to lose heat to a cooler medium on the other side? That's my logic anyway.

 

I understand what you're saying about my setup not being optimum for bleeding air, but if I can put the bleed nipples on both flow and return pipes at the highest point as others have suggested then hopefully that will solve the issue.

Edited July 30, 2023 by blackrose

[blackrose]

I solved the problem today. Looking at some pictures from the original sailaway I saw that the builders had done a shit job with the plumbing which I didn't realise at the time. The calorifier loop from the engine was sagging so bound to cause an airlock, though why it took 18 years to happen I don't know. The engine to calorifier loop isn't the one marked with flow & return arrows in the picture - that's the Webasto circuit.

 

Anyway I drained some coolant out the system in the engine room, took the flow & return pipes off and blew though the circuit to make sure it wasn't blocked. Then I removed the staircase in the cabin at the stern which now covers the pipework and straightened the pipes cutting them shorter. I also reconnected them with the flow to the bottom of the calorifier and return from the top to help bleeding as Tracy advised. Then refilled the system and ran the engine. Both flow and return pipes are now getting hot. It's nice when a fix works first time. Thanks all.

 

 

Edit: I haven't added bleed nipples but if it happens again I'll add them on the engine room side.

Edited August 6, 2023 by blackrose

[Mike Adams]

That's the problem with unsupported plastic pipes - they are going to sag over time. I don't think I would trust them on an engine cooling circuit. Rather use copper or hose but it's good you've fixed it.

[Tracy D'arth]

37 minutes ago, blackrose said:

I solved the problem today. Looking at some pictures from the original sailaway I saw that the builders had done a shit job with the plumbing which I didn't realise at the time. The calorifier loop from the engine was sagging so bound to cause an airlock, though why it took 18 years to happen I don't know. The engine to calorifier loop isn't the one marked with flow & return arrows in the picture - that's the Webasto circuit.

 

Anyway I drained some coolant out the system in the engine room, took the flow & return pipes off and blew though the circuit to make sure it wasn't blocked. Then I removed the staircase in the cabin at the stern which now covers the pipework and straightened the pipes cutting them shorter. I also reconnected them with the flow to the bottom of the calorifier and return from the top to help bleeding as Tracy advised. Then refilled the system and ran the engine. Both flow and return pipes are now getting hot. It's nice when a fix works first time. Thanks all.

 

 

Edit: I haven't added bleed nipples but if it happens again I'll add them on the engine room side.

Glad to be of help.

 

Is that a gate valve and stub of an air vent pipe fitted to the Webasto flow pipe?  If so it would be better on the return, top, pipe.

The guy that did that installation was no plumber!

[blackrose]

18 minutes ago, Mike Adams said:

That's the problem with unsupported plastic pipes - they are going to sag over time. I don't think I would trust them on an engine cooling circuit. Rather use copper or hose but it's good you've fixed it.

 

The pipes were sagging from the start. That picture is from 18 years ago. 

7 minutes ago, Tracy D'arth said:

Glad to be of help.

 

Is that a gate valve and stub of an air vent pipe fitted to the Webasto flow pipe?  If so it would be better on the return, top, pipe.

The guy that did that installation was no plumber!

 

Yes that is a gate valve. I've added a kuranda fan heater to the Webasto flow & return to maximise kW capacity to the full 5kW of the Webasto, so that pipe is now one of the connections to the kuranda and there's another pipe Td off from the bottom run.

Edited August 6, 2023 by blackrose