Filling / Bleeding Diesel Heater?

[Tim Good]

Ok so this is my first time doing this. I have an old webasto DW80.

How do I:

1: get all the existing water out of the system given that the heater and water values are higher then most of the water circuit.

2: once empty fill the system with pre mixed antifreeze mixture and bleed out air locks?

The manual just says do it with the hint of using a watering can held up high as a temporary header tank.

Any other tips?

 

[David2452]

Ok so this is my first time doing this. I have an old webasto DW80.

How do I:

1: get all the existing water out of the system given that the heater and water values are higher then most of the water circuit.

2: once empty fill the system with pre mixed antifreeze mixture and bleed out air locks?

The manual just says do it with the hint of using a watering can held up high as a temporary header tank.

Any other tips?

Yes, dump the header tank and fit a pressure system. If you wish to retain the header, leave the outlet from the heater un tightened and with the pump running pop it off for a second, this will purge the heat exchanger. Arranging a temporary power source for the circulation pump is a good idea as you can do it all without getting scalded.

 

[Tim Good]

If I can provide a temp supply to the pump could I just feed a hose to the intake of heater that leads to a bucket of antifreeze mix. Then fit the heater outlet as normal and run the pump? Would that pump the system full or at least full enough to cause an air lock and it will self bleed afterwards?

 

[David2452]

If I can provide a temp supply to the pump could I just feed a hose to the intake of heater that leads to a bucket of antifreeze mix. Then fit the heater outlet as normal and run the pump? Would that pump the system full or at least full enough to cause an air lock and it will self bleed afterwards?

Yes, that's how I used to fill systems before I started to use pressure systems a few years ago, if you put a temporary (restricted) hose on the outlet back into the bucket and let it run for a while it will allow you to go around any bleed points in your system. Remenber the pump is not self priming so the bucket needs to be above the heater by a couple of feet if possible, I used to use a cistern with the feed taken from a fitting at the bottom, in fact I still do on my test bed.

 

[Tim Good]

Ok I think I should be able to sort that out. I've just hooked it all up and put a hose pipe onto the hose that the enters the system from the heater. I then let it run under water came back out of the heater and filled the header tank. This is just with normal water at this stage. I'd have thought that would have pushed all air locks out. So now to test it works before filling with antifreeze solution.

I reconnected and run it ups it starts, does its thing, gets hot and make some loud gurgling noises like the water is boiling in the heater exchanger. Anyway it then seems to blow its dan hard and shut down and sleep for a bit and then starts up again 5-10 mins later. Presumably when the temp sensor tells it that it needs to get the water up to temp again.

Anyway sounds like it might be running properly. Only one issue. No hot air. The heater exchanger fan units just keep blowing cold.

Pic for your reference:

View attachment 48542

 

[David2452]

Both the gurgling and the early overheat shut down indicate an airlock in the exchanger, see comment post # 2 about removing the hose from the heater outlet above. Also you may well have an airlock in the matrix, they can be a bugger to purge in a header system and the reason I now only fit pressure systems.

 

[Tim Good]

Both the gurgling and the early overheat shut down indicate an airlock in the exchanger, see comment post # 2 about removing the hose from the heater outlet above. Also you may well have an airlock in the matrix, they can be a bugger to purge in a header system and the reason I now only fit pressure systems.

How do I know this one is not pressurised? It does have a pressure gauge on the right side of the header tank on my upside down photo. Or does the fact it has a header tank automatically mean it isn't pressurised?

 

[Tim Good]

Both the gurgling and the early overheat shut down indicate an airlock in the exchanger, see comment post # 2 about removing the hose from the heater outlet above. Also you may well have an airlock in the matrix, they can be a bugger to purge in a header system and the reason I now only fit pressure systems.

Ok we may be getting somewhere. I did as you said and took 12v directly to the water pump. Nothing. Fortunately I have a spare one on an old unit I bought for spares. I did wonder why no fault code would show for defective water pump but having looked; there is not fault code for water pump. Everything else apart from the water pump.

I'll replace and report back.

 

[David2452]

You can recognise a pressurised (closed system) because it will have a filling loop usually in braided stainless from the potable cold water with a couple of 1/4 turn valves and a non return valve, also thre will be an accumulator and a PRV somewhere in the system. What you seem to have is a self presurising closed loop system rather than a standard vented one (assuming the header tank has a pressure cap). As the temperature rises the pressure will increase, it will probably run at about 0.25 to 0.5 bar when hot as apposed to the 1.5 bar of a true pressurised system which is cold pre pressurised via the filling loop to around 1 bar.

 

[Tim Good]

Thanks for clarifying. Yes the header has a pressure cap and then above the gauge is a red cap that spins with a bit of force and then snaps back down again. Assume that is some sort of pressure cap also.

 

[Tim Good]

David,

I am going to pump in the anti freeze but is there any easy way to get rid or drain all the existing fluid from the system? the heater and header tank are the highest points. I could connect a self priming whale pump to it but wondered if you have a better trick?

 

[David2452]

Use the same method, only with pure water until it runs clear (maybe reverse the flow), then do it again, only recirculate through the container with some Rdlyme to descale the internals of the matrix / rads and heat exchanger, then just pump the AF round until you see the colour to displace the Rdlyme or wtaer.