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Webasto issues


Steveb1312

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I have a thermo top c Webasto with an open header tank. Been running for numerous years fault free. Had an issue with the burner so swapped it out for a new one which solved the issue. Some months later the radiators were hot at the top only.! Presumed sludge so tried Disconnecting  the radiators and there was no sludge. The header rank inside is rusty and lots of bits floating about then the heater decided to run for a few mins then idle before the rads were hot and the re fire. I have this checked by Webasto dealer and was told the water is not flowing quickly enough and that the temperature is reached quickly as it’s slow moving causing the system to switch off idle and then restart shortly after. It’s inevitably not heating the rads sufficiently, I tried to remove the water pipes from the unit and force flush with a hose pipe this just filled the header and overflowed quickly. Allowing the water to flow out it was apparent there is a blockage in the pipe work but I have no complete drain down so my question is how quickly should the water flow through and would a hose pipe be too much pressure for the system and is it possible to swap from an open header to a sealed header tank to allow a bit more pressure and blast the pipes clean. If not is the only option to disconnect a rad from the front and blow it from that end? 

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First of all are you absolutely sure that there is not an airlock in the pipework, do you have any high spots where air can become trapped.

 

Secondly did you premix the antifreeze with water before putting it in the system.

 

I can see no reason that disconnecting the down pipe from the header tank and fitting a temporary cap and then disconnecting both water connection son the Webasto and putting a hose on one connection would cause any problems apart from only opening the hose tap gradually so the tap is restricting the flow to a degree and thus the pressure in the system. As someone opens the tap you can watch the water flow and judge when it seems fast enough. However it is likely to be a two pipe system so you may have to have one radiator's valves open at any one time so all rads get the full flow. Then you will have to open all the valves and then balance the radiators once the system is back working.

 

I would also flush in both directions.

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Definately no air in system, and when I dine this the water literally was only trickling and it wasn’t flowing very well at all. Just curious as to wether I can seal the header for the purpose of forcing the flow round the pipes I’m gna have to go from the very last radiator I think a send it out from that way as it just won’t clear from the unit in either direction. 

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7 minutes ago, Steveb1312 said:

Definately no air in system, and when I dine this the water literally was only trickling and it wasn’t flowing very well at all. Just curious as to wether I can seal the header for the purpose of forcing the flow round the pipes I’m gna have to go from the very last radiator I think a send it out from that way as it just won’t clear from the unit in either direction. 

 

I don't understand what you are trying to say.

 

1. As we don't know how your header tank is connected to the pipework we can't say just put a cork in its outlet to seal it and if you did and if there is a blockage that is a recipe for blowing the cork out and squirting water all over the cabin. Hence my saying to disconnect the pipe from the tank and cap it. My guess is that you will end up with an olive and loose nut on the pipe and compression caps for just that job are available. It will be similar if you have plastic piping but, depending upon the make you might need  a tool to allow you to open the coupling.

 

2. I read the original post as you wanting to flush the system, not the Webasto unit so if you disconnected the water pipes from the Webasto you have two open pipes so that allows you to flush the rads and pipes in both directions. It might be an idea to fit a length of hose running overboard to one of the open pipes so you don't flood the boat.

 

If you are now saying you think the Webasto is blocked then that is a different thing. I am not sure what type of water pump the Webasto uses but I suspect its a centrifugal one so  you will have the two open connections on the Webasto so you should be able to flush that as well. Centrifugal pumps won't stop water flowing through them.

 

I suppose that you have ensured the water pump is actually running when you turn the Webasto on.

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Yes sorry wat I mean is that the Webasto is pumping but the flow isn’t quick enough if I put a hose on one of the 2 pipes surely a nice steady flow should come out the other pipe? 
 

this isn’t happening it’s just trickling out the return or vice versa. 
 

also the pipe reduces from 22m to 15mm on the inlet and return so I presume it’s not flushing all the way through so to go from the opposite end of the system and flush out towards the pipes on the Webasto unit. 
 

can I flush from the top connector on one of the radiators and just open each valve in turn flushing backwards or would this cause any issues.? 

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I can't comment because I still don't understand. With both Webasto pipes disconnected you can flush or try to flush the boat's rads and pipe work and then the Webasto so you can eliminate one or the other.  Until you do that you won't know if any blockage is in the boat plumbing or in the heater unit.

 

In any case I said I THINK it will ba  centrifugal pump, it might not be and if not that can present a blockage. If it is  a centrifugal pump the impeller may be clogged with crud. That won't normally cause a blockage as such but will prevent circulation.

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Right sussed it out finally. I disconnected the Webasto pipes and ran them straight to a bucket of cold water and worked a treat perfect so Webasto is not the issue. I tried to flush through the inlet pipe and the flow coming out the return pipe was poor. Then tried flushing through the return pipe and the flow out the inlet side was much better but still not great. After this I left both these pipes open and into a large container and opened the radiator the furthest away from the Webasto and flushed via hose pipe this cleaned quite a bit of rusty water out. Opening each valve on the radiator cleaned both the return and the inlet side and refitted all pipes. Now seems to be working ok however I am running in the opposite direction to usual which doesn’t appear to be an issue but I will run it as it is for a day or so then swap it round again. So far so good 

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No I’m grabbing some tomorrow and will put it in whilst I swap the pipes round that I mixed up. Here’s hoping that it’s trouble free for a while again now. Is there any specific type to put in, there are plastic push fittings and copper to the rads. 

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59 minutes ago, Tonka said:

I use Fernox Alphi 2, it is recommended for central heating systems.

 

But the water In the central heating system in a house is unlikely to freeze, whereas in a boat that isn't lived on during winter it almost certainly will unless it contains antifreeze.

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32 minutes ago, cuthound said:

 

But the water In the central heating system in a house is unlikely to freeze, whereas in a boat that isn't lived on during winter it almost certainly will unless it contains antifreeze.

Fernox Alphi 2 has antifreeze in it. 

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