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Webasto coolant temperature problem


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Hi, everything had been working well with my Webasto thermo top C until a few days ago when it stopped getting up to temperature. It just gets warmish. There are no issues with startup, pump dosing is good, checked fuel lines, header tank is topped up, pump seems to be running as water/ coolant is circulating around rads and calorifier. It's just not heating up to full temperature. Any ideas? 

Thanks 

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10 minutes ago, Tracy D'arth said:

Anything to do with the ambient temperature dropping, so it needs more heat to heat the boat?

It crossed my mind but It's definitely more or less half the heat output than before and the hot water outlet from unit is only getting just warm even though burner itself is hot

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5 minutes ago, Tony Brooks said:

Missing info - how long had it been running for when you checked the temperature? I suspect it would need to be at least half an hour or so. It would do just as you say if its only minutes.

Yes it runs for a whole cycle (70mins or so) and still doesn't get up to temp. Previously water and rads were all v hot within that time frame 

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7 minutes ago, Lumisid said:

Yes it runs for a whole cycle (70mins or so) and still doesn't get up to temp. Previously water and rads were all v hot within that time frame 

That makes little sense because it suggests either the burner is not producing enough hear (you say its getting hot) or the water is not absorbing the heat and the most likely cause would be lack of circulation. If it were the latter then the boiler will overheat and shut down. So to me it suggests the burner s nt producing enough heat because if it was it should shut down on overheat.

 

I await the outcome with great interest.

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12 minutes ago, Tony Brooks said:

That makes little sense because it suggests either the burner is not producing enough hear (you say its getting hot) or the water is not absorbing the heat and the most likely cause would be lack of circulation. If it were the latter then the boiler will overheat and shut down. So to me it suggests the burner s nt producing enough heat because if it was it should shut down on overheat.

 

I await the outcome with great interest.

The burner housing and exhaust get v hot but the heat exchanger doesn't. I remember the heat exchanger getting hotter if I'm not mistaken...does this suggest anything? 

I would say there is circulation because there is coolant in the rads and they do heat albeit only a bit 

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11 minutes ago, Lumisid said:

The burner housing and exhaust get v hot but the heat exchanger doesn't. I remember the heat exchanger getting hotter if I'm not mistaken...does this suggest anything? 

I would say there is circulation because there is coolant in the rads and they do heat albeit only a bit 

Limescale?

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3 hours ago, smiler said:

Limescale?

Deionised water would have prevented this. I use it in both my engine cooling and Eberspacher driven central heating circuits. I paid about 12 quid for 20-25 litres - an insignificant enough cost that I don't recall.

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1 hour ago, Sea Dog said:

Deionised water would have prevented this. I use it in both my engine cooling and Eberspacher driven central heating circuits. I paid about 12 quid for 20-25 litres - an insignificant enough cost that I don't recall.

Yes I realise that 

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10 hours ago, Sea Dog said:

Deionised water would have prevented this. I use it in both my engine cooling and Eberspacher driven central heating circuits. I paid about 12 quid for 20-25 litres - an insignificant enough cost that I don't recall.

Oh, should I do something about my coolant, I don't expect boat has had any particular maintenance, and I just added a tiny bit of water out the tap to the water jacket in the Isuzu engine, I've done same with the reservoir which I think is the Webasto, I have not done anything to the radiators, one needs bled, but the boat is warm enough without messing about with the unknown when there is no chance of getting outside help.

I have some Halfords antifreeze but no deionised water, though I expect I could get some. I saw an RCR van servicing an engine recently, I could ask them what they could do for me, thinking about the stern gland, and even the PRM, though I believe some serious  work has been done on the drive, maybe a new propshaft, it was all a bit vague, and never seen any receipts. I can manage to change the fuel filter and the oil, but that's my limit, unsupervised.

Edited by LadyG
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13 hours ago, Lumisid said:

The boiler is new and has only been used since September, how likely is Limescale after a couple of months? 

Quite unlikely unless it was filled with extremely hard water.

Maybe worth draining down and use a descaling product to see if it helps.

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1 hour ago, LadyG said:

Oh, should I do something about my coolant, I don't expect boat has had any particular maintenance, and I just added a tiny bit of water out the tap to the water jacket in the Isuzu engine, I've done same with the reservoir which I think is the Webasto, I have not done anything to the radiators, one needs bled, but the boat is warm enough without messing about with the unknown when there is no chance of getting outside help.

I have some Halfords antifreeze but no deionised water, though I expect I could get some. I saw an RCR van servicing an engine recently, I could ask them what they could do for me, thinking about the stern gland, and even the PRM, though I believe some serious  work has been done on the drive, maybe a new propshaft, it was all a bit vague, and never seen any receipts. I can manage to change the fuel filter and the oil, but that's my limit, unsupervised.

Since 1960 I have been following what was standard industry practice for both cars and boats and been using ordinary tap water for central heating and cooling systems. It is only in the last 20 years or so has the use of pre-mixed coolant or deionised water for non-specialists applications become wide spread.  I am sure you will have no problems from topping up either system with tap water as long as you keep a 30% to 50% antifreeze concentration and change it at the applicavle intervals.

 

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15 hours ago, Tony Brooks said:

That makes little sense because it suggests either the burner is not producing enough hear (you say its getting hot) or the water is not absorbing the heat and the most likely cause would be lack of circulation. If it were the latter then the boiler will overheat and shut down. So to me it suggests the burner s nt producing enough heat because if it was it should shut down on overheat.

 

I await the outcome with great interest.

Would a partial air-lock cause those symptoms by restricting the flow of hot water ?

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10 minutes ago, Alan de Enfield said:

Would a partial air-lock cause those symptoms by restricting the flow of hot water ?

I have been considering that and can't rule it out but if the burner stayed on full power and the water flow was reduced I would expect it to cut out on boiler overheat because the water in the boiler should boil. That is my logic on it but may well be incorrect.

Edited by Tony Brooks
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When you filled the system up did you mix the antifreeze and water before filling the system. Because if you just poured water in and then poured antifreeze in it will not mix and could give the effect you have. Tony Brooks will explain it better then I can

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Just now, Tonka said:

When you filled the system up did you mix the antifreeze and water before filling the system. Because if you just poured water in and then poured antifreeze in it will not mix and could give the effect you have. Tony Brooks will explain it better then I can

Not sure I can because that mainly applies to single pipe and gravity systems. The hot antifreeze is far denser (heavier) than cold water so it sits in the bottom of the pipes and can't rise up through the cold water into the rads where as a properly mixed liquid will have the same density so the hotter parts will rise up through the cold. A decent pump should force circulation (not so sure about the upright Alde one though).

 

In this case even if the antifreeze is stratified in the system and its creating problems for the pump to circulate it then the boiler should overheat and presumably cut out. I long ago learned theory is not always a foolproof method of diagnosis but can illuminate it so I am way of saying it is not stratification, we will hopefully see in time.

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1 hour ago, Tony Brooks said:

I have been considering that and can't rule it out but if the burner stayed on full power and the water flow was reduced I would expect it to cut out on boiler overheat because the water in the boiler should boil. That is my logic on it but may well be incorrect.

This happened when I first commissioned it. There was an airlock and the boiler shutdown. I sorted that and it has worked fine ever since, up till now

 

1 hour ago, Tonka said:

When you filled the system up did you mix the antifreeze and water before filling the system. Because if you just poured water in and then poured antifreeze in it will not mix and could give the effect you have. Tony Brooks will explain it better then I can

Yes I mixed it all before filling system

I’m going to double check the fuel line today and double check the dosing pump and make sure enough fuel is getting through

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4 hours ago, Lumisid said:

 

Yes I mixed it all before filling system

I’m going to double check the fuel line today and double check the dosing pump and make sure enough fuel is getting through

To my logic it seems far more like a lack of heat energy in the combustion than anything else and as it stays running it suggest lack of fuel to me.

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4 hours ago, Tony Brooks said:

To my logic it seems far more like a lack of heat energy in the combustion than anything else and as it stays running it suggest lack of fuel to me.

I checked the fuel line today and it seemed good. I’m going to take filter apart tomorrow...

Just to add there is no copper pipe inthe line between fuel filter to dosing pump to heater- its all connected with rubber hose 

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It can only be not enough fuel or the heat energy  is being dissipated too quickly if the heater body is not getting hot. If you disconnect the dosing pump from the heater and connect the output of the pump into a jar you can check how much fuel is coming through. If you get a good squirt each time the pump ticks it is probably OK. They are fixed delivery, each time it pulses you get so many cc. Check that after the heater gets up to temperature the pulse rate doesn't slow down. I have found it helpful in the past to wire an LED indicator  in parallel with the pump so you can see when it ticks. I also wired an LED indicator in parallel with the heater. By just looking at the LED's I could see if everything was going normally as my heater was in the engine compartment. Remember that with lower ambient  temperatures the rads will dissipate much more heat than in the summer. On my current setup if the boat is cold or near freezing the heater will run flat out for several hours before it shuts down whereas when it is warmer it is only about an hour.

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1 hour ago, Lumisid said:

Just to add there is no copper pipe inthe line between fuel filter to dosing pump to heater- its all connected with rubber hose 

Change it - it's a periodic anyway on rubber hoses, so your work won't be wasted, and one of the age failure mechanisms is swelling, which could be the cause of any fuel starvation.

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