Webasto smell of diesel on startup?

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Simon F

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Hello All,

When my Webasto Air Top Evo 40 starts up and when it shuts down, there's a smell of diesel in the cabin for about a minute. When it's running, it's fine. Even after hours of running it, there's no smell. It's mounted in the cockpit locker and the exhaust exits through the transom and seems sound. I've started it up while closely observing it and there doesn't seem to be a corresponding smell in the cockpit locker on startup or a big plume of exhaust smoke from the exhaust outlet in the transom, so my first theory, (that leaked exhaust was finding its way into the air intake) seems to be wrong. Surely there's no way the heater can generate the smell in the heat exchanger is there? It would happen constantly rather than just for a minute if that was what was happening wouldn't it?

I've experimented with holding the CO detector in the duct output in the cabin and in the cockpit locker but it hasn't tripped. I'm not keen on the smell and I'd get it looked at, but no one in Brighton seems to service or repair the heater.

Any thoughts?

Thanks

Simon
 
Check fuel lines, fuel pump and fuel filter. Replace if there is an issue.

Replace the unit if suspect. I beleive webastos can be serviced but parts can be expensive.

I bought a vevor 5kw version for about 100 quid or so. 2kw versions were about 70.

Lots of chinaspacher options on fleabay etc.
 
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Boater Sam said:
Check that the silencer can is not an automotive one with a tiny condensate drain hole. These should never be used inside a boat.
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Yes, it seems to be all marine grade stuff. No leaks that I can smell on startup. the smell seems to be internally generated but I can't see how that's possible - the two circuits are totally seperate.
 
I note that you say the smell on shutdown is of diesel, but your search has been for potential exhaust ingress into the heating air system. Exhaust (burnt diesel) smells different to unburnt diesel fuel pong, and the two will have different potential paths into . Which is it you smell?

Could there be a path by which diesel fuel (rather than exhaust gas) is weeping into the 'domestic' side of the heating system?
Could the smell of diesel in the cabin on shutdown be arriving there by some route other than the blown heating air, perhaps?
Is the air intake for the domestic hot air side of the system taken from the cabin (recirculating) or 'fresh' from elsewhere (the locker?), and if elsewhere, is that intake in the same space as the combustion air intake?
Does the smell on shutdown happen after it has completely shutdown, or while it is going through the shutdown procedure?
 
LittleSister said:
I note that you say the smell on shutdown is of diesel, but your search has been for potential exhaust ingress into the heating air system. Exhaust (burnt diesel) smells different to unburnt diesel fuel pong, and the two will have different potential paths into . Which is it you smell?

Could there be a path by which diesel fuel (rather than exhaust gas) is weeping into the 'domestic' side of the heating system?
Could the smell of diesel in the cabin on shutdown be arriving there by some route other than the blown heating air, perhaps?
Is the air intake for the domestic hot air side of the system taken from the cabin (recirculating) or 'fresh' from elsewhere (the locker?), and if elsewhere, is that intake in the same space as the combustion air intake?
Does the smell on shutdown happen after it has completely shutdown, or while it is going through the shutdown procedure?
Click to expand...
Hi,

Thanks for your reply.

It smells of burnt diesel. The smell on shutdown happens while it is going through the shutdown procedure. And yes, the intake for the circulated air is close to both the intake for the combustion air filter and also the exhaust passes close to it as it heads to the exit thru-hull on the transom. (the whole system is in the aft locker) My first thought was that the exhaust was likely to be leaking and hence the circulatory air intake would suck it in and send it into the cabin, however I haven't been able to find a leak despite starting it up with my head in the cockpit locker brandishing a CO alarm. I may add a duct to the air intake so it draws air from within the cabin to keep the two systems completely separate, but in principle it shouldn't be necessary should it?

I haven't had the boat all that long - just six months - so I don't know if the system has always done this, but previous boats didn't seem to have the same issue.

It's not overwhelming, just a 30 second blast and not enough to trigger the CO alarm, but it does make the cabin smell and it clings to my clothes.

Grateful for any thoughts

Simon.
 
Some years ago my old Webasto started pumping air smelling of diesel exhaust into the cabin. On investigation it was found that the heat exchanger had corroded, thus the mixing of fresh air with burnt diesel gasses. (As the whole unit was already pretty old, I replaced it with a Planar/Autoterm equivalent.)

Perhaps you have something similar going on, albeit that the corrosion isn't so extensive and/or the mixing only happens on the startup/shutdown phases rather than when the system is running hot?
 
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Yes, that is what I was thinking/dreading/catastrophising about, although CO levels coming out of the vents seem ok. I'd like to get it checked out by an expert ideally.
 
Simon F said:
Hi,

Thanks for your reply.

It smells of burnt diesel. The smell on shutdown happens while it is going through the shutdown procedure. And yes, the intake for the circulated air is close to both the intake for the combustion air filter and also the exhaust passes close to it as it heads to the exit thru-hull on the transom. (the whole system is in the aft locker) My first thought was that the exhaust was likely to be leaking and hence the circulatory air intake would suck it in and send it into the cabin, however I haven't been able to find a leak despite starting it up with my head in the cockpit locker brandishing a CO alarm. I may add a duct to the air intake so it draws air from within the cabin to keep the two systems completely separate, but in principle it shouldn't be necessary should it?

I haven't had the boat all that long - just six months - so I don't know if the system has always done this, but previous boats didn't seem to have the same issue.

It's not overwhelming, just a 30 second blast and not enough to trigger the CO alarm, but it does make the cabin smell and it clings to my clothes.

Grateful for any thoughts

Simon.
Click to expand...

I did wonder if there could be fumes somehow escaping from the combustion air intake into the heating air intake due to something happening during shutdown. It shouldn't be that hard, I would have thought, to rig up a temporary (extended?) air intake from somewhere else nearby (even somewhere that wouldn't be practical long-term) for one or one or other of the combustion and heating circuits, which would confirm whether or not this was the issue.

If it does prove to be the problem you could then devise a permanant separation of the air intakes. Personally I wouldn't want to take the heating air intake from the cabin long-term, as this defeats the heating's rather valuable de-humidifying function (plus I like fresh air to breath!). But it's your boat, so do what suits you, but I do think it's worth establishing first whether the air intakes' proximity to one another is actually involved in the problem.
 
LittleSister said:
I did wonder if there could be fumes somehow escaping from the combustion air intake into the heating air intake due to something happening during shutdown. It shouldn't be that hard, I would have thought, to rig up a temporary (extended?) air intake from somewhere else nearby (even somewhere that wouldn't be practical long-term) for one or one or other of the combustion and heating circuits, which would confirm whether or not this was the issue.

If it does prove to be the problem you could then devise a permanant separation of the air intakes. Personally I wouldn't want to take the heating air intake from the cabin long-term, as this defeats the heating's rather valuable de-humidifying function (plus I like fresh air to breath!). But it's your boat, so do what suits you, but I do think it's worth establishing first whether the air intakes' proximity to one another is actually involved in the problem.
Click to expand...
Yes, I agree, it's a way to rule something out without needing to uninstall the system and courier it to Webasto (which may prove futile in any case if the installation is the problem rather than the heater.) I'll get on it and report back. Thanks Little Sister.
 
On my Eber this turned out to be the exhaust drain (which is necessary and safe!). On startup a single drip comes out (from the previous run) and evaporates on the hot metal, this is then drawn into the intake.
Found it by accident as happened to be in the locker plumbing when it started. Nothing that can sensibly be done about it other than routing the air intake elsewhere.
 
lustyd said:
On my Eber this turned out to be the exhaust drain (which is necessary and safe!). On startup a single drip comes out (from the previous run) and evaporates on the hot metal, this is then drawn into the intake.
Found it by accident as happened to be in the locker plumbing when it started. Nothing that can sensibly be done about it other than routing the air intake elsewhere.
Click to expand...
Said that. I am not sure about it being safe inside a boat, as I understand it the marine exhaust has no drain, only the automotive one is so made.
 
Boater Sam said:
Said that. I am not sure about it being safe inside a boat, as I understand it the marine exhaust has no drain, only the automotive one is so made.
Click to expand...
Most exhausts have a drain right next to the heater. It’s a safety feature to stop corrosion etc.
It’s safer than living next to a road with cars driving past. It’s mostly water.
 
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Simon F said:
Hello All,

When my Webasto Air Top Evo 40 starts up and when it shuts down, there's a smell of diesel in the cabin for about a minute. When it's running, it's fine. Even after hours of running it, there's no smell. It's mounted in the cockpit locker and the exhaust exits through the transom and seems sound. I've started it up while closely observing it and there doesn't seem to be a corresponding smell in the cockpit locker on startup or a big plume of exhaust smoke from the exhaust outlet in the transom, so my first theory, (that leaked exhaust was finding its way into the air intake) seems to be wrong. Surely there's no way the heater can generate the smell in the heat exchanger is there? It would happen constantly rather than just for a minute if that was what was happening wouldn't it?

I've experimented with holding the CO detector in the duct output in the cabin and in the cockpit locker but it hasn't tripped. I'm not keen on the smell and I'd get it looked at, but no one in Brighton seems to service or repair the heater.

Any thoughts?

Thanks

Simon
Click to expand...
Your CO detector is very unlikely to respond to diesel fumes providing your burn is stoiciometric ( complete and clean) as diesel, unlike petrol produces very little CO . ....Not saying do not have one.... Incomplete combustion will produce CO.
So always have a working detector
 
wingcommander said:
Your CO detector is very unlikely to respond to diesel fumes providing your burn is stoiciometric ( complete and clean) as diesel, unlike petrol produces very little CO . ....Not saying do not have one.... Incomplete combustion will produce CO.
So always have a working detector
Click to expand...
I have two. I remember the old days of gas water heaters.
 
lustyd said:
On my Eber this turned out to be the exhaust drain (which is necessary and safe!). On startup a single drip comes out (from the previous run) and evaporates on the hot metal, this is then drawn into the intake.
Found it by accident as happened to be in the locker plumbing when it started. Nothing that can sensibly be done about it other than routing the air intake elsewhere.
Click to expand...
Thanks. That is what I'll do.
 
lustyd said:
On my Eber this turned out to be the exhaust drain (which is necessary and safe!). On startup a single drip comes out (from the previous run) and evaporates on the hot metal, this is then drawn into the intake.
Found it by accident as happened to be in the locker plumbing when it started. Nothing that can sensibly be done about it other than routing the air intake elsewhere.
Click to expand...
None of my heaters have ever had a drain from the exhaust. That would be alright on a vehicle, but surely not in a boat.
 
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