Strong sulphur smell in TD5 ventilation system

[akula]

Any ideas what could be causing a strong sulphur smell coming through the air vents?

It's been happening for around 2 weeks now.

I searched for this and a previous post suggested in cabin battery to blame - I don't have this though.

Any ideas?

[Toxic_Avenger]

Too many eggs in the diet?

[bee utey]

Heater core leaking coolant.

[bblaze]

you havnt by chance changed your brand of windscreen washer solution, only seen it a couple of times but it can be a problem
cheers
blaze

[akula]

Heater core leaking coolant.

How do I check this? I don't know where that is located.

[bee utey]

How do I check this? I don't know where that is located.

The heater core is located inside the heater box, under an acre of dash plastic and surrounded by dozens of electrical connections. Traditional methods of dealing with heater core leaks is to 1. disconnect the coolant hoses under the bonnet and loop them away from the heater, 2. put some radiator stop leak into the system. 3. replace the core at vast expense and effort or 4. put up with it until it explodes and dumps a load of hot coolant into the cabin. Not many modern vehicles are designed to be easily fixed, so it's something to annoy people who drive them way after their designed in use-by date.

[PhilipA]

Dead mouse. In heater fan?
regards Philip A

[Pippin]

Exhaust gas????

[trout1105]

Exhaust gas????

I was thinking that as well, Does the smell usually show up during or after heavy acceleration ?

[AndrewMilne]

How do I check this? I don't know where that is located.

Hi Akula,
The heater matrix (or core, like a small radiator) is located behind the dash panel (roughly in the centre), inside the passenger compartment.
Hoses come from the engine bay, through the firewall, to connect with the heater matrix.

To establish whether your smell is due to leakage from the heater core, I think a couple of things are worth checking.

1. Monitor coolant level in the radiator expansion tank. If the heater core is leaking, then the level should be going down (but it might only be slow, so far).

2. Put your head down into the front passenger footwell and driver's footwell, and use a small torch look for any sign of dampness and odour above the hump in the middle.

3. Have you noticed a gurgling sound coming from behind the dash-panel, inside the passenger compartment? This is a symptom of heater-core leakage.

If the cause of the smell is exhaust gas, then the exhaust manifold or pipe must be leaking, and you could probably hear this when the engine is running with the bonnet up. You could get someone to place a folded rag over the rear end of the exhaust pipe for a few seconds, and see if there is a hissing sound that would indicate a leak. I think such a leak would need to be in the engine bay for it to result in smell coming through the air-vents, so an exhaust leak much further back is probably not the culprit.

PhillipA's suggestion of a dead mouse is quite a real possibility.
The blower motor for the ventilation system is behind and under the glove-box.
If you remove it, anything that is in the pipe that brings air into the cabin from an intake under the plenum cover at the bottom of the windscreen may drop out. If not, but there is a bad smell from the blower, the blower needs to be opened!

bblaze's offering about windscreen-washer fluid/additive reminds me that I have sometimes experienced a noticeable odour in the cabin immediately after using the windscreen washers. It might be worth using the washers for a few seconds while you are driving, and seeing if you notice any smell that correlates with doing so. The intake for cabin air is located in front of and below the passenger's-side windscreen, just under the black panel that runs along the bottom of the windscreen. Water that drains off the windscreen can easily run underneath that black cover ("plenum"), into drains that carry it to either side. Without going down the air-intake pipe, the washer-fluid might impart an odour to the air being drawn in over it.
IF WATER DOES GO DOWN THAT AIR-INTAKE it will DEFINITELY show up on the carpet in the passenger's footwell (so long as there is enough of it).

Good luck,
Andrew

[akula]

I was thinking that as well, Does the smell usually show up during or after heavy acceleration ?

Not that I have noticed.

[akula]

Hi Akula,
The heater matrix (or core, like a small radiator) is located behind the dash panel (roughly in the centre), inside the passenger compartment.
Hoses come from the engine bay, through the firewall, to connect with the heater matrix.

To establish whether your smell is due to leakage from the heater core, I think a couple of things are worth checking.

1. Monitor coolant level in the radiator expansion tank. If the heater core is leaking, then the level should be going down (but it might only be slow, so far).

2. Put your head down into the front passenger footwell and driver's footwell, and use a small torch look for any sign of dampness and odour above the hump in the middle.

3. Have you noticed a gurgling sound coming from behind the dash-panel, inside the passenger compartment? This is a symptom of heater-core leakage.

If the cause of the smell is exhaust gas, then the exhaust manifold or pipe must be leaking, and you could probably hear this when the engine is running with the bonnet up. You could get someone to place a folded rag over the rear end of the exhaust pipe for a few seconds, and see if there is a hissing sound that would indicate a leak. I think such a leak would need to be in the engine bay for it to result in smell coming through the air-vents, so an exhaust leak much further back is probably not the culprit.

PhillipA's suggestion of a dead mouse is quite a real possibility.
The blower motor for the ventilation system is behind and under the glove-box.
If you remove it, anything that is in the pipe that brings air into the cabin from an intake under the plenum cover at the bottom of the windscreen may drop out. If not, but there is a bad smell from the blower, the blower needs to be opened!

bblaze's offering about windscreen-washer fluid/additive reminds me that I have sometimes experienced a noticeable odour in the cabin immediately after using the windscreen washers. It might be worth using the washers for a few seconds while you are driving, and seeing if you notice any smell that correlates with doing so. The intake for cabin air is located in front of and below the passenger's-side windscreen, just under the black panel that runs along the bottom of the windscreen. Water that drains off the windscreen can easily run underneath that black cover ("plenum"), into drains that carry it to either side. Without going down the air-intake pipe, the washer-fluid might impart an odour to the air being drawn in over it.
IF WATER DOES GO DOWN THAT AIR-INTAKE it will DEFINITELY show up on the carpet in the passenger's footwell (so long as there is enough of it).

Good luck,
Andrew


Thanks for the comprehensive post! I will look into this on weekend. I will update what I find.

[akula]

Too many eggs in the diet?

Or my heater is possessed by satan....

[akula]

The heater core is located inside the heater box, under an acre of dash plastic and surrounded by dozens of electrical connections. Traditional methods of dealing with heater core leaks is to 1. disconnect the coolant hoses under the bonnet and loop them away from the heater, 2. put some radiator stop leak into the system. 3. replace the core at vast expense and effort or 4. put up with it until it explodes and dumps a load of hot coolant into the cabin. Not many modern vehicles are designed to be easily fixed, so it's something to annoy people who drive them way after their designed in use-by date.

Good times!

[rick130]

Gear oil ? (ie. via the front diff or t/case breathers and the ubiquitous cracked pelnum)

[bob10]

This is one of the most fascinating problems I think I have seen on the forum. I'm really interested to see what it is.

[rick130]

Jut asking, but your name isn't Beelzebub by any chance ?
Or maybe the D2 has become a portal or hellmouth ? [bigwhistle]

[trout1105]

Maybe the kids in the back are being sneaky and are playing with matches [biggrin]

[Bohica]

The only source of sulphur that I can think of is the battery, and that is in the sulphuric acid. Is it more of a rotten egg smell?

[trout1105]

I noticed that cars with catalytic converters tend to stink like rotten eggs when they are passing on the road.
I don't know if this is confined to petrol engines and not diesels But I did notice it when cars first started to be fitted with cat converters.
That's why I asked if the smell was associated with acceleration
.

[Tins]

I take it you aren't constantly following a new car around?

[trout1105]

I take it you aren't constantly following a new car around?

No Mate, I usually get a whiff as they overtake me [bigwhistle]

[akula]

The only source of sulphur that I can think of is the battery, and that is in the sulphuric acid. Is it more of a rotten egg smell?

Yes, like rotten eggs.

[akula]

I noticed that cars with catalytic converters tend to stink like rotten eggs when they are passing on the road.
I don't know if this is confined to petrol engines and not diesels But I did notice it when cars first started to be fitted with cat converters.
That's why I asked if the smell was associated with acceleration
.

I am pretty sure there's no catalytic converter in my car.

It's intermittent and stays for up to 15 mins, and if anything I notice it most when idling, possibly due to reduced airflow through the HVAC?

I am hoping it's just something dead in the HVAC system, I don't know how that would be intermittent though.

[Bohica]

Yes, like rotten eggs.
Overcharging of a battery can produce hydrogen sulphide ie rotten egg gas.
Can you check the charging?

[akula]

Overcharging of a battery can produce hydrogen sulphide ie rotten egg gas.
Can you check the charging?

I am crap with electronic stuff, how do you do that? My Nanocom gives batt volts I think.

I also have a duel battery system to confuse the matter.

[AndrewMilne]

Hi Akula,

I don't agree with Bohica that overcharging a battery will produce Hydrogen Sulphide.
I think it will produce both Hydrogen and Oxygen (at alternating plates within the battery).
Both of those gasses are odourless, so they simply cannot be the source of your smell.
I think that Tim Sanderson (Traxide Electronics) would know the answer to this, so it might pay to ask him (he's on this forum quite often).

As far as a catalytic converter is concerned, if your TD5 has one it is located roughly under the passenger-side floor, too far back to make a smell that would be likely to be drawn into the cabin air-intake. Especially while the car is in forward motion.

If you really want to check out the battery-overcharging idea, I suggest that you take the car to an auto-electrician, and ask him to tell you whether or not that is actually happening. If it's not, then it just doesn't have anything to do with your issue.

Cheers, Andrew

[thai_tiger]

thought I remember reading same problem a while back.... might be the same


bad smell (https://www.aulro.com/afvb/discovery-2-a/247302-bad-smell.html)

[Bohica]

Hi Akula,

I don't agree with Bohica that overcharging a battery will produce Hydrogen Sulphide.
I think it will produce both Hydrogen and Oxygen (at alternating plates within the battery).
Both of those gasses are odourless, so they simply cannot be the source of your smell.
I think that Tim Sanderson (Traxide Electronics) would know the answer to this, so it might pay to ask him (he's on this forum quite often).

As far as a catalytic converter is concerned, if your TD5 has one it is located roughly under the passenger-side floor, too far back to make a smell that would be likely to be drawn into the cabin air-intake. Especially while the car is in forward motion.

If you really want to check out the battery-overcharging idea, I suggest that you take the car to an auto-electrician, and ask him to tell you whether or not that is actually happening. If it's not, then it just doesn't have anything to do with your issue.

Cheers, Andrew



You have your opinion and I have science. Overcharging a battery can produce H2S. Google it. [emoji2]

[Pippin]

A few weeks ago I had the EGR blanking plate gasket on the manifold leak, no noise but the smell through the vents was very sulphurous. If it is diesel exhaust gas it is very dangerous on a long trip, I know from experience.
Nick

[Roverlord off road spares]

You have your opinion and I have science. Overcharging a battery can produce H2S. Google it. [emoji2]
found this googling also mentions smell from battery.

Rotten Egg or Sulfur Smell Coming from Diesel Exhaust by Robert Moore
Diesel exhaust has always had a significant smell compared to the smell of a gasoline engine's exhaust, but in general it shouldn’t exhibit much of a sulfurous smell. A sulfur or rotten egg smell is exactly that, the presence of hydrogen sulfide in the exhaust system. There are a number of causes for the rotten egg smell you are experiencing, including a source of stench that may not even have anything to do with the exhaust or engine at all.

A Bit More About Diesel Diesel fuel is often referred to as diesel oil because it is refined from crude oil, just like gasoline. Interestingly enough, diesel produces more energy than gasoline at 147,000 BTU per gallon as opposed to gasoline's 125,000 BTU. There is always going to be a certain amount of sulfur in diesel fuel, which depends largely on the quality of the crude oil it was made from. The different companies that produce diesel fuel are bound to certain specifications; however, the amount of sulfur in any given company's diesel fuel will vary.


Types of Diesel There are two different types of diesel; Basic diesel and ULSD, or ultra low sulfur diesel. Regular diesel can have up to 5000 parts per million of sulfur to be legally sold within the United States, as to where ULSD-rated diesel can have a maximum of 15 parts per million. Technically, there are three different grades of diesel fuel rated for use with diesel engines: No. 1-D S15, or ULSD, which is rated at a maximum of 15 PPM, No.1-D S500 can have a maximum of 500 PPM and NO.1-D S5000, which can have a maximum rating of 5000 PPM.



Sulfur Smell in Exhaust There are a couple of things than can cause a sulfur smell to be emitted with your exhaust gases. The first of which depends on the quality of the fuel available from your local gas station. If your gas station supplies the lowest grade of diesel, there could be up to 5000 PPM in sulfur content, which could cause a light-to-moderate sulfur or rotten egg smell in your exhaust. Pay attention to the grade of fuel you purchase, as a ULSD-grade diesel fuel -- noted on the pump -- has a lower sulfur content. ULSD-grade fuel can often be found at more popular or brand name gas stations. The only other likely cause for the sulfur smell, barring fuel quality, is either too much fuel being wasted and burning off in the catalytic converter or a clogged catalytic converter that releases too much sulfur. However, your vehicle may not be equipped with a catalytic converter, since diesel engines release lower amounts of noxious gases compared to gasoline. If your vehcile has a catalytic converter and ULSD grade fuel doesn’t solve your problem, you should probably look into replacing the converter.


The Battery Often a noticeable sulfur smell in the cab can be confused for a rotten egg smell in the exhaust. The only thing under the hood that will likely emit a sulfur smell would be your battery or batteries, depending on your vehicle's set up. This will involve looking into your alternator or generator's performance, as well as the voltage and amperage it should be supplying. An alternator that is faulty or has a bad external regulator could be overcharging the battery, causing the electrolytic fluid inside to boil; which in turn creates a sulfur smell. Let your engine idle for a while and inspect your battery. If there is fluid escaping the caps on the top of the battery, your charging system probably has a fault that needs to be diagnosed and repaired immediately. Keep in mind that an over charged battery poses the risk of a potentially deadly explosion, making it a good idea to wear safety glasses and fire-proof clothing when inspecting the battery and charging system.




ALSO SOME OPINIONS ON A DIESEL FORUM, On battery over charging,
Rotten Egg Smell! - TheDieselPage.com Forums (http://www.thedieselpageforums.com/tdpforum/showthread.php't=33056)

[AndrewMilne]

You have your opinion and I have science. Overcharging a battery can produce H2S. Google it. [emoji2]
Hi Bohica,

Concerning your first sentence, I think much the same, but which of us may be correct isn't really the main point here.

In my previous post on this, I went on to suggest that Akula get the battery charge-rate tested, to establish whether or not it is too high.
If the battery is not being overcharged, then this becomes a total non-issue in the actual context of the discussion, because (even if you're right), there would not be any Hydrogen Sulphide being produced by overcharging.

Agreed?

Cheers,
Andrew Milne

[Tins]

I take it you aren't constantly following a new car around?

This was tongue in cheek, but it leads me to ask: have you checked the exhaust manifold for the dreaded warping causing the studs to undo and the gasket to leak? Or, as Pippin says, the EGR? A leak, combined with a higher sulphur content fuel could be the issue. The intermittent bit could simply be caused by you fuelling up somewhere else from time to time, or forward motion blowing the leaked gas away from the vent intake.

Just a guess, like all the others.

[AndrewMilne]

I am crap with electronic stuff, how do you do that? My Nanocom gives batt volts I think.

I also have a duel battery system to confuse the matter.

Hi Akula,

your mention of having a dual battery could be relevant to the smell you experience in the cabin.

If one of your batteries is located close to the turbo-charger, it is likely to get very hot, resulting in accelerated loss of electrolyte and general deterioration.
That could be a source of sulphurous odour.

AND: this position is very close to the air-intake for the cabin ventilation.

IF the second battery isnext to the turbo, what about lifting the bonnet when the engine is at normal operating temp, leaning over and sniffing near the battery? Also checking the electrolyte level, if it is a battery where that can be done.

I suggest wearing safety goggles for this.

Cheers,
Andrew

[Roverlord off road spares]

I take it you aren't constantly following a new car around?

I do recall I used to hate having the VP-VN commodores pass me, they stunk big time. Maybe that's the reason people called them dunnydores?

[Tins]

I do recall I used to hate having the VP-VN commodores pass me, they stunk big time. Maybe that's the reason people called them dunnydores?

VLs were the worst. What was surprising was that Nissan could build that ( rather good ) 3.0 litre engine in a Skyline without the smell, but Holden couldn't do it in the Commodore.

[bob10]

Some good advice here. From what I've read, the good money would have to be on the overcharged battery. Assuming the exhaust system is free of leaks, but surely you would hear these. However, if your battery is totally sealed, what then ? Checking the battery charge is probably the first step, I'd suggest.

[rangieman]

found this googling also mentions smell from battery.

Rotten Egg or Sulfur Smell Coming from Diesel Exhaust

by Robert Moore
Diesel exhaust has always had a significant smell compared to the smell of a gasoline engine's exhaust, but in general it shouldn’t exhibit much of a sulfurous smell. A sulfur or rotten egg smell is exactly that, the presence of hydrogen sulfide in the exhaust system. There are a number of causes for the rotten egg smell you are experiencing, including a source of stench that may not even have anything to do with the exhaust or engine at all.

A Bit More About Diesel

Diesel fuel is often referred to as diesel oil because it is refined from crude oil, just like gasoline. Interestingly enough, diesel produces more energy than gasoline at 147,000 BTU per gallon as opposed to gasoline's 125,000 BTU. There is always going to be a certain amount of sulfur in diesel fuel, which depends largely on the quality of the crude oil it was made from. The different companies that produce diesel fuel are bound to certain specifications; however, the amount of sulfur in any given company's diesel fuel will vary.


Types of Diesel

There are two different types of diesel; Basic diesel and ULSD, or ultra low sulfur diesel. Regular diesel can have up to 5000 parts per million of sulfur to be legally sold within the United States, as to where ULSD-rated diesel can have a maximum of 15 parts per million. Technically, there are three different grades of diesel fuel rated for use with diesel engines: No. 1-D S15, or ULSD, which is rated at a maximum of 15 PPM, No.1-D S500 can have a maximum of 500 PPM and NO.1-D S5000, which can have a maximum rating of 5000 PPM.



Sulfur Smell in Exhaust

There are a couple of things than can cause a sulfur smell to be emitted with your exhaust gases. The first of which depends on the quality of the fuel available from your local gas station. If your gas station supplies the lowest grade of diesel, there could be up to 5000 PPM in sulfur content, which could cause a light-to-moderate sulfur or rotten egg smell in your exhaust. Pay attention to the grade of fuel you purchase, as a ULSD-grade diesel fuel -- noted on the pump -- has a lower sulfur content. ULSD-grade fuel can often be found at more popular or brand name gas stations. The only other likely cause for the sulfur smell, barring fuel quality, is either too much fuel being wasted and burning off in the catalytic converter or a clogged catalytic converter that releases too much sulfur. However, your vehicle may not be equipped with a catalytic converter, since diesel engines release lower amounts of noxious gases compared to gasoline. If your vehcile has a catalytic converter and ULSD grade fuel doesn’t solve your problem, you should probably look into replacing the converter.


The Battery

Often a noticeable sulfur smell in the cab can be confused for a rotten egg smell in the exhaust. The only thing under the hood that will likely emit a sulfur smell would be your battery or batteries, depending on your vehicle's set up. This will involve looking into your alternator or generator's performance, as well as the voltage and amperage it should be supplying. An alternator that is faulty or has a bad external regulator could be overcharging the battery, causing the electrolytic fluid inside to boil; which in turn creates a sulfur smell. Let your engine idle for a while and inspect your battery. If there is fluid escaping the caps on the top of the battery, your charging system probably has a fault that needs to be diagnosed and repaired immediately. Keep in mind that an over charged battery poses the risk of a potentially deadly explosion, making it a good idea to wear safety glasses and fire-proof clothing when inspecting the battery and charging system.




ALSO SOME OPINIONS ON A DIESEL FORUM, On battery over charging,
Rotten Egg Smell! - TheDieselPage.com Forums (http://www.thedieselpageforums.com/tdpforum/showthread.php't=33056)
Well done Mario
Google and Science in the same post[bigrolf]

[rangieman]

Some good advice here. From what I've read, the good money would have to be on the overcharged battery. Assuming the exhaust system is free of leaks, but surely you would hear these. However, if your battery is totally sealed, what then ? Checking the battery charge is probably the first step, I'd suggest.
Battery totally sealed no wet cell battery is totally sealed[wink11]
See Science and Google is your friend[bigwhistle]
Battery ventilation is vital (http://caravanandmotorhomebooks.com/battery-ventilation-is-vital/)

[bob10]

Good link. Put into my favourites, peruse later. From what I read, sealed batteries will produce h2, not h2s, dangerous if not ventilated, but doesn't solve this sulphur smell problem.

[Tins]

Some good advice here. From what I've read, the good money would have to be on the overcharged battery. Assuming the exhaust system is free of leaks, but surely you would hear these.

Not arguing, but I never heard mine. People outside did, though, as it got worse. I could see them looking.

Disclaimer: ([bigrolf]) I recently got hearing aids...

[Toxic_Avenger]

Did somebody say Science?!


An interesting property of H2S is olfactory Fatigue.
It's an annoyance in low concentrations (can be smelt as low as 0.008ppm), and respiratory complaints at much higher concentrations around 10ppm. Deadly at approx 500ppm.

The interesting part is where you lose the ability to smell it as exposure increases with time. The threshold is approx 100ppm.
Here's a case (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850187/) of a poor bugger who copped a solid lung-full after welding inside a tank used to store sulfur products in an oil refinery. Almost died. (I'm hoping to have my 'solid lung-full' accepted by the International System of Units... watch this space!)

This article (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550088/pdf/13181_2009_Article_BF03160912.pdf) discusses further the aetiology, and clinical signs of H2S poisoning.
H2S affects Cytochrome C oxidase, a mitochondrial protein that is used in the oxidative phosphorylation process, which converts ADP to ATP- one of the chemical 'fuels' our body uses. Cyanide also affects this same protein.

Don't be alarmed though... the low levels needed to smell H2S are a long way from something that will kill you.
H2S is an interesting gas.

[Bohica]

[QUOTE=Toxic_Avenger;2699283]Did somebody say Science?!

Yes

http://ehs.whoi.edu/ehs/occsafety/leadAcidprocedure.pdf

Near the end of para 4 on page 3 we have the smoking (battery) gun
• Over-charging a lead-acid battery can produce hydrogen-sulfide, which is colorless, very poisonous,flammable, and has the odor of rotten eggs.

Check the battery(s)

[akula]

Thanks for all the replies about this!

Well after the problem seemingly went away over use over weekend it was back this afternoon. Opened the bonnet and the smell very strong around the aux battery. I checked the volts to main and aux battery a bit later on (no smell at that time though) both steady at around 12-14 volts (couldn't get exact as it was dark). Nanocom said ~13.85 to 14.05 volts - which are pretty normal readings.

So what should I do now?

Take out affected battery?

[akula]

Did somebody say Science?!


An interesting property of H2S is olfactory Fatigue.
It's an annoyance in low concentrations (can be smelt as low as 0.008ppm), and respiratory complaints at much higher concentrations around 10ppm. Deadly at approx 500ppm.

The interesting part is where you lose the ability to smell it as exposure increases with time. The threshold is approx 100ppm.
Here's a case (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850187/) of a poor bugger who copped a solid lung-full after welding inside a tank used to store sulfur products in an oil refinery. Almost died. (I'm hoping to have my 'solid lung-full' accepted by the International System of Units... watch this space!)

This article (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550088/pdf/13181_2009_Article_BF03160912.pdf) discusses further the aetiology, and clinical signs of H2S poisoning.
H2S affects Cytochrome C oxidase, a mitochondrial protein that is used in the oxidative phosphorylation process, which converts ADP to ATP- one of the chemical 'fuels' our body uses. Cyanide also affects this same protein.

Don't be alarmed though... the low levels needed to smell H2S are a long way from something that will kill you.
H2S is an interesting gas.

Thanks for busting out the science Mitch!

126859

[bob10]

Thanks for all the replies about this!

Well after the problem seemingly went away over use over weekend it was back this afternoon. Opened the bonnet and the smell very strong around the aux battery. I checked the volts to main and aux battery a bit later on (no smell at that time though) both steady at around 12-14 volts (couldn't get exact as it was dark). Nanocom said ~13.85 to 14.05 volts - which are pretty normal readings.

So what should I do now?

Take out affected battery?

Process of elimination, I guess. Try it and see. How old is that Battery?

[akula]

Process of elimination, I guess. Try it and see. How old is that Battery?

2+ years old at least, was in it when I bought the car.
I topped it up about 3 weeks ago.

[discorevy]

I topped it up about 3 weeks ago.

Bingo, overfilled maybe?

[akula]

Bingo, overfilled maybe?

That's quite possible.
But why now and not back when I did this?
And why intermittently?

[Toxic_Avenger]

I think having to top it up is a symptom of the problem, not the cause.

[discorevy]

That's quite possible.
But why now and not back when I did this?
And why intermittently?

Possibly because back when you did it ,topping up would have flattened the battery, then after a good run giving it a charge it will bubble , if overfilled it would bubble out, and being ( I'm assuming) near the turbo would give a Strong sulphurous smell

[bee utey]

If the battery has one crook cell the other cells in series would overcharge and gas vigorously. Take it out and measure its terminal voltage after 12 hours with a multi meter and see how it is. I would recycle any battery that has bad smells in an otherwise normal electrical system.

[bob10]

By jove, Holmes, I think we have it!. The game is afoot.

[akula]

No sulphur smells on today's commute (~160 klms) following disconnecting aux battery.

Now onto the next issue....good times 😥

[bob10]

To quote the great Sherlock Holmes, in the " adventure of the Engineers thumb " , " Each new discovery furnishes a step which leads on to the complete truth ". Pardon the pun, for he who puns would pick a pocket. [bighmmm]

[rodg]

Had this problem in my disco 3 and discovered that the vent tube for the battery had dislodged and smell coming through the vents.
Cheers Rodg[smilebigeye]