Rotten egg smell
 

Hi!

I have 2010 XC70 D5 (with 151kw) and for a month, once in a while, there is an intensive smell of sulphur/rotten eggs in the cabin. Battery seems good, no indication that it has failed. Engine works good - no loss of power or anything.
Local independent shop had a look, didn't see anything out of ordinary, used a odour bomb and cleaned the vents, but after a day, the smell came back. I asked them if it could be the catalytic converter that has failed, but they said that if any of the fumes from the catalytic converter were to enter the interior, there should be a hole in the cars bottom but there is none. Smell isn't permanent, it comes and goes, about once in a day, depending on how often I drive.

Vida doesn't show anything, no codes related to emissions or anything.
Has anybody had any experience with this kind of problem? What to look out for, how to troubleshoot?

Only other rotten egg smell is diff oil.

Or the screenwash reservoir which is a popular culprit

just wondering if a small rodent has curled up somewhere and given up. Smell comes as cabin warms up? Carpet wet in footwells?

Rotten egg smell is often Hydrogen Sulphide, which is a chemical byproduct of decomposition. This could come from stagnant water, rotting rodent, leaves or debris.

H2S is detectable by smell at very low concentrations, but at higher concentrations is extremely harmful and potentially deadly. It also affects the sense of smell, so your observation of briefly smelling it is slightly concerning. Are you just getting a whiff each day, or is the concentration numbing your sense of smell and harming you?

Worth getting it checked. Have a good look anywhere that water, rodents or leaves can collect. My mother once had mice nesting in the heater box and only detected when they chewed through alarm wires causing a small fire.

Thanks everybody!

All good information.
Guys at the workshop looked for any dead animals, didn't find any. Cabin filter was replaced 2 months ago by myself and the mechanics checked that place also - nothing out of ordinary. I'm going to check the windscreen washer system - although I topped it up few weeks ago, the nozzles do seem to be a bit clogged, maybe there is something up with that.

About the smell intensity - the sulphuric smell is not always there. If I sit in the car in the morning, I can't smell it but it comes up suddenly while driving. Sometimes I haven't noticed any regularities with it but I'm trying to. It seems that you get use to it and after a while it doesn't smell so intense. I'll keep you updated if I find anything.

Transmission and rear diff fluids were changed about 35000 miles ago. So another change/flush is my plans but hard to believe that the issue is there, but who knows.

have they checked the alarm battery is not leaking.

If the smell comes up suddenly while you are driving then perhaps it is coming in through the ventilation system. If so, then it could be a smell being generated outside the passenger compartment and drawn in by the fan.

Don't assume the smell is your car as it may be entering from the environment.

My car had an intermittent issue of smelling bad a few years back then realised it was the smell of the local rubbish landfill when the wind was blowing a certain direction.

The most obvious cause of rotten egg smell, as mentioned above, is from outside, and the culprit is usually other cars’ catalytic converters when they are cold. Certainly used to be the case, but less so now, maybe your following a smelly car. Next time you go out, set the air to recirculate and then see.