Exhaust fumes

[Derek364]

Hi,

When stationery the aircon is sucking in fumes. If I isolate the aircon to the cabin or if the car is travelling then no problem. This happens even if there are no cars in front so it is self generated. Anyone had a similar problem?

[MarkyM]

Sounds like either your exhaust manifold (directl under the engine has a leak/crack

If it were a break in the intake manifold/breather you certainly wouldn't get exhaust fumes.

Easiest way to check is with a warm engine to partially block the exhaust pipes with some rag and put your nose under the bonnet from the side and see if you smell anything. Safer alternative is to have an emissions check done.


If it's the smell of fuel (as oposed to exhaust fumes) it may be a cracked intake manifold near the fuel rail or else a bad breather on the top of the petrol tank which is alloing escape into the cabin from th rear.

I can't remember if the XK8 has a carbon canister/cabin filter (on previous cars a poorly operating or faulty one can lead to fmes) and can't find my JTIS disc at the mo.

Is the smell evident without the ventilation on (if yes then think fuel breather) if not then look to the other causes.

Sorry I can't be of more help.

Mark

[Derek364]

Thanks for the pointers Mark. The car rececently had an MOT and it was doing this prior to that - would the emissions test for the MOT have picked this up.

It only happens when the aircon is on - if i operate the fan without the aircon then so far no problems or if the aircon is on and the fan is high don't appear to get any problems. - Its a carbon smell not petrol and coming through the front vents.

[Derek364]

Maybe I'll get a new cabin filter to start with as this is the cheapest cause to eliminate. - I would imagine they are relatively easy to replace.

[MarkyM]

Derek, yep an MOT emissions test would may hav noticed that your figures (from the probes stuck in your zausts) were low...but that wouldn't be a fail since less fumes would have been reaching the sensor probes and it would have produced more favourable emissions.

Excepting of course they were gassing you!

Mark

[Derek364]

I'm just a bit puzzled why it only happens when the aircon button is on - does the aircon draw air from a different part of the engine?

BTW, Mark, I have purchased the JTIS disc that you referred to - about $20 from ebay (including shipping from US).

[mike020150]

Just a thought. Aircon can suffer from bugs growing in the system. These microbes have been known to create strange smells. I believe it's possible to have such systems treated with bactericides to kill the little blighters although I don't have personal experience of the issue. Mike.

[Derek364]

Mike - looking on the internet there are various inexpensive products available to de-odourise/ de-bug the air con. So as soon as the JTIS disc arrives I am going to to change the cabin filter and buy one of these sprays and take it from there. - Thanks.