My '96 Sable (180K miles) started, probably about 10K miles ago, smelling (intermittently) in the cabin when I have the vent fan on, regardless of whether the temp is set cool or warm. It smells like exhaust or something burnt. It will smell for a few minutes, then the smell seems to go away for awhile, then it comes back. I recently changed the air cabin filter but that did not help. Any ideas?

 

you could have an exhaust leak at the headers, the catalytic converter or the air injection system (if equipped). spray a little dish soap and water mix on a COLD engine and start it up. if you see bubbles forming on seams or bolt on places. If there's a heat shield to protect hands from touching the exhaust manifold, you'll have to remove that so you can see. if there's no visible leaks from the top side, it may be where the catalytic converter bolts to the exhaust manifold. If that's not it either, your catalytic converter may be going bad and you're just catching whiffs of the blow back from the tail-pipe when you slow down or stop. If you have an air injection system, check it for leaks too. I had a massive leak pop up on my 88 Grand Marquis when the check valve that went from the diverter valve to the cats blew out (probably when my muffler detonated - that was an interesting day). The diverter valve melted quickly and I didn't discover it for a few days. I had exhaust pumping directly into the engine bay. I don't think there's that kind of smog pump and air injection system on the sable, but I'm not real up on those cars either so I'm giving you everything to look for.

 

Appreciate the note, Slymer - this sounds thorough - again, what baffles me is the intermittent nature of it all - about 20% of the time I smell it, 80% I don't. So, to narrow it down, based on what you said and I think I know about the engine - catalytic converter, or where catalytic converter bolts on to the exhaust manifold, or headers. I don't think these have an air injection system or smog pump. I'm not a real car guy - interests are more with motorcycles.

 

Does it smell like exhaust or just something burning in general? Have you taken notice if HVAC or blower settings make a difference?? An intermittent exhaust smell could be related to whether the HVAC system is recirculating the cabin air, or pulling in fresh air.. If it's more like something burning, and blower speed changes it, it could be an ailing blower moter resistor, or motor itself...

 

The heating and cooling of metals(expand and contract) could cause the intermittent odors.

 

im gonna say exhaust leak...

 

I think the exahust leak might be the leading candidate after a call to the mechanic I use (who has been pretty reliable in the past). I just wanted to get some opinions in advance so that I would have some things for him to look at. To answer MaxFax3's question - definitely not a burning smell - more exhaust-ey, to coin an adjective. The heating and expansion of joined parts is an interesting angle on it. Thanks all -

 

could be a broken or leaking EGR tube or pipe. also check PCV valve or crankcase hose, or loose or missing oil cap (could possibly be smelling crankcase vapors)

 

The. oil filler cap is an interesting idea. Jiffy Lube put the thing on so tight a few months ago that I had a lot of trouble getting it off. Since then I've intentionally kept it a bit loose. Am traveling this week - will check it out when I return.