Jump to content
Ultimate Subaru Message Board

how does exhaust get inside car? blowby?


Recommended Posts

my car has always stunk like there was exhaust getting in somehow. I haven't been able to tell any difference between when the vents are on or not either. Smell goes away when the car is moving and I do mostly highway driving, so it's been more of a nuisance than anything so far.

 

We had the first real cold (well, in the 20's I guess) moring here. I started the car and let it warm up while blasting the defrost to clear up the windshield. After 10 mins or so I got in to drive to work and the interior of the car was very smoky and full of exhaust. A couple blocks driving with the windows down and I could breath again, but why was it so bad that morning?

 

It hasn't happened since, but then, it hasn't been quite as cold either. I'm not at all familiar with the ventilation/climate control system, so I have no where the vents draw air from or what might be happening. I know the engine has significant blowby and there is palpable air movement from the oil filler tube. Is there some way that the blowby exhaust could find its way through the vents?

 

While I'm on the subject...do you think its better to have the oil filler cap sealed tight? or loose so the exhaust has an escape? I was thinking I could force the blowby back through the PCV to contain it, but then I decided it would be better to leave the cap loose enough to provide the pressure with an easy escape.

Link to comment
Share on other sites

Outside air is drawn into the car through the grille at the bottom of the windshield.

 

Try running the system on "recirculate". If exhaust fumes still get into the car, you've probably got rusted out wheel wells or a rust hole somewhere in the trunk.

 

The oil filler cap is supposed to be air tight. If your car won't run right unless the oil filler cap is loose, you may have a plugged crankcase ventilation hose. These hoses get stiff with age and accumulated deposits.

Link to comment
Share on other sites

Not sure on your car, but on the BRATs, the air intake is about dead center in front of you, in the wiper cowl, as you're setting in the passenger seat. Quite possible that the blow-by fumes are being sucked in there. Check the rubber seal along the top of the firewall, it should seal against the hood when shut, to help eliminate that problem.

 

As for the PCV system, sounds like the hoses, and/or the engine covers are blocked with crud. These things happen.. Would pull all of the hoses off, clean them out. Maybe even pull the cam covers off and do them too. Unless your rings are totally shot, you shouldn't get a lot of blow-by out of the oil fill cap otherwise.

Link to comment
Share on other sites

do you have an exhaust leak, that would be my first guess. just having a leak below you will be enough to be annoying. an exhaust leak below the floorboard can also leak through bolt holes that hold the seats in place on some vehicles. those bolts may be rusted, stripped and have enough play in them to allow some fumes to enter the car.

Link to comment
Share on other sites

Exhaust (as we all know) is a bad thing in the cabin. I'd start by looking on the exhaust system start to finish for a leak. You'd sure smell/feel/hear it quick under the car. That's most likely the source and the first thing to fix. After that I'd look at how it got inside the car. Although once you find the source that may tell the answer on how/where it got in.

 

Just stating the stupid...because that's what I know the most about!:lol:

Glenn

82 SubaruHummer

01 Forester

Link to comment
Share on other sites

I've just taken my 2004 Forester to the dealer to ask this very question. They told me that using low octane fuel allows too much junk to burn in the catalytic converter, producing more exhaust and allowing it to seep in through the vent above the converter anytime the car is not recirculating interior air. (Using the defroster, for example, requires you to use outside air). So I'll try to use 89 octane fuel in the winter at least and see how it goes, but Subaru really needs to find an alternative solution to this. It is unbearable. And, while I really do like my Forester, don't get me started on the steel wheels and mag chloride...

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...