Exhaust fumes when windows up and A/C on - non recirculate mode

[TCurtner]

That's an ACR-X catch can system with Arrow modified valve covers - that'd be the first place I'd check for exhaust fumes at this point.

would fumes be coming back through the breather? Or a leak in the 1/2" lines?

[Steve M]

Breather would be my guess, but it is certainly worth checking the lines...the catch can vents crankcase pressure, which consists of combustion blow-by (all the garbage that makes it past the piston rings), so it'll smell like exhaust. Aside from an actual exhaust leak, this is the next most likely culprit, especially since it vents under the hood.

[TCurtner]

Breather would be my guess, but it is certainly worth checking the lines...the catch can vents crankcase pressure, which consists of combustion blow-by (all the garbage that makes it past the piston rings), so it'll smell like exhaust. Aside from an actual exhaust leak, this is the next most likely culprit, especially since it vents under the hood.

I still haven't located it - i plan to attempt to completely seal that breather today, as going on a medium drive late today. will eliminate (or not) this as the culprit. After that, the exhaust sills :-(

Also: interesting aside on this puke can/breather setup. I attempted to drain the system, and just some dry junk fell out, a few grams probably...Being a racer, and having a system on that car, I expected some dark/nasty oil - at least a little. Nothing. is this normal??

[TCurtner]

My 2001 GTS did this, it was from an exhaust leak on my corsa exhaust. For some reason the clamps did not seal tight. I installed myself so took it to a muffler shop and they fixed it.

where are those clamps located? would it be similar place (anyone speak up) on the GenIV??

[MtnBiker]

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looks like breather system.

It's the catch can. I had this on my Gen IV after I installed the K&N catch can with breather.

[TCurtner]

It's the catch can. I had this on my Gen IV after I installed the K&N catch can with breather.

Is there a solution?? Maybe extend the breather to another position?

[Steve M]

Is there a solution?? Maybe extend the breather to another position?

You could potentially change it to a closed loop system, but you'll have to do some re-plumbing of the system.

[Roddy]

I don't think you want a closed loop system, due to increasing crank case pressure. I may be wrong on this, I'd have to check. I will also have to look at my breather set up. I have to say I'm not sure this is the issue, but if this is the fix, then holy crap... I have seen threads on this issue dating back to 2004 with no solutions found.

I also added in new HFC's over the winter which reduced the issue by 80% atleast so I'm wondering how that plays into things.

[Steve M]

I don't think you want a closed loop system, due to increasing crank case pressure. I may be wrong on this, I'd have to check. I will also have to look at my breather set up. I have to say I'm not sure this is the issue, but if this is the fix, then holy crap... I have seen threads on this issue dating back to 2004 with no solutions found.

I also added in new HFC's over the winter which reduced the issue by 80% atleast so I'm wondering how that plays into things.

When I say closed loop, I mean one line coming in to the can from the passenger side valve cover, and one line coming out of the can going back to the intake manifold, breather sealed off. For this to work properly, you'll need to come up with a solution for the PCV check valve that ends up getting removed when you run a can with a breather. You'll also need to reconnect the line that runs from the airbox to the driver's side valve cover (make-up air source). If you want to make sure that line never feeds oil into the intake, you'll need to run another catch can of some sort just on that line.

As described, it would retain the factory PCV routing and will not cause any issues. Simply capping off both vents most definitely would cause issues...I'd consider that a closed system (as opposed to closed loop).

[TCurtner]

***UPDATE***

Since this may have been related to exhaust, and since i've been looking for headers/cats/pipes anyway, i decided to put the solution off since i'd probably be pulling the side sills for the new exhaust, as one of the suggestions was to pull them and check for exhaust leaking/connections checking.

Well, the other day i was coming up long/slow driveway and the sun angle was just right to see the gases coming up out of the little filter on top of the catch can - through the hood vents. It was VERY apparent. So it makes sense that these gases get swept back into the HVAC intake when the car is in forward motion. I think by re-routing the catch can filter - probably extending it - to another outflow area - say out of the gills, i might be able to fix this issue. Will report back on success /failure and post some pics when i can.
Thanks for everyone's help on this.

[nautoncall]

I’m reviving this thread as I have the same problem. I have routed the catch can “fumes” to the driver side with hose and a breather but I can still smell it while sitting a couple minutes at a light. Also it’s not cool seeing some smoke fumes coming from under the hood vents at a light either. So aside from routing the breather back under the car, is there any harm in plumbing to the intake??

[Steve M]

I’m reviving this thread as I have the same problem. I have routed the catch can “fumes” to the driver side with hose and a breather but I can still smell it while sitting a couple minutes at a light. Also it’s not cool seeing some smoke fumes coming from under the hood vents at a light either. So aside from routing the breather back under the car, is there any harm in plumbing to the intake??

It's just a possible ingestion point for oil, but as long as you have a properly designed catch can, it shouldn't be much of an issue.

That said, you shouldn't use a catch can designed for a breather if you are going to be routing it back to the intake, which will be under vacuum. Here are the main differences in the two types of catch can systems you can run:

Open loop system: catch can will likely be hollow, and will have a breather on top. You route the PCV lines to the catch can, but do not return back to the intake manifold. The make up air line that runs from the air box (not under vacuum) to the driver's side valve cover needs to be removed, and both ends capped off. The PCV valve itself needs to be removed. This setup is the only 100% way to make sure no oil makes it back into the intake manifold. The drawbacks are that you can get fumes, and the crankcase is also not being vented by vacuum. This can potentially lead to oil contamination as the blow by gases are not being actively removed from the crankcase.

Closed loop system: catch can will have internal baffles to give the oil droplets a chance to condense and collect in the can. The PCV line from the passenger's side valve cover is routed in to the catch can, and the line coming out goes back to the intake manifold, which will be under vacuum. The catch can will likely have an inlet and an outlet that are not interchangeable (the gases are only intended to flow one way). The PCV valve needs to remain in place. This is intended to keep the system from pulling too much vacuum at idle - too much vacuum will pull oil back into the intake. This setup is the only 100% way to make sure you don't smell fumes; it also ensures that your crankcase blow by is adequately vented since it will be under vacuum. The drawback is that there will still be some amount of oil in the fumes that has not cooled enough to condense, so it will end up in the intake manifold. How much depends on the design of the catch can. I'd consider the amount to be negligible compared to the factory setup.

Bottom line: if you intend to change the system operation from vented (open loop) to closed loop, you'll need a different catch can, and you'll have to change the line routing. This is not hard, but is also not cheap.

[nautoncall]

It's just a possible ingestion point for oil, but as long as you have a properly designed catch can, it shouldn't be much of an issue.

That said, you shouldn't use a catch can designed for a breather if you are going to be routing it back to the intake, which will be under vacuum. Here are the main differences in the two types of catch can systems you can run:

Open loop system: catch can will likely be hollow, and will have a breather on top. You route the PCV lines to the catch can, but do not return back to the intake manifold. The make up air line that runs from the air box (not under vacuum) to the driver's side valve cover needs to be removed, and both ends capped off. The PCV valve itself needs to be removed. This setup is the only 100% way to make sure no oil makes it back into the intake manifold. The drawbacks are that you can get fumes, and the crankcase is also not being vented by vacuum. This can potentially lead to oil contamination as the blow by gases are not being actively removed from the crankcase.

Closed loop system: catch can will have internal baffles to give the oil droplets a chance to condense and collect in the can. The PCV line from the passenger's side valve cover is routed in to the catch can, and the line coming out goes back to the intake manifold, which will be under vacuum. The catch can will likely have an inlet and an outlet that are not interchangeable (the gases are only intended to flow one way). The PCV valve needs to remain in place. This is intended to keep the system from pulling too much vacuum at idle - too much vacuum will pull oil back into the intake. This setup is the only 100% way to make sure you don't smell fumes; it also ensures that your crankcase blow by is adequately vented since it will be under vacuum. The drawback is that there will still be some amount of oil in the fumes that has not cooled enough to condense, so it will end up in the intake manifold. How much depends on the design of the catch can. I'd consider the amount to be negligible compared to the factory setup.

Bottom line: if you intend to change the system operation from vented (open loop) to closed loop, you'll need a different catch can, and you'll have to change the line routing. This is not hard, but is also not cheap.

Steve, thanks. Makes sense. I thought it would then make it under vacuum so might create some issues. My car is TT so I was thinking of running a pipe to the intake between the filter and turbo.

Maybe just reroute further back will be the best.

Thanks again