Exhaust coming into cabin when windows open

[Nate Dog]

But not when they are closed, so can only guess the airflow is generating a turbulence that sucks it in.. BUT FROM WHERE!!!???!!!

To date,
I have replaced the exhaust from the resonator back (doesn't appear to be leaking from anywhere), there was a crack in the boot, welded that up. 2 of the spare wheel well pugs were missing, replaced them. The rubber boot on the bottom of the gear shift lever under the car was missing, replaced that. The rubber seal around the boot looks to be in good condition, no tears and is pretty meaty/chunky.
Next thinking of replacing the flanges around the header pipes... but can't see/smell anything there anyway.

I'm tearing my hair out, its a maddening issue
Thats a lie, i have no hair, but i digress.

Could it be getting sucked in through the black plastic vents on the rear quarter panels?
Should i be plugging them up or are they that important?
With windows closed its fine, but as soon as you open the windows, well, lets just say it makes breathing inside the cabin rather... interesting...

Is this a common problem?

Any ideas?
Getting a little despondent.

[DomenicC1]

Hi Nate Dog,
I am no expert...so this is just my opinion from past experiences!

The smell can't be coming in from the rear plastic vents because if it was you would be getting the smell when windows closed and you mentioned you only smell it when window is down. Besides you have seemed to have gone through the necessities of plugging up any possible air leaks into the cabin. So I would say you are correct in saying that it's getting sucked in like a vacuum effect or whatever you want to call it.

I've had this happen to me in 2 previous Alfa's I have owned. An Alfa 75 and my previous 82 GTV. The 75 was partly due to a leak from the O2 sensor on the exhaust so fixed that but only fixed the smell marginally but was certainly noticeable.

Although, in my case and I'm not saying this is the case for you but unfortunately for me both times it was due to the fact that both engines were basically stuffed and burning oil out through the rear of the exhaust and getting sucked in like a vacuum effect when I rolled the windows down.

My current 83 GTV has no problem at all and no smell in cabin with windows down or up! If your car smells rich excessively when stationary at idle then I would say you have found your problem. Either it is burning fuel too rich or burning oil!

Again not saying this is the case with your GTV but this was my experience!

Regards
Domenic

[AikenDrum105]

I had a similar issue with my old gtv6  (and every 105 I've owned)     with the windows down you get a venturi effect sucking air from the cabin - pulling it back in wherever it can - the rear vents,  the gear lever boot,  and most importantly - through the stuffed rear hatch seals,  tailight seals,  spare wheel well bung,  bungs in the underfloor...     

I just used masking tape to seal the rear hatch closed to see if that was my leak - problem mostly went away...

the GTV6 also has a one way valve in the back around the fuel tank somehwhere - part of the charcoal canister recirc piping - supposed to let air in but not gases out..  the one way valve gets stuck open and lets nastiness into the cabin as well..     I'm pretty sure theres a good post on the alfabb on how to check that valve is ok and fix it if not..   could never smell it with cabin closed, but with sunroof or windows open - the lower pressure int he cabin was sucking the nasties in through the dud valve. 

I hope that helps a little  !

Cheers

[aggie57]

Is the exhaust standard?  Particularly the tailpipe?  Just if its shorter than standard then maybe its not clearing the body fully?

[bteoh]

I think it's a common problem as my GTV6 does that too.  I have always wondered why Alfa made the stock exit tail pipe kinked to the left far most corner of the rear bumper.

[Nate Dog]

Much much research later, leaving many things to check

No, exhaust not standard, kincks up not down, is well clear of the rear (half the damn reason i replaced the damn thing was the smell, well the noise was horrible but that effing smell).

Need to go through the whole boot and check for any ANY holes gaps cracks.
Need to check a valve on some kind of draw back air intake system that cycles through some sort of charcoal filter.

Need to find the Alfa engineers that designed cars that couldn't be driven with the windows open (Appears to be a very common problem, without many solutions, certainly no wholistic ones anyway) and cave their heads in...

Not happy. Was hopping for an awesome cool sexy car thats compromise didn't involve carbon monoxide poisoning.


Any and all suggestions are welcome and will be tried. Short of tarring myself and throwing a box of feathers up into the air..

[DomenicC1]

Hi Nate,

Is the car fumey out of the exhaust at idle when stationary. With my cars it was so bad that you couldn't stand around the car when it was idling cause it was burning oil. Or your car may be burning a little rich and if it's is smelly while at idle, it may only be burning rich and a simple tune or overhaul of the carbs might suffice...it you're lucky!

But this does seem to be a common problem with old Alfa's but there must be a problem somewhere as I said my current 83 GTV doesn't have this problem and it still has the original motor with very good compression and no excessive smelly fumes out of the exhaust. Still has all the original seals on doors, boot etc, and they're not in the greatest of condition and still no smell in the cabin.

A compression test will tell you if the rings are stuffed. Checking the charcoal canister will be a good idea. I am aware of it but never knew it could be responsible for letting fumes into the cabin. I have seen posts on it before, good idea to do some research on it first so you understand how it works...keep us posted!

Regards

[DomenicC1]

Check out the threads about charcoal canisters, just type 'charcoal canister' in search engine at right of screen, plenty of info there about it...good luck!

[aggie57]

Maybe not the message wanted but I'd try putting a downwards facing tip on the tailpipe.  Alfa did it for a reason....

[Beatle]

Nate,

Are you sure it's exhaust fumes? 

As you've just had the exhaust replaced I'm assuming there are no leaks (block the tailpipe to check).

It could be overfuelling and the smell is emanating from the engine bay (I had an occurrence where the air filter element got soaked in fuel and a backfire caught the paper alight!!!) .

Does it have the stock airbox (I think you said elsewhere it had pod filters?). 

Check the EGR as it may be blocked and/or feeding fumes into the engine bay.

If the sealing strip is missing from the body flange at the trailing edge of the bonnet, any engine bay fumes will feed straight into the vent plenum at the base of the windscreen and into the cabin.

Any gaping rust holes between engine bay and top of the firewall?  Stick your head in the engine bay and look rearward, up behind the triangular bonnet stop support panels.

Also check for holes in the firewall, missing grommets etc.  There is a plastic fitting which supports the vent plenum drain hose and these are often long gone, so allow engine bay fumes into the vent plenum, and into the cabin.

Check the charcoal canister recirc system.  I believe the Australian ADR setup is unique, so be wary of information/diagrams sourced from overseas.  If this is faulty it's more likely to smell of raw fuel though, not so much burnt exhaust gas.

The rubber diaphragm around the base of the gearlever intact?  Not the boot connected to the console you can see from the drivers seat, but the diaphragm sealing off the transmission tunnel.  If this is torn it will suck fumes and heat into the cabin with a window down.

Strip out the boot lining and make sure there are no holes or missing grommets.  Check the tail lights are sealed to the body.   Any holes in the spare wheel well?

It sounds like a stretch, but if you have a larger diameter exhaust pipe, the exhaust gas exit velocity can be slowed quite considerably, so a short straight tailpipe may not jettison the gasses fast enough to prevent recirculation back around the beaver tail.   Of course, this is only a problem if the exhaust is particularly fumey from oil or fuel. 

If you are used to newer catalysed cars, any old Alfa will be quite smelly/fumey. If the valve stem seals or rings are tired, it will be quite bad.  Do you see smoke in the rear view when planting your foot after a long period of trailing throttle, say on a long downhill run?

Is it possible that it's oil dripping onto the exhaust, and not actually exhaust gasses causing the smell?   Oil on the exhaust can be like blood from your kids nose or forehead.  A little goes a LOOOOOONG way   

[Beatle]

Taping up the rear hatch is a pretty good idea for troubleshooting.  The factory hatch seals have inserts positioned at the front corners to force the front of the hatch up, and therefore the rear of the hatch down and square onto the sealing rubber.  It also helps the hatch to 'pop' up an inch or so when you release the catch.

Even with good runners, if these solid inserts are missing, or have migrated (they are free to move inside the hatch seal) then the trailing edge of the hatch may not be squeezing against the rubber.  Worn hinges make it worse.

[Beatle]

Yours is a plastic bumper car, so has a plastic section over the vent plenum across the base of the windscreen?   

Probably not relavent to your car, but on the early cars there is an insignificant looking rubber strip attached to the lower windscreen metal trim.  This rubber has a dramatic effect on the vent system.  If it's missing, you can actually get reverse airflow from the cabin vents.  So that area is particularly sensitive when it comes to aerodynamics at moderate speeds.  If your vent cover is modified, that may be contributing to the fume problem.

i'm really grabbing at straws now.....................   

[Nate Dog]

Diaphragm at the bottom of the gear lever replaced as was missing all together, one of the first things i did. Definitely smelling exhaust not petrol, however, won't discount it being burnt oil. Not dripping on headers, was, but i replaced the rocker cover gasket to stop this about 3 weeks ago.

Breather from the top of the engine is piped using an aftermarket setup back into the air box, looks pretty tight. Am putting a catch can in anyway but its all there. will take the opportunity to run new hoses just in case it is pumping from there.

Carbs definitely need a tune, Yep, its smokey under load, white not blue, running very rich, and, theres fuel being pumped/leaking back through the carbs into the airbox, not much but enough so you can smell fuel when lifting the hood. It is on the to do list, as its not a fuel smell thats coming into the cabin i discounted that as the cause of my problems. Will go to top of the list of things to do then if you guys think it'll be causing the smell. But its definitely an exhaust smell and not a fuel one.

Like i said, will try all of the above.
Didn't see any noticeable holes in firewall, this is an amazingly rust free example, the only rust i had was on the surface panels. Will give it a thorough inspection tonight and see if there are any holes.
Will keep plugging away at it.

Want to get crackin on aircon but this takes priority.

[martym00se72]

What Paul said about a leaky rear hatch seal rings true for me. One of the rubber stoppers had perished and shrunk, making the hatch not sit square. I fixed that up and the exhaust smell disappeared. The idea of taping up the hatch might be worth it to see if that is the cause.
Happy hunting!

[Al Campbell]

+1 for the strip sealing bonnet in front of windscreen - temp tape to check.
+1 for boot seal - tape will check.

The old "Trans-axle" website (I think) detailed how the exit point of the original exhaust was critical to stop fumes getting in t the cabin when everything was new. Just something else to check for.