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Cabin fumes

D

Dunners

New member
As per the title"¦

It's been an issue ever since I got the car and has got to the point where I hate driving it now because of it. With Summer fast approaching and a road trip around Scotland at the end of May it's going to forever piss me off unless I find a solution.

Don't get me wrong, it's not horrifically bad to the point where I'm choking or can't drive the car "" but every time I open the side window a quarter of the way down I get the occasion smell of fumes in the cabin. With just the sun roof open I don't get anything at all or if I have both windows open nearly full (obviously).

I'm fully aware that the issue lies with the 944's aerodynamics, and how the car creates a positive pressure at the rear when driving along. Then, when the windows are open it creates a negative pressure in the cabin and sucks it in (I may have got that bit the wrong way round, but you get the idea).

Any advice would be greatly appreciated if you've come up against this issue and managed to find a solution. The car has been to Pro Max and Olly at RPM. It seems to be a common problem having searched extensively online and I've collated a list of where the issue may lie.

So far I've changed the hatch seal, tail light seals and sealed up any hole I could find with transparent sealant or gaffa tape! Basically I've run out of holes to fill"¦ The seal between the rear glass and frame looks fine, plus I get no water leaks whatsoever. I've replaced my pins at the back with new items and made sure the locking catches are well greased. When the boot is closed there is no movement whatsoever when pressed down. The flaps over the petrol tank that are situated below the rear carpet have been filled with sealant as well, as again, this supposedly can cause an issue.

The only item I haven't checked is the gaiter seal along the transmission tunnel. The gaiter was replaced by the previous owner, however I just can't see how the hell that amount of smell would be able to penetrate through!?

Any suggestions at all would be greatly appreciated!

Many thanks.


Drew
 
I dont get any fumes inside my car when driving with the windows down or the sunroof open, I know some people do but I have not noticed it in either of my Porsches 924S or 944S2. Might be worth checking the exhaust to see if it is leaking at any of the joints.
 
I had this on my car and eventually traced it to one of the exhaust manifold => down pipe gaskets.

Edited to add:

Another 'weak point' (if that is a fair description after 20+ years) seems to be the weld joint between the pipe and the forward face of the rear silencer box.
 
You said:
The only item I haven't checked is the gaiter seal along the transmission tunnel. The gaiter was replaced by the previous owner, however I just can't see how the hell that amount of smell would be able to penetrate through!?
Click to expand...

Have you looked under the new gaiter? There should be another rubber gaiter under the leather one which is what does the sealing.... and the new gaiter could be hiding a split sealing gaiter.
HTH
 

ORIGINAL: Jonny944CS

I had this on my car and eventually traced it to one of the exhaust manifold => down pipe gaskets.

Edited to add:

Another 'weak point' (if that is a fair description after 20+ years) seems to be the weld joint between the pipe and the forward face of the rear silencer box.
Click to expand...


Both Andy at Promax and Olly at RPM checked the exhaust and found nothing untoward. If it were the manifold/down pipe surely it wouldn't matter if the windows are open or not as it would flow from the front of the car through the cabin vents? It also happens when I have the 'air re-circulation' button pressed, which is meant to stop air from the outside getting in is it not?



ORIGINAL: sr.944man

You said:
The only item I haven't checked is the gaiter seal along the transmission tunnel. The gaiter was replaced by the previous owner, however I just can't see how the hell that amount of smell would be able to penetrate through!?
Click to expand...

Have you looked under the new gaiter? There should be another rubber gaiter under the leather one which is what does the sealing.... and the new gaiter could be hiding a split sealing gaiter.
HTH
Click to expand...

No I haven't checked yet - I just can't see how the amount of fumes I smell would get through. The new gaiter and surrounding plastics are so tight I have no idea how it would be getting through even if the seal below is buggered. Also, surely if fumes were getting through from that area constantly they would infuse an oily/petrol smell into the transmission carpet that covers that area, for which there isn't.

The moment I open the window the smell always seems to initially come from behind me which obviously leans to something I've missed in the back. The previous owner had got rid of most of the sound deadening and rear seats. Is there any seals/holes that I may have missed do you think?

Thanks for the replies chaps.

 
Hi Greg, I could always smell a certain degree of petrol in the car and don't remember it getting any worse after I removed the sound deadening, although I think there may well be some holes in the shell (factory) under where the rear seat was? I agree it was pretty unbearable at times but also knew it was a common trait so just put up with and didn't breath onto any naked flames after a long journey[:-]
 
Hi Ben,

Greg? Haha. First time I've been called that.

Regarding the holes - I've plugged everything I could see with tape.

The only thing I can see that might cause an issue is where the roll cage has been installed. Did you install this yourself? Are there any holes behind the metal panels at the bottom that you know of - maybe holes that were drilled but never lined up and therefore had to be drilled again?


Drew

 
Sorry Drew! Was on the phone and typing at the same time! Doh! Yeah I installed the roll cage, it fits into the bolts for the rear seat belts, so there was no drilling and therefore no exposed holes. I always wondered if there were some fuel vapours seeping out of the funnel from the filler into the tank when there was no carpet in the car, but it didn't get any better when I put the carpet back in so thought it couldn't be that?
 
The fuel smells have gone - it was the lids where you can gain access to the top of the fuel tank that had been opened and not sealed back properly. It's always fumes I get, and I can't bloody figure out where they're coming from! :)

I've replaced everything that I've read online that can cause the issue bar the gaiter... When you changed this can you remember the state of the rubber gasket that was situated below as mentioned above?





 
Have I read it properly - you get exhaust fumes (not petrol) coming into the cabin whwn you crack open a window?

If so, its the rear hatch seal.
 
I have exactly the same problem with my car, I have only had it 5 minutes so I am reading all the posts and learning about these great cars.

A new hatch seal for me then, sorry to hijack the thread.
 
Could it be that the car is running incredibly rich?

It may be that there is no more or less leakage than any other car, but your exhaust is putting out excess fumes. Have you tried someone following you in another car?

 

ORIGINAL: Diver944

Could it be that the car is running incredibly rich?

It may be that there is no more or less leakage than any other car, but your exhaust is putting out excess fumes. Have you tried someone following you in another car?
Click to expand...


I hope not! The car was over fueling when I first bought it.

ProMax checked the AFR and got it running correctly after a long search but Andy did report he found nothing particularly wrong.

It's been like this since day one really. There was a point where the fumes got a lot better (probably me just not opening the windows over the winter period)... however I just seem to notice it a lot more now the weather is improving.

My Dad has followed the car recently when it's been driven hard. He said he smelt nothing strange and saw no black smoke coming out the back which would lean towards unburnt fuel.







 

I would go check what Mike said .. Rear hatch seal and the hatch pins are notorious for this. If the hatch dosent close right then the fumes get sucked into the cabin !

My CO was that bad at a stage that the car smelled like an RUC Landrover.. The hatch pins were worn and it would have brought tears to your eyes [:D] Got the CO sorted and a new set of hatch pins and hatch seal - Sorted
 
ORIGINAL: A9XXC

Have I read it properly - you get exhaust fumes (not petrol) coming into the cabin whwn you crack open a window?

If so, its the rear hatch seal.
Click to expand...

ORIGINAL: VanhireBoys

I would go check what Mike said .. Rear hatch seal and the hatch pins are notorious for this. If the hatch dosent close right then the fumes get sucked into the cabin !

My CO was that bad at a stage that the car smelled like an RUC Landrover.. The hatch pins were worn and it would have brought tears to your eyes [:D] Got the CO sorted and a new set of hatch pins and hatch seal - Sorted
Click to expand...


Sorry chaps - maybe I wasn't clear.

Both these items have been replaced.

So far I've changed the hatch seal, tail light seals and sealed up any hole I could find with transparent sealant or gaffa tape! Basically I've run out of holes to fill"¦ The seal between the rear glass and frame looks fine, plus I get no water leaks whatsoever. I've replaced my pins at the back with new items and made sure the locking catches are well greased. When the boot is closed there is no movement whatsoever when pressed down. The flaps over the petrol tank that are situated below the rear carpet have been filled with sealant as well, as again, this supposedly can cause an issue.
Click to expand...

Everything I've ever read about cabin fumes and it's possible cause has been replaced bar the gaiter.

I was hoping for a possible other solution that someone may have come across?




 
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