Exhaust Fumes in cabin

[912s]

So far I've replaced the gaskets on the exhaust (head pipe and muffler, the muffler needs to be replaced as I can see a very small leak in one of the seams), installed new door seals that had been removed by the previous owner. Also found he wasn't very careful when installing the rear tunnel cover in the backseat. It only had a couple of screws that were too short and only went into the carpet. And since I don't drive it in the winter I have also sealed (can you say duct tape?) the air returns on both sides above the axles under the car. All of this has helped but.... still there, more noticeable at highway speeds than around town.

The engine has about 2500 miles on an overhaul so it's not like there's a trail of smoke or anything, more like I'm piping exhaust inside.

When I was rebuilding the accelerator linkage I noticed that the tunnel has a couple of large cutouts from the factory on the side and top near the front. The rear of the tunnel under the car is wide open. Is this suppose to be sealed somewhere between the front and rear to keep fumes out?

Anybody else had this problem? Any thoughts would certainly be appreciated.

Scot


’67 912 (with the windows down)
www.geocities.com/ford10n/

[josh912]

Same problem, still trying!

------------------
Joshua Harrison
1968 912 Coupe

[Ads912]

Hi. My name is Adam and my interior stinks too.
But seriously, I thought that it was just my car. I noticed it more with my old (leaky) exhaust system. The exhaust smell in my car is at it's strongest when the "go-pedal" is to the floor.
My engine was also just rebuilt, so that could be another reason why the smell is not as strong now.
There are 2 vent tubes that run from the rear window area to the engine compartment. I was wondering if fumes were coming in there?
Scot, the cutouts in the front of the centre tunnel in my car have covers held on with screws.



[This message has been edited by Ads912 (edited 06-06-2001).]

[markdam]

mine isnt on the road yet so i dont know about the fume prob. But adam or anybody can you elaborate on your venttubes mine wer piped with a foam hose that was /disinegrated
a: where do you get new hose
b: why a vent from the engine area to the cabin?
c:anything else anyone wants to add
thanks again

------------------
1966 bought 4/20/01
in progress......l..

[Efrain68912]

My guess is the heater boxes have rusted out. They are expensive and hard to find, so I am planning on replacing mine with Bursch J pipes. Much cheaper and I'm not sure anyone will miss that laughable system that Porsche refered to as a heating system.

[Ads912]

Markdam,
My foam tubes must be missing. All I have is a metal tube that runs from the engine compartment to the interior. It is 2 or 3 inches long.
I think that I am going to plug them.

Adam.

[912s]

The heater boxes aren't connected to anything, and the ducts that they connect to have been sealed which did help some.

Tonight I plugged the 2 vent tubes in the rear shelf area. That did help some as well. Does anybody know what these are suppose to be connected to? I would assume they are for suppling fresh air?

I'm still wondering about the tunnel. Above it was mentioned that there were covers on the forward access point(s). Mine however simply has carpet laid over without making any cutouts. Previous owner used some sort of spray adhesive to glue the carpet to the floor as well as kick panels etc. But even if the one on top had a cover fastened to it, the side where the accelerator linkage goes thru leaves a pretty big hole as well. Again this simply has carpet laid in there behind the pedal with a hole for the rod to pass thru to connect to the back of the pedal.

I think I might try and build a wall in the tunnel out of that expandable foam thru the rear access hole. If I wrap the shift tube with say wax paper... then the tube could still move freely and not destroy the seal?

Any other thoughts out there? Thanks again for the input.

Scot

’67 912(windows still down)
www.geocities.com/ford10n/

[Roland Kunz]

Hello

The 912 had two different heating systems. One was the "Freshair" exchangers and the others where the export exchangers.

The Freshairversion uses fresh air and heat them up in the exchangers.

The Export version are just some flaps that guides the colling air from the cylinder fins into the cabin.

The last version do allways smell like hot air from an engine. The freshairversions are a that better as long there is no oil in them.

To check if you have monoxide in the cabin use a tester.

The two isolation pipes in the engine bay are for the rear screen defrosting ducts.
The hoses are AFIR 22mm iD and Porsche still sale them. Only the isolation is NLA but simple to replicate.

Holes in the kickpanel are for the fuelline, electric looms, speedo, shifter, cables. The usally have rubber gromets or boots.

Open holes will vent the cabin and let more noise in.

Grüsse

[czach]

Ok, I can help here...

The two rear vents are supposed to go to the heat exchanger pipes just after the heat valves. They exist to defrost the rear window.

If they are connected to nothing, then they would be pulling air into the body from around the engine. IE: Exhaust. Bad.

The vent for the early 911/912's is actually just above the rear window on the back of the car on the outside. This is why you don't want to spray water UP on the rear window; the water will enter the vent and drip down your headliner.

Chris
68 911L


Chris


[QUOTE]Originally posted by 912s:
Tonight I plugged the 2 vent tubes in the rear shelf area. That did help some as well. Does anybody know what these are suppose to be connected to? I would assume they are for suppling fresh air?

[912s]

Problem solved!

The final problem was the tunnel. While looking yesterday to see where fumes could be
coming from I realized there wasn't any type of boot for the shift linkage where it exits
the rear of the tunnel. Temporarily to test I used some duct tape inside and expandable foam
outside to seal the end of the tunnel. it worked great, so then I went to the parts catalogs
to see what I could find, and found that there is a 2-piece (inner/outer) boot that belongs
there.

These parts can be found in the 911/912 Shift Linkage and Pedals section in Pelican's
Catalog under Shf Couple

Thanks for all the input

[josh912]

Glad to see you found the problem and solution BUT were are the exhaust fumes coming from. Sounds like you have an exhaust leak if there are fumes coming out somewhere besides the talepipe. With the engine running loisten and feel for exhaust leaks. You can feel puffs of air if there's a leak. Good Luck.

------------------
Joshua Harrison
1968 912 Coupe
www.geocities.com/jkh912

[912s]

No leaks that I can find, that was the first thing I checked replacing all of the gaskets, and going as far as wrapping the joints with that repair tape where the front/rear pipes connect (even though there wasn't any evidence of a leak).

Since the fumes weren't a problem until 60-65mph. I believe it's a simple matter of a vacuum being created and sucking the fumes from the engine compartment. The tailpipe exits just under the fender behind the left tire, which is probably fine at slower speeds, but when traveling faster a vacuum is created and draws the fumes back into the engine compartment... that is if there's no boot at the end of the tunnel which is how the vacuum is created.

At least that's my theory since plugging the tunnel solved the problem.

Scot

[Roland Kunz]

Hello

Now way for suking back the exhaustgases if driving at higher speeds.

If you have the flap exchangers then you can smell the engine gets hoter. Sometimes cleaning from the oilcooler and the cylinderfins give fresh air. Also check for any oil leaks.

Just like I said before; there is no exhaust fume in the cabin as long the J pipes have no crack. All the smell comes from the engine cooling and that is what all aircooled heating systems have to bear. Just keep the heat exchanger and the heatproducer as clean as possible and you only can smell the overheatet air.

Grüsse