Fumes in the cockpit problem

Calvani · 03-17-2005, 01:23 PM

Hi Folks,

Have any of you had problems with fumes getting into the cockpit of your 944?

I have made sure there are no abnormal oil leaks in the engine, and a smoke (leak) test of my exhaust system yielded negative results (note that the exhaust system is in excellent shape - no cracks etc..). I have also checked for any holes in the car/body/chassis (ie under the car or in the engine bay)...Yet, fumes do appear to be getting inside the car apparently through the a/c vents. This is usually very noticeable as the engine is just warming up (while driving and coming to a stop) or when I blip the engine. Note that the smell resembles more exhaust/burned oil than actual fuel smell.

Anyway, next, I intend to get a new seal/gasket for the rear of the engine bay. Since the one currently on the car is somewhat compressed in some areas (after so many years of usage).

Any comments or suggestions on what to try next to diagnose this problem?

Thanks very much in advance!

Humberto-

'86 944 NA, 156K
'01 Boxster 29k

AznDrgn · 03-17-2005, 01:29 PM

if you are sure it's coming through the vents most likely it's the gasket at the rear of the engine bay at the top of the firewall.

Calvani · 03-17-2005, 01:40 PM

Well, I am not 100% sure it is coming from the vents...But I cannot determine how else the fumes are making it inside the cabin. Note that I am noticing the fumes when the windows are closed.

Anyway, thanks for your response.

Cheers,

Humberto-

AznDrgn · 03-17-2005, 01:43 PM

Do you notice them more after you have filled up your gas tank? How did you check your exhaust for leaks?

Calvani · 03-17-2005, 01:55 PM

No, I have not noticed any correlation when there is more gas in the tank. Why do you ask?

I did not checked the exhaust for leaks myself. My mechanic used a smoke machine that was
connected by the tail pipe and pumps a special "smoke" back into the system. In this manner one can track if there are any exhaust leaks.

Humberto-

legion · 03-17-2005, 02:06 PM

There is a junction in the exhaust where the catalytic converter meets the muffler pipe that is just a few feet from the shifter knob. If you have a from where these two pipes meet, it could work its way in to the cabin through the hole for the shifter.

AznDrgn · 03-17-2005, 03:03 PM

Normally if it stinks more when you fill up the fuel tank filler hose is the culprit. An easy way to check your exhaust is to fire up the motor and then stuff a rag in the tail pipe so you build up a little back pressure. If you have a leak you'll hear it hissing or if you have a weak point it might blow it out. Don't do this for more than a few seconds at a time.

SoCal Driver · SoCal Driver's Garage

Pull the tail lights and replace the tar like gasket. Also check your hatch seal.

If the gasket on the top of the fire wall is good (that is it seats against the hood) and the gaskets for the AC and heater hoses are good then most exhaust comes in from the back of the car.

Calvani · 03-17-2005, 05:51 PM

Thanks very much, guys...

I will try both suggestions and let you know what I find.

Humberto-

ike229 · 03-17-2005, 09:23 PM

I have a very similar problem, and it seems to be worse when my fuel tank is full. I have heard that it could be the charcoal canister, but will check my fuel tank filler line when i get a chance.

VINMAN · 03-18-2005, 05:52 AM

Are you talking about gasoline fumes, or exhaust fumes?

SoCal Driver · SoCal Driver's Garage

Fresh gasoline fumes after a fill up are from the gas tank and/or related fittings. The newer gas tanks are plastic a tend to crack on the top. Also the filler and vent hoses tend to come loose. As the cab has a negative pressure any spillage or loose vent hose will fume the interior. You can pull the slanted cover on the passengers side and inspect the filler and most of the vent hoses. Also pulling the cover over the gas level sender will let you see some of the top of the tank. Other wise you have to drop the tank.

Calvani · 03-18-2005, 07:48 AM

Guys, I think you solved the problem for me!

I went to check the hatch seal and noticed that is in good condition. *But*, upon closer examination, I noticed that the hatch itself does not FULLY close, but leaves a very thin but yet large enough gap for the fumes to make it inside the car. After the re-adjusting the cone-screws in the locks, the problem appears to have been solved....!

I am just surprised that I was not hearing any vibrations from not a fully closed hatch...Anyway, the problem is solved...Thanks again for the feedback.

It's amazing how something so apparently minor was creating such a big problem.

Cheers,

Humberto-