joseph mitro

my heater mostly blows hot - i know it's not the little cheap plastic piece under the dash because i've already checked. but also, the vents almost always (but not 100% of the time) blow exhaust fumes into the cabin. the headers were welded last year when they were off, so i don't think there is a header problem.

i plan to eventually turn this car into a track car, meaning i probably won't need the blower motor, but am wondering if you guys have any suggestions on where to start looking for this exhaust smell in the cabin. gets annoying after a while, and my wife doesn't like it either.

SoCal Driver

Since the intake for the fresh air blower is just in front of the hood it is supposed to take in the air off of the wind shield area.

There is a seal across the fire wall seperating this area from the engine. If the seal is bad or missing or if the hood is not sitting square you will get engine nasties sucked into the fresh air intake.

TKS

are you sure it's coming in through the vents? Could it be the rear hatch seal?

Magown

Joseph, I spent a lot of time dealing with exhaust smell in my 944's. I've found that the generic fixes ie, replacing the rear hatch seal and making sure the rubber boot under the leather **** boot is attached doesn't always do the job.

Give me some more feed back as to the conditions that you smell it in your car. Like windows open, sunroof open, a/c fan on, a/c snow flake on etc...

joseph mitro

TKS - I'm pretty sure it's not coming through the rear hatch. Magown - there is no specific time it comes in. I have tried driving with the air recirculation button on and off, and it seems to come in whether or not the recirculation button is active. also, i haven't used the snowflake a/c button since buying the car since the a/c doesn't work. the exhaust smell happens whether or not the windows or sunroof are open. the rubber boot under the shifter is attached - i installed a new leather shift boot and attached everything correctly within the last few months.

I may check on the seal across the firewall connecting to the fresh air blower - that sounds reasonable

RobbyK

This problem is notorious for 944’s that sat for along time then started getting driven regularly, most of the time it is just something you have to deal with and let go cause the cause is rarely found, other times, if there are no cracks in the exhaust, it goes away on its own.

Cyrus951

Mine gives the same smell. It makes me dizzy after a couple of minutes.
I believe it's the catalyis that the PO replaced himself. I don't think he did a good job welding it back on.

Also, that black plastic cover that covers the fresh air blower on my car is all cracked and missing pieces. How much are those black plastic covers?
Could the cracks in the cover be causing the fumes under the hood to come into the cabin?

SoCal Driver

Check that the tail lights are sealed to the body.

Yabo

hey,thought this might be a time to ask, because Magown had mentioned knowing something about such things.. mine gets exhaust smell if i open say, only the driver door window just a couple inches. Or if i hit high rpms i seem tog et a whif of exhaust. i know i have a chunk out of my rear hatch seal. But, why is it only smelling under normal driving when i open driver window...?

Cyrus951

zehnd

I had exhaust smell as well. I replaced the hatch seal and plugged the sunroof drains, didn't help.

But there was a hole in the bottom of my spare tire wheel well, I plugged that and it worked for me. Go figure.

Cyrus951

All my fumes seem to be coming from the front, I just drove it to try and pinpoint the problem, and the fumes seem to be coming from near the vents. Little help?

Yabo

hmm i got that hole in the wheel well ( i just noticed today). i thought it was plugged. guess not. what can i plug it with? duct tape or something?

zehnd

I had a plastic cap around the same size. I used a rubber adhesive to glue it on.

Magown

I’ve dealt with 5 944’s that have had the exhaust fumes in the cabin problem. It will really **** you off too. Every time you drive the thing you get out reeking of fumes. One thing that I noticed that they all had in common was that they only would suck in the fumes was when there was a vacuum condition in the cabin. What can create a vacuum in the cabin?

Vacuum Conditions:
Windows open
sunroof open
a/c &/or reticulate button pushed (if either of the buttons are pushed the recirculation flaps should be closed)

Common leak spots and reasons:
Rear hatch seal – I guess it’s possible for these to leak around the edges, but most of the time there is a gap in the center rear. The reason there’s a gap is because the person who installed it either didn’t want to take the time to put it on in one piece or didn’t think it would go on in one piece, so they cut it. There’s enough material to smash the two ends of the cut gasket together when new. As it ages it starts to shrink and the gap forms. This is an easy fix, simply replace the gasket. It takes 10 minutes to cut it and replace it, and 15 minutes to do it with out cutting.

Shift boot – this one shouldn’t be a problem if your exhaust system is leak free, but just about every run of the mill 944 & 951 I run across has some kind of an exhaust leaks. It’s an easy fix as it is normally just not seated around the lip on the shift tunnel correctly, however sometimes it’s torn from age.

DME wiring harness firewall grommet – If the two above methods do not work, this is the next place I look. It’s not uncommon for people to push this grommet aside so they can run boost controller hoses, wiring for gauges etc…around it. I’ve also seen some torn. The problem is the intake for the re-circulated air is located on the other side of the hole in the interior; it sucks any fumes that may come from leaks in the exhaust manifolds right into the fan and blows them right in your face. It will also suck from this area too with the windows down. If this boot is torn, there’s not much you can do, I don’t think they are available and to replace it would he a hassle, cause it is connected to a rubber sleeve that contains the wiring harness. Your best bet is to use some kind of sealant on it.

Rubber fan box isolation strip – I’ve never thought about this one, it’s a good idea. I’d rule it out on all the cars I’ve dealt with since they only sucked in the fumes when the cockpit was under a slight vacuum. If this thing was bad you would have fumes coming in when ever the a/c or re-circulate button is off. (I’ve always thought it was odd that the flaps shut when ever the a/c snow flake button is pushed, you would think they would only close with the re-circulate button. It’s been that way on the last 4 944’s I’ve owned, so I guess that’s how it’s supposed to work).


Holes in rear cubbies – not sure about these, I guess they could let exhaust leak in but it would probably take a big leak in the muffler

If anyone else has any other ideas or fixes I’d love to know them.