Air blowing into the cabin, cant figure this out

white99c2 · 03-20-2010, 03:54 PM

I went to replace a dash light in the speedometer for the brights indicator and while I was driving last night I noticed it wasn't working so I popped out the speedo and played around with it. Got it to work just fine but as I was cruising along in my neighborhood I felt cold spring ait blowing out of the hole that the speedometer goes into.
Today I removed everything from the front trunk trying to determine where this air is coming from and I cannot locate the source.
Here is my concern, in AZ the summer 115 degree air is coming in as well. After the speedo is seated the air stops however I do feel a constant steady cool spring air flow coming from the defroster and A/C vent, it is not strong but I can feel it.
I blocked the air intake in front of windshield as well as checked the hood/trunk seal for leaks, I'm stuck, where else would air be getting into the trunk as I'm driving, the faster I go the faster it blows, like RAM AIR coming out of the speedo hole.

ossiblue · 03-20-2010, 04:19 PM

Every 911 I've had allowed some air into the trunk--it is not an air tight seal. When you sealed off the air intake in the cowl, did you completely cover the screened area? or did you just stuff something into the air inlet? I ask because there is a foam seal around the air inlet to the fresh air fan which will let air (and water) into the area behind the gauges.

You should not be getting air through the defrost vents unless the hoses/tubes which connect the blower to the diverters is not connected or the flapper inside the outlet to the blower is bad--assuming you have all the levers on the dash controls all the way to the left.

With the cardboard cover over the blower and rear of the instruments, along with a carpet snapped over the cover, the air flow is reduced, but not eliminated completely. You can try a new trunk seal and adjusting the closed position of the trunk, but if all seals are good, you'll still likely get some air intrusion at higher speeds.

white99c2 · 03-20-2010, 05:05 PM

Thank for the reply. I used blue painting masking tape to cover the entire air inlet and was still getting air out of the defroster vents. The cardboard cover is intact, I removed it and sprayed it with a fresh coat of semi-black while it was off. I checked and lubricated both of the dampers mechanisms while I had the cardboard off, they slide easily and seat all the way. The blower motor is burnt out, if I slide the dash control to the right pleanty of air volume flows when the car is moving, Slide it to the left and an ever so slight breeze is still coming in. My concern is: maybe thats why I could never get vent temps below 60 degrees last summer when it was 115 in the day time. If the cabin has hot air blowing into it the A/C will struggle. It was 72 here today and I got 36 degree vent temps.

What do I do to block up the air flow?

Jerome74911S · 03-20-2010, 05:11 PM

Quote:

Originally Posted by ossiblue

Every 911 I've had allowed some air into the trunk--it is not an air tight seal. When you sealed off the air intake in the cowl, did you completely cover the screened area? or did you just stuff something into the air inlet? I ask because there is a foam seal around the air inlet to the fresh air fan which will let air (and water) into the area behind the gauges.

You should not be getting air through the defrost vents unless the hoses/tubes which connect the blower to the diverters is not connected or the flapper inside the outlet to the blower is bad--assuming you have all the levers on the dash controls all the way to the left.

With the cardboard cover over the blower and rear of the instruments, along with a carpet snapped over the cover, the air flow is reduced, but not eliminated completely. You can try a new trunk seal and adjusting the closed position of the trunk, but if all seals are good, you'll still likely get some air intrusion at higher speeds.

Yikes! Does this mean that water gets into the trunk, too? I'm new to my Porsche and have only driven it in very light rain, so I haven't seen water in the trunk. However, since the speaker grille on the dashboard no longer contains a speaker, cold air blows in through it. Is this the same situation as air through the speedometer hole? There is a lot of air and the rubber seals around the trunk lid don't look that bad.

Jerome

pete3799 · pete3799's Garage

The dampers have a foam rubber seal around them that disinagrate over time.
Mine was shot ( euro's only have one flapper installed) I made a new one.
This may be the source of your air leak.

white99c2 · 03-20-2010, 05:26 PM

No rain into the trunk, just air coming in. What about the air flow coming in behind the instrumentation. Its like a fresh air vent if I pop out the speedo and drive. That air will be HOT AIR in the summer and it must be leaking into the cabin somewhere.

ossiblue · 03-20-2010, 05:39 PM

I agree with Pete, I think the seals for the flappers inside the air box are shot. Very easy to replace once you disassemble the unit.

If the cowl opening is completely sealed and you're still getting fresh air through the defrost vents, try this: Move the middle lever on the dash control completely to the left so air is diverted to the floor. See if you still get air from the defrost vents. If so, there may be a gap where the hose connects to the defrost diffuser (up under the dash) or there is a gap in the seal of the diffuser itself. Also see if you get air through the floor vent.

80-911SC · 80-911SC's Garage

as said before most trunks allow air. that why most wont mount amp's etc in the trunk.

to reassure your self take 2" painter tape and run around the trunk gape .. try across the front first, you could need to adjust the catch , also take a good look at the seal, you can put a little grease on the seal at a few points, shut the lid completely then open and see if the grease has transfered to the lid thereby confirming a complete closure or a good seal. you can also use wire or other thin items and place under the seal to try to get the seal to "set" .......... try a bit and check back

later Steve

white99c2 · 03-21-2010, 12:25 PM

I added an adhesive backed weather strip that I picked up at Ace Hardware. I positioned it so it sits just at the back edge of the trunk seal towards the cabin.
BINGO - took out the speedo and no more air coming out of the hole while driving. In addition no more air leaking out of the A/C vents while the system is off and no more air leaking out of the defroster vents as well.

I hope this helps the AC system in the summer, we shall see. The less outside air that is leaking into the cabin, I would think can only help.

Thanks - Rob in Carefree AZ

white99c2 · 03-21-2010, 12:26 PM

mooney265 · mooney265's Garage

Rob, did this work in the Summer with your A/C? Thanks!!

Quote:

Originally Posted by white99c2

wwest · wwest's Garage

Quote:

Originally Posted by white99c2

I went to replace a dash light in the speedometer for the brights indicator and while I was driving last night I noticed it wasn't working so I popped out the speedo and played around with it. Got it to work just fine but as I was cruising along in my neighborhood I felt cold spring ait blowing out of the hole that the speedometer goes into.
Today I removed everything from the front trunk trying to determine where this air is coming from and I cannot locate the source.
Here is my concern, in AZ the summer 115 degree air is coming in as well. After the speedo is seated the air stops however I do feel a constant steady cool spring air flow coming from the defroster and A/C vent, it is not strong but I can feel it.
I blocked the air intake in front of windshield as well as checked the hood/trunk seal for leaks, I'm stuck, where else would air be getting into the trunk as I'm driving, the faster I go the faster it blows, like RAM AIR coming out of the speedo hole.

The opening in the front bumper for supply air for the front condensor blower is not what I would call well sealed.