I have had tremendous luck using the expert advice on this forum in dealing with the various issues on my 1990 928 S4 so am trying again for the latest one. I notice after driving in rain (yes I know why would I drive in the rain,well
this is my great fun to drive Dailey driver) that the inside of my glove box is damp as well as drops of water on my passenger side floor mat. At least at this time I do not notice amounts of moisture on the fuse panel under the wood cover under the floor mat. Ok obviously a leak in the firewall/vents some place so if anyone has any suggestions or places I can get info on getting this issue fixed it would be greatly appreciated.

 

Have you cleaned the sunroof drains?

 

Based on your report the water is probably coming from the windshield seal.
NOTE the blower box seal is also a suspect,
but since the water is in the glovebox it suggests a source higher than the glovebox.
And the fact you report that the CE panel appears dry,
The blower box seal failure will leak onto the CE panel.
NOTE the BB seal can still be bad, use a good flashlight to inspect

 

Thanks. I will check out the BB seal and reinspect the sunroof drains

 

Don’t forget to clean out the drain in the fire wall passenger side. That gets clogged and water gets into the cabin in that area too. It is a black flap on the firewall in the engine bay. Remove the air box to get to it.

 

If you have a smoke machine, you can put it inside the car, close it up and from outside the car see where the smoke is escaping. That's where water is getting in.

 

I think a better way would be to get a hose and spray it in different areas outside the car ,
while someone with a flashlight is looking at the area that’s suspect
Note remove the floor carpets in the front and both parcel trays and also the glove box assembly,
with a helper on the hose spray from low to hi
Note make sure you have a properly fitted cowl cover under the hood .
And as Ed pointed out the firewall well in front of the BB inlet is clear of debris a bore scope will easily tell the story here

Note on a dark car in a hot environment that’s sees a lot of sun exposure,
the seals will dry out faster that goes for the windshield seal the BB seal and the door seals and the sunroof seal,
also the rear drip panel on the back of the sunroof panel will warp and crack

 

When I had that problem I found that the drain hose was partially pinched behind the washer tank in the RF fender well. It was also plugged.. Cleared it with a lenght of weed whacker line carefully as not to push the hose off the connection at the sunroof drain. Now I can hear the suction created as the channel drains when I test it. (If it is really plugged you can heat, flatten the line a little and twist it like a drill bit and put the line in a drill.)

 

Thanks folks. This is exactly why this site is so valuable to owners of these fine automobiles. This really helps in reducing the frustration factor when working on these 30+ year old cars