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Subject: Repair for water leak around A/C copper pipe in firewall Author: DavidC (moderator) : member since December, 2003 : 12116 posts Posted on: 2004-05-15 00:31:22

After repairing a severe leak around the heater box and installing all new carpet and padding, I noticed yesterday (during a rainstorm) that we had a bit of water in the passenger footwell near the firewall. It appeared to be dripping from above behind the glovebox.

I figured it was just condensation from the A/C pipes since we had a hard time getting the black foam insulation block around the pipes when everything was reassembled. However, after removing the glovebox and using a garden hose to spray down the front of the car, my wife noticed that the leak was emanating from the copper pipe that goes through the firewall to the engine compartment.

It appeared that the rubber grommet was not providing a good seal, so we purchased a tube of McKanica Red High Temperature Silicon Sealant from AutoZone. It comes in a pressurized can with a nozzle, making it easy to get a bead in hard to reach places like the underside of the dash where the copper pipe enters the cabin. This appears to have solved the water leak.


The high temperature silicon sealant, approximately $9 at AutoZone.


A view of where the copper pipe enters the firewall from the engine compartment. The red area around the pipe is the high-temperature silicon sealant.


A view of where the pipe enters the cabin, behind the glovebox, with the high-temperature silicon sealant generously applied to the inside and outside edges of the rubber grommet.

David Cecil
'97 740iL, 120k miles
'86 735i, 94k miles
'77 320i, 140k miles

www.e38.org has links for everything about your BMW 7-series automobile

• Repair for water leak around A/C copper pipe in firewall (pic) - DavidC 2004-05-15 00:31:22 (5357 views)
  • David have you checked the drains in the cowl area? - kff 2004-05-15 00:42:34 (689 views)
    • Yes, fixed those last fall and they were completely clogged, too (nt) - DavidC 2004-05-15 00:55:33 (557 views)