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BMW E30 Damp Carpet – Water leak – 325e, 325i and Other BMW Models

October 20, 2010

Q
I have a BMW 325es 2 door. I noticed that the floor area (carpet) is damp on the driver’s side front. Most of the dampness is towards the center area and the console area. At first I thought it was condensation from the A/C, but I noticed it again yesterday. What are the possible causes and how do I correct the problem?

A
First, let’s make sure the wetness is not from engine coolant. Have you noticed any odd smells when the heat is on, sort of like maple syrup? Is the wetness slippery? Either of these conditions would point toward engine coolant and a leak in either the heater core or the control valve. If the wetness is not from engine coolant, we have a few possibilities:

* Water entering from under the floor. Make sure that you do not have a rust through area in the floor.

* Water entering through the heater/AC box. The air intake for the climate control system is in the cowl, forward of the windshield. Obviously, both air and water will enter through the plastic grills at the base of the windshield. However, on most BMW models, the water should drain out through a drain hole and discharge tube, on the firewall.  On your E30 chassis, there is a drain at the base of the air/wiper/blower motor cavity, on the passenger side, that goes through the firewall and has a rubber 90-degree nipple on it at the firewall (see the attached photos for E30 3-series 84-91, 318i, 318is, 318ic, 325e, 325es, 325i, 325is, 325ic, 325ix, M3).

The drain hole/nipple may be clogged with debris which could allow water to build up in the cavity and overflow into the heater/AC box. Additionally, you may have a rust hole or leaking seam in the air intake cavity which would allow water to enter the interior. We have seen more than one E30 (3 series 84 through 91) develop a leak at the forward bottom, driver’s side, of the air cavity … allowing water to leak behind the firewall insulating and rust a hole through the firewall in the area just above where the brake booster mounts. You’ll have to do some detective work to try to trace backwards to the origin of the wetness. Feel free to let us know what you find.

Click HERE for E30 HVAC iar intake box drain tube

2 Comments
  1. robert permalink

    i have same problem only on passenger side. 1989 325i conv. looking for attached photo of firewall?????

    • We’re sorry for the missing photo. The photos are now in place.

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