[rjfaulco]

Hey all, wondering if anyone knew where the AC drain line for the car would be. Tried googling and looking and past posts but with no luck. Basically just bought my car used (2020 m40i) and immediately started having problems with a soaked floorboard. Particularly directly under the seat. I tested the roof drain by throwing water on the car and can see where it drains fine. However ive never seen water come out of the car after parking, so I’m left to assume that my AC could be clogged and backing up under my driver side seat. Any advice?

[StanDiego]

Originally Posted by rjfaulco

Hey all, wondering if anyone knew where the AC drain line for the car would be. Tried googling and looking and past posts but with no luck. Basically just bought my car used (2020 m40i) and immediately started having problems with a soaked floorboard. Particularly directly under the seat. I tested the roof drain by throwing water on the car and can see where it drains fine. However ive never seen water come out of the car after parking, so I’m left to assume that my AC could be clogged and backing up under my driver side seat. Any advice?

I can't help you with the drain line but did you turn off the AC to confirm that's where the moisture is coming from? If the AC is off, there'll be no condensation thus no water to drain.

[tracer bullet]

For my 135i I sometimes use the Realoem site, that has diagrams and part numbers of everything. Find your car, navigate through the myriad advertisements, and eventually dive into the section that might contain what you are looking for. It would show you the shapes of parts, how they attach, and so on. If you look there for the A/C setup, HVAC system perhaps, whatever - it may show the drain line itself as an item that can be bought. Then you might get an idea of where it attaches, what shape it is, and where it might eventually drain out. With that info there's a chance you could figure out how to clear it?

[Wynnsiensheng]

I think there was a recent thread that talked of this problem. From memory the OP had a windscreen replaced and thought it might be that, but it turned out to be a blocked drain.

I can’t remember the details of how it was unclogged although there was quite a bit of detail.

Maybe if you search and include replacement windscreen leaking, it might find the thread

[Kevin45E]

Originally Posted by Wynnsiensheng

I think there was a recent thread that talked of this problem. From memory the OP had a windscreen replaced and thought it might be that, but it turned out to be a blocked drain.

I can’t remember the details of how it was unclogged although there was quite a bit of detail.

Maybe if you search and include replacement windscreen leaking, it might find the thread

I think this is the post being referenced.
https://g29.bimmerpost.com/forums/sh....php?t=2007884

[rjfaulco]

Originally Posted by Wynnsiensheng

I think there was a recent thread that talked of this problem. From memory the OP had a windscreen replaced and thought it might be that, but it turned out to be a blocked drain.

I can’t remember the details of how it was unclogged although there was quite a bit of detail.

Maybe if you search and include replacement windscreen leaking, it might find the thread

I found this one and assumed his issue may have been the roof drain line, don’t think he ever confirmed which drain line was clogged. I threw some water on my hood and saw my drain line work ok. But I’m definitely not seeing water come off the car after driving like I’d expect from the AC. I just don’t even know where to begin when looking for the ac drain

[StanDiego]

Originally Posted by rjfaulco

Hey all, wondering if anyone knew where the AC drain line for the car would be. Tried googling and looking and past posts but with no luck. Basically just bought my car used (2020 m40i) and immediately started having problems with a soaked floorboard. Particularly directly under the seat. I tested the roof drain by throwing water on the car and can see where it drains fine. However ive never seen water come out of the car after parking, so I’m left to assume that my AC could be clogged and backing up under my driver side seat. Any advice?

The diagrams in the attachments should be able to help you isolate the location. The second diagram of the cabin air filter is just to give you a reference point.

https://www.realoem.com/bmw/enUS/sho...diagId=64_2406

https://www.realoem.com/bmw/enUS/sho...diagId=64_2392

[GerryC]

Originally Posted by StanDiego

The diagrams in the attachments should be able to help you isolate the location. The second diagram of the cabin air filter is just to give you a reference point.

Housing Parts

Microfilter

The Housing parts diagram is the one showing both of the drain lines. There are two. One from the bottom of the microfilter (the long tube in Item #1) which flows over and feeds into the main drain line (Item #4 - the 4 and 5 labels are reversed in the diagram.)

The microfilter and the start of its drain is in the front of the passenger footwell. That drain runs between the AC housing and the firewall towards the driver's side.

The drain (shown below, upside down) snaps into the bottom of the housing near the driver's side footwell. The drain exits through the floor pan near the front left side of the transmission.

[rjfaulco]

Originally Posted by GerryC

The Housing parts diagram is the one showing both of the drain lines. There are two. One from the bottom of the microfilter (the long tube in Item #1) which flows over and feeds into the main drain line (Item #4 - the 4 and 5 labels are reversed in the diagram.)

The microfilter and the start of its drain is in the front of the passenger footwell. That drain runs between the AC housing and the firewall towards the driver's side.

The drain (shown below, upside down) snaps into the bottom of the housing near the driver's side footwell. The drain exits through the floor pan near the front left side of the transmission.

Awesome info - I’m almost certain that’s what has to be causing my problem. I took the car to a local shop who gave it a shot at a fix but I’m not certain it worked. Still no water draining after driving - can’t tell if there is new water since I still feel dampness underneath the seat.

Is this drain line accessible inside the car by taking off panels near the footwell? Almost looks like this drain piece is by the pedals

[GerryC]

Originally Posted by rjfaulco

Awesome info - I’m almost certain that’s what has to be causing my problem. I took the car to a local shop who gave it a shot at a fix but I’m not certain it worked. Still no water draining after driving - can’t tell if there is new water since I still feel dampness underneath the seat.

Is this drain line accessible inside the car by taking off panels near the footwell? Almost looks like this drain piece is by the pedals

Not sure how to get to it. I expect you would have to remove the center console. In any case, it's not a simple task.