I have a 1994 318is. I've had a recurring electrical problem for quite a while. My car's broke down twice lately with a waterlogged ECU. Water comes in thru the bulkhead, and the only way I can cure this is a new ECU, according to my garage.

So I'm looking on the net for common ECU faults etc, and find:-

BMW 3 Series (1990-98). Both Bosch Motronic and Siemens engine management ECUs suffer water damage due to blocked heater fresh air inlet drain hose. This hose is triangular in shape and is intended to drain any water which collects in fresh air inlet. Leaves and other debris block this hose which allows water to build up eventually flooding ECU compartment and causing ECU failure. The fix is easy - shorten hose by 2cm at bottom with snips + clear drain pipe with thin wire as part of winter service.

I'm intrigued by this as I also have a problem with my heater not working to full effect. So maybe I can cure 2 problems in one easy operation...

But no. Can I see a hose "triangular in shape" ? Can I ****.

Anyone know where the "fresh air inlet drain hose" is?

Is this thing total BS or what?

Cheers.

I'm afraid this may not be what you think this is. I believe this is the samll hose that drains water that collects in the cowl in front of the firewall. That's the area where the fresh air intake is. the hose lets water that collects there drain out and directs the flow down the engine side of the firewall. That's why it's called the fresh air intake drain hose. If it gets obstucted, the water will collect and overflow into the area where the ECU sits. Not a good design.

Look for the drain hose on both sides. I think it is #5 on the diagram below.

179028

I appreciate your response, thanks.

However, that diagram is impossible to read.

And I really can't see a hose anywhere near the ECU. Maybe there isn't one on my car.

Can you describe in more detail where this hose is or what it is connected to?

Let's try again. Hopefully, this picture is more clear.

Anyway, the hose attaches to the firewall. I think it's a little below the cowl. Unfortunately, I don't have an e36 here to take a picture for you.

The hose is not near the ECU. It is in the engine compartment on the firewall. I think the problem is that the water collects in the cowl below the windshield and overflows into ECU compartment.


179083

Again, very much appreciated.

I'll let you know how I get on.

They say this is quite a common problem. Anyone else out there had it? How did YOU solve the problem? (new ECU, sold the car?).

I was looking around the area near the ECU originally, but the pipe is actually on the other side, behind the engine block.

Sure enough, there was a bit of cardboard, a bit of chip board, and 13 years worth of dead leaves, dirt and sludge in there.

Yet to find out if this will improve the performance of my heaters, but the main thing is I'm pretty sure the waterlogged ECU problem will not re-occur.

THANKS VERY MUCH FOR YOUR HELP STEVE!

Now I'm gonna give some serious verbal to the so-called BMW specialists who I've taken this problem to twice. They obviously don't know about this pipe, or browse the internet enough!