I just picked up an E30 M3 last Thursday. After I got home, I started to clean it and noticed the carpet was damp when I pulled it back a bit. I took it out and found several spots of rust on the floor pans; front driver and front passenger side. I'm pretty sure the PO didn't know about it; you couldn't have seen it with the seats and carpet in. The rest of the car is clean.

Anyway, does anyone know of a place that sells replacement pans, or am I just going to have to use sheet metal to patch it? Also, the regular E30 floor is the same as this, correct? The parts I would need to cannibalize are right where the rubber pad on the carpet ahead of the pedals is, where the accelerator pivots, and right in the middle of the passenger footwell.

Whoa, wait a minute, is this surface rust or rusted all the way through, ie a hole? If it's just on the surface, get some metal prep at a body and paint supply, put on some gloves and eye protection, and use this with Scotch-brite pads to scrub the rust away down to bare metal. Then prime with an anti-rust primer, and if you want to be factory correct paint it with body-color paint like it was originally. This is under the carpet so honestly I would use a brush, but a spray can can be OK, although you need to cover up interior parts to protect from overspray. Honestly I would recommend the brush.

If this is a hole all the way through, it's not a DIY job for a beginner.

Now the real question is to figure out where the water is leaking in....maybe plugged A/C drain, maybe leaking windshield gasket, etc. etc. Look on S14.net under the Rust/Water FAQ

The question is not if the PO knew, it's why didn't you check before you bought? Not to be harsh but damn I see a lot of these posts "I just bought this car and x is broke". A professional appraisal of a car BEFORE you buy it is money well spent if you are not SURE you know what you are looking at.

That said the car looks good in the photo, I would be astounded if you have rust through the floor pan!

The holes are all the way through. I know what I'm going to need to do, just wondering if anyone sells replacement pans, as they do for older Porsches and others. The whole pans probably don't need to be replaced, but I think it might be easier to do that rather than cut and patch three different holes.

I haven't been able to figure out for certain where the leak is coming from, but I suspect it's the windshield gasket; it doesn't look like it's seated properly, and it was recently replaced.

I did check for rust when I looked it over, as did my dad. Between the two of us we've bought 10 older cars in the last 6 years and never had a problem; we pretty much have the PPI down. Everywhere else on the car is great, even under the windshield (I have pictures from when it was replaced). I swear it looked solid underneath...it was COVERED in dirt though, so the little bubbling that is visible underneath was probably hidden. The only reason I found it was because I pulled up my carpet, otherwise it would have been there for a long while without me knowing.

Wow. Lookikng at the photo, I would not be checking for floor pan perforating rust either. Sounds like your Dad and you are more experienced at the old car game than most.

If possible post some photos of the holes, perhaps someone like Paintpro will have some good ideas if you show where it is and how large.

Consider the "no weld" repair kit offered by Eastwood. Could save you some hassle. For the most structural repair, MIG or TIG welding would be king, but if the holes are not too big a simple patch may be enough. Since it's under the carpet you don't have to work as carefully as on something that shows.

To get to your most important question, I don't know if new floor pans are available or if they are the same as other E30 cars. Sheet metal is probably available but spendy, getting the parts you need from a junkyard or just fabricating from new sheet metal may be more practical.

The M3 windshild is unique to the car IIRC, and there are more ways to install it wrong than right apparently! Don't neglect the A/C water drain, they plug and put water in the floorpan pretty frequently.

Good luck!

There is a tube in the engine compartment on the firewall. It looks like a elephant trunk. it may be clogged and may be the reason why water is going inside. Just pull it off and clean it out.