BMW E46 Rear Arches - Rust & Corrosion

Here's a 73k E46 M3 we just discovered hidden corrosion (rust) building up inside the Rear Wheel Arches UNDER the factory seam sealer.
This video shows the basic findings and how all this starts from INSIDE the Wheel Arch.
So even if you have rust/corrosion on the outside of your Wheel Arch, it's highly likely it will be coming from the inside as this video and many of our others show.
Keep watching our channel for part 2 to be released soon showing the Redish Motorsport repair.
Thanks for watching.
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[@ppppugh7892]

I found that BMW's use of strategically placed cheap steel bumper brackets (rears), wing lower bracket (fronts) and the clogging behind the wheel liner caused most rust on the body. Just a silly cheap component bracket can cause the start of the rust which then causes a chain reaction to spread into the steel of the bodywork!

[@RedishMotorsportbmw]

That is true - we also see this as a common 'starting point'

[@ppppugh7892]

@Britewerks Two brackets on both rear quarters. One below the fuel filler and one on the rear bumper-side of the wheel arch (shown in this vid). The side without fuel filler, it's where the fuel filler would be in symmetry with the other side! One bracket on both front wings where the side cills/skirts meet the wing (fenders for US readers). Remove all the brackets, replace with new or clean them up, soak in Phosphoric acid to convert the rust, clean them up again, repeat the process with the acid. The Iron phosphate can remain as a top layer or you can remove it, prime the brackets, paint them, lacquer them. They should last another 8yrs ish! As for the bodywork following bracket restoration.... Redish knows best on that one, follow their lead. For the other issue of the wheel liner, you just need to know that a build up of dirt will lead to constant supply of moisture. Wet mud will stay wet for longer, dry mud will absorb moisture from the air in a humid environment. So basically, make sure the underside of the wheel arch is free of dirt. In the end, you're just fighting fire and rust will come whatever you do!

[@ppppugh7892]

@Britewerks I do actually. The fold in the wing arch panel, where the liner fits into is not even a useful channel for water run off. I say this because all it does is carry dirt into the cavity of the wing where the wing meets the side skirt. This will happen without fail! Plus, in this area there is one of those pesky brackets! It's those brackets which make the E46 an ever increasingly rare model because owners scrap them when the rust gets out of hand. They see every corner rusting and think its beyond repair, shame really. BMW's fault, cant think why they'd manufacture-in a defective item resulting in people wanting to upgrade after 10 years!! 😆 You could use the wax like a bond between the liner and the arch as you said. Good idea I reckon 😊 so long as you've cleared the rust totally beforehand! Good luck if you have a project to do.

[@andysvodafone]

Makes my scared to look under my E46!

[@LukesGamePage]

How much does the procedure coast broadly to resolve the rust issues on both arches? Thank you x

[@Decrepit_biker]

The rust on my E46 rear arches started from the frankly awful metal bumper clip! Terrible design!!

[@RedishMotorsportbmw]

That's right John - we're seeing the Clip as 1 of the issues too!

[@Vracktal]

I have an E46 330i facelift saloon with 93000 miles, and both rear inner wheelarches are worse than this video. Holes 2-5cm long all the way through the inner arch in multiple points and surface rust on the outer arch. Problem is it's not an M3 so probably not worth doing more than painting with hammerite and covering over the holes. :(

[@topproff2558]

Must have read my mind, I’ve been out in my drive tackling this all day. The exact same position. Such a shame these are such rust buckets. Makes all the other issues (vanos, bearings) seem mild in comparison. I’m at the point of considering scrapping the shell and selling the parts on eBay

[@RedishMotorsportbmw]

Sorry to hear that Mike. You're right - it's a big issue which can be quite costly if not tackled in time.

[@akerr911]

Yep same problem! Its also coming up from where the side skirt meets the arch. Haven’t addressed it as every body shop I speak with won’t guarantee the work and say it would come back in a year or two! My car is also an 04 and it’s on the job list so will be watching this closely.

[@gurjeetvirdi8813]

Ask Akerr got the same thing in the same place on mine. It’ll need cutting out and new metal putting in. I want to get mine done this year

[@topproff2558]

Exactly the same here on an 04. There actually a hole between the side skirt area and the arch now.

[@mohafzal2790]

Hello, is this problem inevitable on e46’s? It is a 14 year old car after all, Brilliant film btw

[@TheWretchedWorld]

Depends on which country you are in. I have an e46 323i in Australia with 340,000km on it and its been an outdoors car its whole life. No rear arch rust. Depends on climate if you are in a country that has a lot of snow and salt on the roads its pretty much guarrenteed.

[@mohafzal2790]

TheWretchedWorld ah, that makes sense, I live in Kuwait which has hot desert climate, pretty much all year round, and we never have snow, so I guess I’m okay

[@TheWretchedWorld]

@@mohafzal2790 yeah don't stress you won't get any rust

[@RedishMotorsportbmw]

As @thewretchedworld says, you shouldn't have any issues in a hot climate like Kuwait. It's mainly northern European and Northern USA / Canada issues where we live in a colder climate with plenty of rain and lots of opportunities for the local governments to throw salt down in the winter.

[@Tim82621]

I want to see how you guys treat that corrosion! Would be a good video! I’ve had it on many e36/46 in the past

[@RedishMotorsportbmw]

Thanks Tim. We already have 1 video on our KZbin showing how we replace the Metal Arches (and are about to release another one). Plus we're currently working on this car and have another 2 videos to release showing a newly updated method of how we address this common issue. Be sure to keep an eye on our channel for that video soon. Remember to hit the Notification Bell to be reminded of our new uploads. Thanks.

[@Tim82621]

Redish Motorsport awesome! I’ve got the subscriber bell on so i’ll get notified once you guys upload! Ill check the older one out too. Thanks for sharing your knowledge and satisfying us with the proper work!

[@TruckerMatty93]

How much would this be to replace and spray and all that?

[@joshuathomas5957]

@@RedishMotorsportbmw still waiting on the update...

[@Davewagon]

@@RedishMotorsportbmw Hi James, glad your uploading videos again. Seems a few of us are eagerly awaiting the second video of this repair (or the other videos you referenced about) hope they weren’t lost in lockdown ?! Take care, David

[@markST24]

Mine where so bad they crumbled on the inside but i treated them best I could with Kurust before fiberglassing over it and sealing with Waxoyl...

[@CB-bl4ts]

Oof my arches are also rusty but i didnt inspect them from the inside

[@GopNet]

it's funny how E46 can be mechanically reliable but have poor bodywork protection in return 😟I love mine and will love till it either dies, rusts away or crashes (hopefuly not) 😇 and it just turned 20 this year

[@jonhunter8737]

Classic poor design on the three series. Bad water tanks, bad hand brake assemblies, and comedy channels in the wettest part of the body work that appear to be engineered failure. Don't start me on litteraly everything else on the underside of my 320d also rotting away at huge expense to repair. Had a 316 E46 prior and this will be my last BMW.

[@j15mrk]

Jon Hunter I’ve owned loads of them and have one currently, thing is but a 330d drives brilliant it’s a shame the arches lets them down. Engine on it like a truck and pulls better than nearly all modern diesels.

[@ash20500]

I had rear arch bubble on my e46 330ci sport. Sold it before ever investigating. My 2003 e46 m3 has no rust on the car anywhere. It has been garaged in the winter for the past 7 years.

[@RedishMotorsportbmw]

Fantastic

[@EvanGoyuk]

I had rust on the quarters on my e46. I had my quarters cut off and had new ones welded in.

[@rabmc]

Evan Goyuk Evan if you don’t mind me asking what kind of £ is in that level of work.

[@EvanGoyuk]

Rab Mc I paid almost $3000 USD but I had very bad rust. My inner wheel are had to be cut and welded. I also had a brand new battery tray welded in.

[@rabmc]

Evan Goyuk Thanks for that, I’m in Scotland but getting to the point will need to do this, front wing is away and rear arches are slowly starting.

[@w75525]

Same here. And then within 2 years the rust came back.

[@rabmc]

Warren Hirst Even after it was cut out? Where rear 1/4’s? Surely I’d treated etc that can’t happen

[@thatsjustme1990]

Iv spotted to small bubbles on my drivers side rear arch, this video has made me scared to investigate further 😞

[@MartinThePanda]

My E46 has this problem. 😢 I'm gonna cut out the arch and replace it with a new piece.

[@faris9327]

On my 2 cars I have this shit, it's cancer following me from car to car, I can't believe that the top of the line my lexus LS 430 have rust in this spot this is ridiculous

[@rabmc]

I have it starting on my rear arches, not as bad as that (visibly anyway from exterior) just ever so slightly on mainly my drivers side, more so just off the arch way part on the horizontal part going towards petrol cap and its starting to annoy me, my front drivers wing needs replacing now due to rust bubbles also and started to break the paint. I thought my Sierra Cosworth was bad, in reality this is probably worse.

[@Himoutdoors]

this is why you must wash your wheel arches when you wash your car......

[@idokwatcher2062]

This is why sometimes I struggle for months with seemingly simple decisions to invest further in non-M E46 (e.g. LSD, Recaro seats...) it's just not worth it for a car that will rust out. For an M3 I could justify it as a car absolutely worth saving and tackle the rust every time.

[@Kortec_Racing]

Same on my e36

[@jasonking8812]

Same issue on my e39 530i sport although it's 2001 with 187k

[@nigelirving4703]

Mine has this too, a 2004 320D. I had then repaired 5 years ago, arches weren't cut out, rubbed down, filled and painted, lasted about 3 years then the bubbles started to come through again. 2 years ago I rubbed the outer lip down myself to do a DIY repair, purely cosmetic, I knew it would come back which it did a year later. Needs sorted again now, not sure what the approach will be as in cut out and weld new in our fill, I think cut out personally. When I clean the car I always clean the arches and lip. Once a year I give the underneath a pressure wash, any signs of rust get a liberal coating of aqua steel followed by dinitrol when dry. I'd be interested to see the repair and an approximate cost per arch. My old E30 had this but a lot worse, muck sat on top of fuel filler pipe which resulted in significant corrosion, that attracted a fiberglass repair.

[@callummunro5400]

Same with my car. Sometimes you can’t win. At least you are slowing it down. I’m trying a lanolin based product that I’ll put on every six months. I’m hoping repeated covering can seal it up.

[@danielrobinson2861]

Yeap...e46 bmw quality rust.

[@nelsonr32]

What sort of cost would rust like that be to sort? I’d expect £1000-£1600 one the paintwork has been blended?

[@e36fanatics]

For me it was 600 at small local shop but without any paint job... They completely removed rust and welded new panels on

[@subru3285]

My 1999 e46 has this problem fixed in BMW salon in 2010 now after 10 years I have to redone this work on the left side. On the inside side was looking good, but after checking I had to cut of 2 pieces and weld patches. I think that very important thing is to put wax every year in the holes which are cover by the plastic plugs to prevent rust. Unfortunately sheet metal over there is thin like paper.

[@RedishMotorsportbmw]

100% agree with this. Cavity waxing is seriously important. There wasn't much from factory when the car was new, then when repairers work in that area many don't install cavity wax at the end of the job and then it happens all over again.

[@andrewthompsonuk1]

On my old cars I go rust hunting once a year. Anywhere I see rust starting I pull out as much seam sealer as I can and smother the area with copper slip. The copper slip actually works, it soaks into the rust and stops it dead. However in this example as its a fantastic car they need to fix it properly. In my junk Hyundai Trajet one arch was worse than this I killed and removed the rust (cut out some metal) and filled it and made it look nice. Both sides were then smothered with copper slip once per year. 4 years later it has not rusted again. Yes its a hack but it works. Also great for brake pipes. Watching your videos you do it properly any less preparation and paint just traps moisture again.

[@soklot]

What is ''copper slip'' ?

[@andrewthompsonuk1]

@@soklot It's the copper colured anti sieze compound for bolts. My Mot inspector said it was good for brake lines. It saved all the brake lines on my 97 Z3 . That was 14 years ago and still good.

[@RedishMotorsportbmw]

Thanks Andrew, yeah regularly checking areas for corrosion is a great way to keep on top of potential issues.

[@soklot]

@@andrewthompsonuk1 Ah now i know what you mean. We call it copper paste.

[@ocultrecordofficial8930]

Mine are very rusty mate :))))

[@1rewd133]

2005 e46 with the same issue, passenger side worse than the drivers side. Planning to have them cut away and new metal installed in the near future. Would love to see this repair as one of your videos!

[@RedishMotorsportbmw]

Thanks for sharing. Yes, we've got 1 repair video of E46 Rear Arches already on our KZbin channel, are are making another one as we speak.

[@SandwichFresh]

good video ! This is the first visible part of the e46 which is getting rusty first i have it completely same on my e46 325 M sport with 57k miles [verified by bmw Lincoln] and im worried about replacing the whole panel on both sides but of course im gonna try to save them first ...thinking about filling the channel with rubberized undercoating or something to make it one whole part so the mud and water dont have where to sit do you know what i mean ? :D im interested in part 2 of this video go for it :D

[@SandwichFresh]

my car is 2003

[@andyallison9660]

Have exact the same problem with mine i also live in lincoln.. iam just glad the warmer weather is not to long away.. all e46s m3 or not are worth saving, mine is a 04 plate and I refuse to let these little bits of rust ruin my car completely. Its going to take a little bit of perseverance and probably a hell of a lot of swear words but I will get there

[@unixnerd23]

As someone who lives in the Highlands this is why I buy my cars from down south. You should see what salt does after a few winters.

[@richlee509]

Dont drive these cars in poor conditions. Get an old banger for winter

[@unixnerd23]

@@richlee509 These days I have an old RAV4 for the snow.

[@manishoker3484]

Re-shell it...

[@Astartesdave]

Yes have this on mine. Cut out the worst patched with a welder and some plate then slapped on rust converter, sprayed clear wax behind, por-15 etc to slow it down. It will come around again for attention at some point, when it does will be a full cut out and replace but looks a faff due to the shapes and my level of skill with metalwork. 53 plate btw

[@RedishMotorsportbmw]

Good work David

[@Astartesdave]

@@RedishMotorsportbmw your earlier video of this from three years ago where you bought replacement arches was something I dwelled on until I saw they were 700 ish to purchase 😔 fabrication options would be interesting as an alternative.

[@valcic1993]

I cut a corosion and weld new plate then put a kit and paint in spray but its bad color match

[@TheOpera4ever]

This car had to heavily expose to bad weather and salt I have an e46 m3 non of tha is an issue in my car! Is this car in the United Kingdom 🇬🇧????

[@TheMannystube]

What should be done to the lip? Should it be removed, left flat or filled? I have bough u-pol tiger seal would that work?

[@RedishMotorsportbmw]

We've been experimenting with this recently and are about to release another 2 videos on options on how we tackle this.

[@m1ercur1]

@@RedishMotorsportbmw any new vids on that?

[@jt4761]

Redish Motorsport look forward to the update

[@soundseeker63]

I doubt there are any E46s in the UK that have been daily driven and do NOT have some degree of rust on the arches. That car looked reasonably tidy from the outside but underneath it was a different story! At least my one looks like shit from the outside too so I paid a low price for it! I'd hate to spend £10k on a car like this thinking it was tidy then find out it was rotten as a pear underneath and needed ££££s more spending on it. Why does this happen? Is the galvanising on older BMWs really poor? Poor sealant? Too many dirt traps? Or all the above..?

[@e36fanatics]

This is why i no longer buy cars that are marketed as good condition because usually they arent... I rather pay much less for fixer up so atleast i can fix it and not be that much out of money

[@scottm6018]

Look forward to updates. Such a bad design on the e46

[@RedishMotorsportbmw]

Thanks Scott. Repair video coming soon.

[@scottm6018]

@@RedishMotorsportbmw nice one, will keep my eye out 👍

[@gaz7039]

Is this a new wing job? £000s?

[@RedishMotorsportbmw]

Hi Gary, no this wing (Outer 1/4 Panel) is likely fine and can be saved. It's just the Inner Wheel Arch Panel which always suffers first and needs replacing.

[@zee6100]

My E46 coupe is rusting in the same place but spreading out towards the rear three quarter panel 🙈

[@kamranhussain2343]

What do you guys charge for e46 rust repair?

[@gembi92]

My 320 have rust on the same place.

[@m3nine11]

Clean the arches regularly and this doesn't happen. Problem is if the previous owner didn't clean the arches then this is inevitable.

[@ash20500]

BavarianJunkie that’s the first thing I did on mine when I bought it. The arches were full of crud!

[@callummunro5400]

I had this took it to a body shop now it’s shiny. Really hope they did a good job! I wouldn’t know to be honest.

[@jt4761]

How did you end up treating this rust?

[@ianhand5006]

This is because the car hasn't been looked after properly during its life. It is essential to clean the car underneath as well as on top. This is still an old car though, and I bet the arches were still good at the end of its design life of 12 years. Great video, by the way!

[@Decrepit_biker]

Its actually the metal clip for the bumper that often causes this issue, it breaks the paint as the bumper flexes slightly and then its all down hill.

[@RedishMotorsportbmw]

That's right Ian - it's an area that needs checked/cleaning regularly to stop the build-up of damp mud/dirt which causes this issue to fester.