BMW Forums : BimmerForums banner

1 - 14 of 14 Posts

·
Registered
Joined
·
14 Posts
Hi, forum newbie here :) I'm wondering if anyone has any advice on a long-term solution to my rusty rear arches? The rest of the car is in excellent condition, it's a 1997 328i Convertible which I've owned for about 6yrs. A couple of years ago I noticed some small bubbles of rust coming through on the rear arches. It turns out that the design of the rear arch lip collects a phenomenal amount of wet mud off the country roads I use. I had the rust proffessionally treated (lead loaded) twice in the last 2yrs and it's just beginning go come through again! :( Is there an aftermarket wheel liner (as per front end) I can buy anywhere to stop mud building up inside the wheel arches? They seem to fill up with mud within the space of a week, and it's not as if I'm off-roading! Would I be better off buying entire new rear wings and having them galvanised or something? Is that even feasable?

Any help appreciated!
 

·
Registered
Joined
·
8,981 Posts
There are arch repair kits available, although they were planned for the saloon I think

http://www.bimmerforums.co.uk/forum/f17/1997-e36-318i-wheres-best-cheapest-for-arch-t46694/

Once done, I would paint the inside with a good few coats of bituminous paint -
http://www.toolstation.com/shop/p88792

And then maybe some stonechip after. Bituminous paint is thin tar, which always stays a little tacky, and it's cheap too, so it'll flex and can ever reseal itself. The stonechip paint is similar but with more wax added, so it acts as a shock absorbing coating for the road debris.
 

·
Registered
Joined
·
14 Posts
Discussion Starter #3
Thanks! :) I'll see if I can find out if they fit the convertible. I'm surprised the rust is coming through again as I did give the insides of the arches a good few coats of Waxoil last time they were repaired.
 

·
Registered
Joined
·
250 Posts
i probably the most annoying thing about the e36. i have mine treated and resprayed last year and the rust is coming back again. its a real pain in the back side especially when you pay about £300 for the panels to be sprayed. sometimes i think of just leaving it....
 

·
Registered
Joined
·
14 Posts
Discussion Starter #6
I agree, its a right pain and detracts from an otherwise great car! I was really hoping to find some sort of aftermarket plastic wheel arch liners for the rears to keep the mud and salt from accumulating in the lip of the arches.....I'm really surprised theres nothing like that on the market as I've seen plenty of E36's that are bubbling away.
 

·
Registered
Joined
·
1,824 Posts
As said, the only way to fix if the metal is rotten is to cut it out.
Any new pieces welded in should have some sort of high zinc content primer on the reverse side and the welds should be 'continuous', as in there shouldn't be any gaps once all the welding is done. I've seen repair sections welded in where there is a weld ever cm or so, perfectly strong but still a gap for moisture to form.
Once it's all done some kind of cavity wax should be sprayed in, not waxoyl as it's too thick, you need something that will seep into every seam.

If you're looking to prevent your otherwise good arches going then the only way it to keep them clean really, remove arch liners etc and clean it all out periodically. Plus spraying some wax inside the panels (remove boot trim to access) in the summer months will help.
 

·
Registered
Joined
·
995 Posts
The E36/E46 rear arch design is a superb mud trap - it's actually U shaped in profile. Apart from keeping the arches perfectly clean in winter (which almost nobody ever does), you should also take the rear wheels off every few months and inspect the inner arch lip. I just caught some rust on my '95 yesterday on the inner return flange, sanded it down, Kurust rust treament and then some top coat before greasing both arches. It's the only way.
My '93 Coupe is not so lucky. I managed to catch one arch before it went nuclear, but the other side is not so lucky - it's having a new outer arch welded in next week.
 

·
Registered
Joined
·
2 Posts
Go to carz2.co.uk. They do almost any repair/replacement panel, at very cheap prices. They do wheelarch repair panels for saloon and coupe £31 each. I hope this helps.
 

·
Registered
Joined
·
528 Posts
It is a shocking dirt trap. When I got mine the paint was just bubbling, but wire brushed it back to the metal which was still solid luckally, then cleaned and wire brushed the whole arch with the rear wheels off and under sealed everything! then went on and re-undersealed the whole underside.
 

·
Registered
Joined
·
2,990 Posts
2 door arches

RH

LH
 

·
Registered
Joined
·
2,990 Posts
It is a shocking dirt trap. When I got mine the paint was just bubbling, but wire brushed it back to the metal which was still solid luckally, then cleaned and wire brushed the whole arch with the rear wheels off and under sealed everything! then went on and re-undersealed the whole underside.
Unfortunately the rust that causes issues is most often from the inside out from between the inner arch and quarter panel not in the welded seam. No amount of cleaning and sealing from outside the car or under the arches will help when this is the case.

Note:
With arch sections people tend to use the whole panel. In fact you should use as little panel as possible that takes oyu back to solid steel. That way in a 5 or 10 years if gone again you can cur out a little bigger. Also if only the edge has gone it is perfectly possible to repair into the flare and not touch the large flat are thus saving a lot of distortion risk and filling onto a larger area.

A skilful but weld on thin steel is unlikely to be completly water tight using the common mig and often pulsing technique.

However, it does have a big advantage over the easier lap joint as it doesn't have two layers in close proximity to suck in water like between two layers of glass which are very hard to seal on the inside perfectly, as even if painted imperfectly with seam sealer because there is no channel it cannot draw water along.

However a butt joint is much harder to cut and file to shape, avoid burning through and needs a steadier hand.

A lap joint using a joggler or edge setter will give a very strong flush lap joint with only moderate skill. Lead loading this will hold back any rust that develops for a good few years but is a skilled three handed job.

All the above of much preferrable to a really cheap job where the whole repair panel is spot welded on top over the original adding nothing to strenght, creating a huge rust trap over a much larger area and weighting down the quarters in loads of filler.


No warranty of any kind implied or given, just my ramblings.
 

·
Registered
Joined
·
995 Posts
I've just had a wheelarch replaced on my Coupe - it cost £300 to cut the outer arch off, clean up the inner one, weld a new outer arch on and finish/paint. They alsoput lots of sealer in so mud cannot get lodged in there.
 

·
Registered
Joined
·
2,990 Posts
I've just had a wheelarch replaced on my Coupe - it cost £300 to cut the outer arch off, clean up the inner one, weld a new outer arch on and finish/paint. They alsoput lots of sealer in so mud cannot get lodged in there.

Make sure its sealed / waxoyled / painted from inside the quarter too, that's almost as important to it lasting.
 
1 - 14 of 14 Posts
Top