Forum:
Ok, only got a fourtrak (2.8td, SWB, 1990) very recently, and it's got some fairly serious corrosion in the rear wheel arches (fairly big holes.......). Apparently this is a fairly common problem.......
Had a crawl about underneath and the chassis seems to be sound, so not too worried about that.
My question is can you get pre shaped replacement arches to weld in, or do you have to start with sheet metal, shape it yourself and then weld in?
There is a good amount of sound metal to weld to, but will probably rivet and weld, just to be sure 
I intend to treat any other rust spots I find and then underspray - again, just to be on the safe side
Oh, one other thing - is it best to weld the replacements inside or out?
My initial thoughts are replacement panels in arches themselves, then infill on inside before refitting carpets and seat......... but if there's a better way to do this, I'd appreciate knowing
Ok, also, at the moment it has static adjustable seatbelts in the back (although centre lap belt is missing, not a problem to me, easy enough to replace), is it easy to replace with retractable ones, and if so are there any specific ones that work best?
Think that's everything I need to know for now
Thanks
Underneath The Arches
No replacement wheel arches are available, surprising considering the numbers of Fourtrak's on the road with the same problem.
Begin by marking out the profile very carefully, make up the outer arches from sheet metal, cut the old ones away to good metal, look underneath the wheel arch, and cut away and make good underneath with 2mm plate.
Fit the outer sections and spot weld with MIG or TIG, finish with filler to ensure a smooth finish. Remove the inner rear trim panel to gain access to the inside of the wheel arch, treat this with thinned Waxoyl to allow it to penetrate between the joints. Under the wheel arch, spray on a couple of coats of Schutz, this is grey and very elastic, and resistant to impact damage, paint on this a couple of good coats of industrial paint, and when it is dry, apply several coats of brush on underseal.
Wheelarches cannot be obtained from Daihatsu, but complete quarter panels can, alternatively you can get Toyota wheel arches which require cutting and modifications, but look ok if done properly.
REAR ARCHES
Same problem exists on the Sportrak and in particular where the rear seat belts mount. Only real solution is to plate. Like wise self fabrication is the only solution.
As for the outer part of the arch, a lot ot the problem seems to start with the plastic extended arches which are bolted using self tapping steel screws into those dreadfull spring clips. The rust starts quite rapidly and then spreads beneath these over arch extenders and once detected has often gone too far. I would advise all owners to fisrtly remove the attachments, check and repair any signs of rust and then replace the arches (plastic) using stainless nuts, bolts and washer, the nut and washer being on the inside of the arch lip. I have a 1991 with no plastic arches and no rust on the arches except a small amount aroung the seat belt mount but the 1996 Anjou with these plastic extensions had rust around every attachment. I scurfed all off and treated and then waxoyed the metal and paint beneath the plastic arch before replacing it with the said stainless steel bolts. Hopefully that will prevent the culprit from getting hold again.
Worth doing the fronts as well!!
OLDMINIMAN
M J Young
Electrolytic Reaction
Do not use stainless steel fasteners on mild steel, as the vehicle uses its body for the earth, the current passing through causes a situation known as electrolytic reaction. This phenomenen means accelerated corrosion of the less noble metal, i.e. the mild steel, this corrodes instead of the stainless steel, and makes the situation worse.
Use plastic contraceptive type fasteners (plastic with a screw up the middle) or the original type screws, coat these well, and periodically spray with old engine oil.
USE OF STAINLESS STEEL
Hi Assasin,
Thanks for the advice on the stainless although I have been restoring Minis for a number of years and haven't come across this problem. A number of vehicle restorers use stainless nuts and bolts with great success and they are supplied by specific restoration firms with the only warning that they should not be used on structural load bearing items, eg Engine Mounts, as their strength is reduced by the process. I am now in a slight quandry over whether to continue using these. The original Mild steel seems to have such a short life even if protected with grease or underseal and certainly those hardened self tapping clips cause more problems still as they rust immediatly as well as scratching the panel went first clipped on.
I have heard of this problem and have had the problem when using alloy panels (Land Rovers) which react to most things but I never realised the problem existed with the stainless nuts and bolts.
You live and learn Mate.
OLDMINIMAN
M J Young
Thanks for the info guys,
Thanks for the info guys, much appreciated
This one does not have the plastic extension things on the arches, just a fair amount of rust on rear wheel arches.
Have decided that I can't be bothered to do the welding myself so have booked it in with a local guy who has a great reputation with 4x4s
For information, there is no rust around seatbelt mounts at all - I want to fit retractable seatbelts in the back, instead of the static ones currently in there - I apologise if my wording was not clear previously. Have had a mooch about and I think that pretty much any kind of retractable seatbelt will be ok, as long as the mounting is not too bulky - will be searching scrap yards soon!
Grateful for any further info too - would rather know stuff than not
Cheers