My bulkhead was bad, the biggest culprit in my case was the insulating foam that Austin deemed fit to introduce most definitely wont be going back in. Used Bilt Hambers Deox Gel on mine, removed 100% of the rust.
Exactly what caused mine... I think its only surface rust ATM as there is no sign of rust on the inside of the car... but yea.... Will definitely get sine deox gel and get the rust out .
Just done a similar job. Good advice above. It's not too tricky once you've removed as much stuff as you can including the MC. Deox gel is really good.
regarding the master cylinder... first off, what is it for, and is it just bolted down to the bulkhead crossmember or is there a pipe leaving the MC into the body? Im asking this as I would only unbolt the MC, lift, sand underneath as well as possible and then coat. I dont want to remove it if it would cause me to refill the fluids (never done that before) or have me do more then needed. Otherwise Id just tape it off, sand around, and move on
I would go a little bit more heavy than a wire brush in a drill. Now this is speaking from experience. Use a grinder with a twisted wire cup. You can get various types and they make a better job of removal than a drill and wire brush.
Still do as Alex said though and cover the engine. Remove components as much as possible to free up as much space as possible.
You can always use a Dremmel as well. Then use something like Bilt Hamber Deox gel to treat afterwards. Use an epoxy primer prior to paint.
Will try my best. My brother has a really small bosch hand held grinder and ill see if i can get some white brush attachments for it. Otherwise ill dremel/flap disc grind it out.
Wouldnt it make sense to get a paint striper, apply and remove the paint, then hit it directly with deox gel as its mainly just surface rust? Just thinking of alternatives....
No is the answer to the paint stripper. Basically this is fine for its purpose of removing paint but then just to cover the area in a converter will be a waste of time.
If you are not aware the basic bodywork of a mini is thin, 0.9mm and that part of the bulkhead above the crossmember is that thin. Now again speaking from experience here (have a look at Project Paddy in my signature) once its pitted it needs cutting out, but as a stopgap do what we have previously mentioned, a twisted wire cup in a small grinder will remove all of the surface rust which you will need to do no matter what with any converter.
If you do not do this it will rot out quickly. The crossmember is a lot thicker, a minimum of 1.2mm so can take a lot more abuse with regards to rust, however the same applies. You must remove all of the surface rust as far as possible.
Now your timescale of 7-10 years before a respray / resto is optimistic. My clubby looked ok and could have gone on for a couple of more years but there was rust lurking and the longer you leave it the worse it will get.