Newby so sorry if this has been dealt with.
Lucky enough to have found a low mileage 2000 Mk 2 that has always been garaged, chassis rails are fine but I want them to stay that way. Is it simply a case of spraying Waxoyl into every hole once a month? and keeping it garaged should help? is it just a matter of time before they do go? grateful for any tips
No one can give you a definitive answer on that one as in reality you would have to remove one and do microscopic examination of sections an old good condition chassis rail.
The best you can do is cover the inside and outside in some form of underseal and hope for the best but there may be some dampness already in there.
So get them covereding them with underseal.
I really wouldn’t use underseal in the box section as it will just seal any moisture and rust in place, a better idea would be to use Waxoyl, Dinatrol or similar as it will penetrate any gaps between panels. Even oil squirted into the chassis rail would be better. I would wait until summer before doing it as it will be warmer and drier.
When I was at tech several years ago one of the instructors told us of a brand new BMC Mini that was given a PDI in the workshop. The owner was asked if he wanted the underside coated in underseal, he replied that he “didn’t want any of that muck” on his car, he wanted the underside covered in old engine oil. 30 years later the car still had its original rear subframe which wouldn’t usually have lasted more than 10 years if you were lucky!!
“underside covered in old engine oil”
Sounds like our old Vectra, still no hints of rust at 18, but it took fifteen years to find the tiny damaged O-ring (crankshaft sensor) that was losing the oil, up to half a litre per year. I needed to clean the worst of it off underside and back of the engine each year to get through the MOT.
thanks for the replies, are there any pics out there to show the best access holes to inject the protection? also, if I remove the front bumper, are the rails open at the facing end so I can gain direct access to the internal cavity?
cheers
It’s worth taking the front end of to have alook and tackle 
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I hope the pix come out.
Twice failed to upload photoshop pix !!
http://s998.photobucket.com/user/marparphotos/media/P1190896_zps50a407e8.jpg.html
http://s998.photobucket.com/user/marparphotos/media/P1190898_zpsdc124123.jpg.html
Third and final attempt.
that is VERY useful, thank you, come the warmer weather, I will get to work, is it a massive job gaining access, sorry for all the questions, I can strip down a Mini no problem but new to these
Believe it or not, once you have done it once you can have the nose off in 20 mins. Removing the under engine tray results in nearly all of the self tappers shearing off usually. I drilled to adjacent metal and used self tappers to refix it.
Bannedbiker
I was assuming the poster would recognise the products you mentioned in your post as underseal. Which particular products are you recommending the poster does not use considering the product has to be sprayed into the chassis rails.
It is a pain of a job as getting the plastic trays off usually mean getting rusted bolts and screws out which always make a 20 minute job last ages.
It is a lot better to have the car on a lift to do the job but it can be done on axle stands just more of a pain.
There are holes under the rails to get in there as well as the front opening.
I’m not sure about getting into the internal area behind the suspension springs.
If you can get a local garage to do it and you trust them, that is a better idea to doing it yourself on the ground but it’s up to you.
I think I will spray some aersol stuff through the holes as a temp solution and then come warmer weather, take the front off, clean out, paint inside of cavity with hammerite and then plaster with grease,
thanks for the heads up re the self tappers, I wont panic when mine do the same,
now I have had a few drives, I can see why they are liked so much, in time the mark 2 could become a classic, I will do everything I can to prevent mine rusting away
in my experience, “local garage” and “trust” don’t go together that often, I have heard there is a good Maxda place in Slough but that’s an hours drive from my place
Always flipping difficult to post images on forums - I use Postimage
works every time …
Dinitrol cavity wax it properly, yourself, and then forget about it for another 5 years…
Spray some ACF50 in there, it will displace any water and it’s a great treatment. Clean and easy to use.
Check out Clarke rust remover from machine mart. Product number 059930250 It`s less than a fiver for a litre and you can spray it like water.
A good starting point before any future protection.
Now is not a good time to be waxing you car. As someone has already said you will end up trapping moisture. The best time is in the summer when it is hot and there has been a long period of dry weather. Spray wax into your box sections using a compressor and don’t forget the boot lid!
Gra