Yes - and no.

Most modern cavity protection is thick and grips to vertical surfaces. It needs to be heated to thin and is then sprayed within the cavity using a 360º spray head. This coats all the surfaces and flows down where the water gathers too.

If you block the drains and fill the cavity with a treatment it will only flow to the bottom but not cling to vertical surfaces.

I'm not sure if I read your post right but if you block the drains at the lower edge of the sills you can't use the upper drain tube to fill the cavities. This drain tube should lead out under the car.

In years gone past old mechanics used to fill sills and cavities with used engine oil to hold rust at bay. Modern treatments are more effective and less dirty.

Get a good rust converter such as dinitrol RC900 and spray it into the sills via every access hole you can find, including the drain holes, door strikers, sill cover mounting holes, behind the seat belt towers etc. Let it do its thing for a day or two. Then repeat with your chosen cavity wax. And to finish off go round your drains after a day or two and make sure they are totally unblocked.

 

It's going to require and waste a hell of a lot of cavity wax.

Much easier to just use somethign like Dynax S50 which includes a hose to ensure everything is coated as evenly as possible. This cavity wax is also designed to 'creep' into crevices and seams to ensure everything is coated.

 

If you have a hardtop on permanently, rain can't get into the sills can it? As the inlets where the rain usually drains into off the soft top is now inside the cabin.

 

If you have a hardtop on permanently, rain can't get into the sills can it? As the inlets where the rain usually drains into off the soft top is now inside the cabin.

they can't get in from there, but water/damp can still ingress from under the kickplates, and by the doors, it's not a sealed area

 

I did exactly that with a lot of old engine oil after I cut all the rust out and welded in new panels.

FYI it leaks out under the seats into the car and takes about 3 weeks to completely stop dripping from the sills. And it stinks. And it was super messy.

I reckon it did help little.

I wouldn't do it again.

 

The huge Dintrol 5 litre treatment I did to my '89 dripped out for a few hours, then I had to clear all the drain holes again afterwards as it sort of 'sets' and ends up like a grease, it smelt like boot polish for a week or two afterwards inside the car but doesn't smell of anything now.

It's a filthy job even done with the correct stuff, I don't think blocking everything up to fill it with something like oil would be a good idea all in all. Oil is designed to run and not set, cavity wax is designed to get everywhere, then the solvent which is in it evaporates (causing the smell) and it sets where it is permanently.

 

I figured it would leak out everywhere although not in the cabin maybe I need to wait for another batch of useless inspiration to pop into my head and you never know I may come up with the perfect solution

Then again.....

Thanks for all the replies

 

I drilled a hole each side in the door jamb just above the door catch(1/2" I think). Plugged the drain holes with blue tack. Used a syringe/pumphttp://www.screwfix.com/p/hilka-oil-suction-gun-500cc/12527 to spray oil up on the inside of the rear wheel arches(about 2-3 pints each side). Drove around the block accel and braking, nice sloshing sound. Then put drain trays under the drain holes and let it out.

Once it had almost stopped dripping laid out some cardboard under the sills to catch the rest. That was about 4 years ago. Didn't get any oil out any where else except from btm sill joint.

On the original Minis the rear subframes didn't last, the front ones went on and on. The fronts benefited from a covering or misting of oil the back ones didn't.

Malcolm

PS Don't leave a trail of oil or you may have an accident yourself but more importantly some poor devil on a motor bike may be a victim of your actions.

 

Ahhhh where's No1Birdman...