Waterproofing hole in steel

[Theo Markettos]

I've been given a rusty old banger (car). The rustiness is under the wheel arches and I've just been having a go with Hammerite Kurust (chemical that converts rust into something more stable) in order to paint it. Trouble is in scraping off the rusty stuff I discovered two holes in the metal about 1" across where it has completely rusted through.

Since the car is due for MOT in January and I don't know whether it will fail on other things I'd like to patch these holes in the interim to stop further water ingress. So assuming that I paint all the rust around with Hammerite I need something that will either fill up the holes completely, or that I can waterproof bond a patch to the painted surface. I was thinking a piece of plastic (milk bottle maybe) and lots of silicone sealant - is that likely to stick? Would something else be better?

I already have a tube of 'Polycell Squeeze & Seal: Kitchen & Bathroom Translucent' - would that do? It says for indoor use only - does that mean it not going to like outside conditions (freezing temperatures, low setting temp?) or just that it won't last a decade outside? How do external sealants differ?

Thanks Theo

[zymurgy]

You can't really effect a temporary repair without hindering effecting a long term repair at a later date. e.g if you fill the 'cleaned' hole with a load of sealant.

If the hole is on the inner wing, it'll be termed 'structural', particularly so if it's near any steering/suspension mountings.

If outer wing and temporary, you could gaffa tape it until MOT time

Or, MOT the car early (it's due in Jan anyway) and see if the car is worth salavaging.

Welding a steel patch over (gas or MIG) and waterproofing the repair is the only permanent answer for structural bodywork.

For non structural, aluminium mesh or chicken wire and filler will work.

Cheers

Paul.

[Chris Bacon]

Clean inside and outside. Stretch a few layers of sticky tape over the hole, insidethe car. Mix up a little car body filler, and scrape it over the outside of the hole to make a thin smooth layer about

3/16" (5mm) thick. The idea is to make the outside surface smooth in one go so that you don't need to sand it. Stick some paint or underseal on top if you think it worthwhile.

For more help, try newsgroup:uk.rec.cars.maintenance

[The3rd Earl Of Derby]

If this rust and holes are near the structural suspension mounts? this will inevitably fail the MOT and you will be wasting your time putting right any other MOT problems.

Plate welding is the only cure.

-- Sir Benjamin Middlethwaite

[zymurgy]

Oh, and forgot to mention, tack welding no longer allowed, needs to be continuously welded all round.

Cheers

Paul.

[Theo Markettos]

Thanks. I think I'll stick with the gaffer tape solution for the moment (which was all I was really looking for, to stop major puddle ingress). They're at the front of the rear wheels, leading into the cavity adjoining the door sills (don't know if that's structural or not).

Didn't know about uk.rec.cars.maintenance... will ask more things there in future.

Theo (and why aren't there enough hours of daylight at this time of year? 'Apply second coat after three hours' is almost the whole day :-(

[Matt]

Just MOT it now, if it fails then you won't have wasted any money on it in the interim and you know exactly what needs doing to get it roadworthy. Bodging holes with what is essentially crap when you don't know the structural implications is not a particularly good idea.