Carina E's were made up to 1998 (from 1992) I think. So if your one is still in such fine fettle underneath, perhaps it has already been undersealed by a previous owner, possibly the first?.

Edited by badbusdriver on 19/07/2023 at 19:58

I had a car professionally.undersealed 10 years ago. It cost......£700!

It did the job, though. I never had any issues with rust and scrapped the car (an imported Mitsubishi) at 26 years old when the electrics became somewhat unreliable.

You need to find someone that will do it properly - a full wash, steam and scrub, proper dinitrol products and injection into the sills.

"Underseal" traditionally means a thick black rubberised or bituminous underbody paint, popular in the 70's. These are generally now regarded as counter-productive, though they can apparently be effective if carefully applied from new, as in the proprietary "Ziebart" process, and might be useful for spot treating especially vulnerable but accessible areas, such as wheel arches.

As I understand it, the other two main groups of treatments are oil sprays, of which Dinitrol is perhaps the best known and regarded. and wax/lanolin mixes, of which Waxoyl is perhaps the best known and regarded.

Of the commercially available products 'ive only used Waxoyl, and didn't think much of it. At least with the DIY level spray gear supplied, its difficult to apply, tending to clog, and once on it suffers from the same issues as trad underseals,(though perhaps to a lesser degree) in that it has poor rust penetration and tends to skin over, potentially trapping moisture next to the steel.

(This use was probably about 50 years ago, so its possible the stuff has been reformulated and may now be better)

Latterly I have used various improvised oil-based treatments, involving mineral oil (motor or hydraulic) optionally mixed with sunflower oil, with a long squirt of WD40, and lhinned with diesel/kerosene/white spirit until sprayable with a simple/cheap "plant sprayer"

This has good penetration, creeping along weld seems and soaking into unreachable rust. I imagine commercial oil sprays like Dinitrol will share this behaviour. In the unlikely event that I was getting this done professionally I would probably choose someone using a similar product. Thin is better.

While I appreciate that you dont want to DIY, this is really an operation where little skill is required, and (provided you dont spray your brake disks) little damage can be done.

While pro spray equipment and a lift would undoubtedly be a big help, you dont need them to get to your wheel arches, or to spray inside your box sections, and sill interiors (another classic rot point) can be accessed from inside the car by lifting the carpets, making gravity your friend.

Edited by edlithgow on 20/07/2023 at 04:04

The worst thing you could do to an old car that will have some rust lurking is blather it in black underseal. in my experience this traps trouble making things worse (seems to track underneath) that you can't see until it's too far gone.

Myself these days I use Owatrol oil on external surfaces under the car inc suspension - it's a good rust inhibitor that sets to a robust see through resin type finish that resists road spray etc. Available in tins or as an aerosol. Internally I use Dinitrol cavity wax.

Edited by Big John on 20/07/2023 at 20:14