Undersealing - Roger Jones
Having not gotroundtuit last year, I'm going to get my Capri undersealed before the winter comes on. Waxoyl and the like have been discussed before, but if anyone has any recent experience of, or fresh opinions on, the best product for the purpose, I'd be grateful.

The story of restoring the Capri from 13 years of dormancy is here:
Undersealing - Dynamic Dave
Waxoyl is only really good for box sections and inside door panels. In areas such as inside the wheel arches it will eventually wash off. However, it is great for revitalising old underseal as it soaks into it and reduces the hardness.

On my previous cars I've always used called Tetroseal underseal, which is made by CarPlan. I once used Waxoyl's brand of underseal, but found wheelarches needed a follow up coat a year later. IMHO, Tetroseal is like the Duracell Bunny - it goes on and on and on....

Undersealing - nick
I used to use waxoyl but went off it as it doesn't penetrate rust very well. I now use dinitrol 3125 and cover it with a coat of body schutz, both applied with an airline. This seems to work well and the dinitrol came out top in Practical Classics' test. The 3125 is really designed for inside box sections etc where some rust may be present hence the need for the schutz over the top to provide some wear resistance. I believe dinitrol to an underseal type product but I've never used it.
The downside is that 3125 is much more expensive than waxoyl but no doubt cheaper than welding in the future. The cheapest I've found 3125 is 4 litres for the price of 3 @ £10 per litre from Mr. Grumpy's Morris Minor Spares in Todmorden.
Undersealing - Aprilia
I've tried Waxoyl on and off since it first came out in the early 1970's. I'm not very impressed with it since it doesn't penetrate.

I saw a test in a magazine (can't remember which one) in which a product called 'Ankor Wax' (from Morris Lubricants) can out better.

I tried some Ankor Wax and it does seem much more penetrative - more like Comma Wax'n Seal (which I've always found good).

Ankor Wax is £13.50 for 5 litres from a Morris' distributor.
Undersealing - Cliff Pope
I stick with waxoyl out of habbit really, and because I always have some left over so it seems a shame to waste it, but then I need a bit more, and so on ...

Some tips on making it work better:
1) Always stand the tin in hot water for at least an hour before use
2) Dilute the waxoyl with white spirit or parafin
3) Clean out the sprayer by squirting neat white spirit through it after use.
4) repeat application every year, but use a more dilute solution subsequently, because the wax is still there, it's the solvent that has evaporated.
5) Clear out drain holes carefully after use. It is very easy to seal water in by blocking its escape route with solidified waxoyl.
Undersealing - dieselhead
I would avoid any of the bitumen based products as they tend to crack with age and the flexure of the body allowing pockets to form that trap salty muck. Also brushed on they look un professional being often used to disguise poor bodywork repairs.
If the surface is dry and rust free polymer based treatments such as 'Gravitex' are far better as they stay flexible. Good used under the wheel arches, spraying on a good coat then use a paintbrush to work it into the joint between front wing/inner wing, front valence/wing and around the wheelarch lip etc. to ensure there totally waterproof. If not using spray equipment or some rust is present better to use a wax based product that won't seal in any rust, then re-treat annually.
If rust does any serious damage it will likely to be around the tops of the front wings,inside the sills, inside chassis rails, back of the headlamps, strut towers, leading edge of the bonnet, inner to outer wheelarch joint, around the spring hangers, door bottoms etc. so these need most attention, although German built Capri's seem less rust prone than earlier cars. These areas are best treated using something like dinitrol's cavity wax that will penetrate the rust and dust that always collects. A coat of heavier wax on the floor pans, underside of boot floor etc, sealing any spot welded joints should finish the job.
Just my 1/2 p worth

Undersealing - Roger Jones
Many thanks for these helpful responses. I've contacted an outfit in Newbury


which specializes in Waxoyl treatment, spraying at very high pressure, and I've asked him to respond to the points raised. I think he is prepared to use products other than Waxoyl.

I'm still looking for places more locally (within 20 miles of Harpenden), but specialist outfits are difficult to find. I'm not going to attempt the job myself, but am still wondering whether it's within the normal bodyshop range of competence (a local bodyshop have said they could do it) or whether it really is a specialist job.

On the German-build front, the Capri was built at the Cologne plant and has always felt as solid as a rock, and the paintwork is still in very good condition -- helped by long-term garaging, of course, but nevertheless pretty impressive after seven years in normal use.
Undersealing - wemyss
The tip from Cliff of standing waxoyl in hot water is a good one.
Do not use any other way of doing this. Many years ago there was a man in the next hospital bed to me with a terribly burnt face and hands. he told me how his son had been heating a tin of waxoyl with a hot air gun prior to use.
The son asked his dad to carry on doing this for him while he did something else.
As he was doing this the tin exploded covering him with red hot oil. The man said his only relief was that it had been him and not the son which I found rather touching.
Undersealing - stan_deezy
Apologies, I know it's an old topic and forgive a total newbie jumping in on this but I have a few years experience of cars, especially older ones and just thought I could share a bit of acquired knowledge.
Have you ever noticed that you never see a rusty M.O.D vehicle? Even second hand they don't seem to rust in the same way as "private" vehicles do?
The M.O.D have a "rustproofing" specification that is so tough that it stipulates that vehicles must be capable of withstanding salt water. What do they use to achieve this level of protection? Dinitrol. I'm not an agent for Dinitrol, just someone who has multi years of experience on old cars and I can honestly say that Dinitrol has been the only product that has truly worked and is easy to apply. You can buy it online and find out more about rust etc at www.rust.co.uk
One other quick tip: don't buy Kurust and all the other fancy rust removers/convertors on the market: go to Machine Mart (or buy online) their own brand Rust Remover (which also acts as a convertor) for £3.51 for a full one litre bottle (!!!). I have used it for a long time and the rust has NEVER returned on any area treated with this (and that's without coating with Dinitrol).
Like I said at the start, I know it's an old topic but this is the time of year when thoughts turn to rustproofing and titivating our old classics so I thought my first post might as well be long and boring :-)
Undersealing - Roger Jones
Thanks for reviving the thread with very useful tips, Stan.
Undersealing - stan_deezy
Thanks Roger, I just thought it useful to pass on experience gained through trial, error and expense! So far all the cars (and boats!) that I've applied Dinitrol to have never needed panels replaced/welding etc. I seem to remember Practical Classics Magazine rating as 100% in one of their group tests too!
Undersealing - Aprilia
Yup, I use Dinitrol. Good stuff.
Undersealing - matstro
Sorry to hi jack the thread a bit........??

I'm very interested to read this thread as I currently have a dilemma!

We bought a 6 year old LWB new shape Frontera recently (worst purchase ever) and its obviously spent much of its life driving up and down a beach - theres very heavy and obvious surface rust on the chassis members and all the associated bits and pieces which is obvioulsy offputting to a potential buyer (we're now selling it on)

My question - I'm thinking of getting the underside steam cleaned and sprayed with some kind of gunk so the rusted surfaces become much less obvious to a buyer.

I'm I thinking along the right lines here...........

Undersealing - steveo3002
ive also found dinitrol to be the best..i dont recal the part number but the one i use is thick brown stuff

one little tip...on cars with factory underseal , i only touch in damged/rusty areas..if you blast the whole underside it can hide problems as much as prevent them

Undersealing - madf
I wash underneath with hose. Allow to dry *2 days.
Use Dinitrol straight on rusty bodywork.
Rust stops.

Blasting off rust/treating with rust proofer is imo a waste of time and money.. Dinitrol delays rusting process significantly. I use the box injection sprays (ex Halfords) for everything. Resist water splashes far better than Waxoyl


Undersealing - Aprilia
Dinitrol do a lovely black undersealing wax - type no. 4195 IIRC. It is applied with a Schutz gun. I pay about £10 litre. You would need 3-4 cans to do a Frontera. Takes a couple of days to dry - leaves a beautiful satin black finish under the car.
Undersealing - prm
Out of interest, where tyre fitters keep jacking the car up, bits of underseal have cracked and fallen off, is it best to leave these areas or touch them up. Thanks
Undersealing - Dynamic Dave
Remove any loose underseal that's been disturbed, wire brush off any surface rust and then make good with fresh underseal.
Undersealing - jc
I've diluted Waxoyl with white spirit until it can be sprayed with a paraffin gun;then leave it to evaporate-works very well.
Undersealing - rg
Daft-ish question - will diluted/warmed Waxoyl work through a garden sprayer type contraption? I've always used a brush and not done box sections. Or do I need a compressor and gun?

Thank-you, PSA, for galvanising my 405/XM...

Undersealing - prm
Cheers all, picked the loose bits off, thers no rust, so brushed fresh underseal on, seems dry enough today so hopefully no trapped moisture.