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Underseal.

edwin

Enthusiast
Messages
901
Location
Lichfield
Hi Guys. what's the advice on underseal . The car we have is a '72 4L, which is very clean underneath and rust free, direct from Southern France. There are various methods available, ranging from waxoyl upwards. The benefit of your experience would be most welcome. Thanks Edwin
 
Hi Edwin,as you say there's a lot of brands of underseal-stuff available.over here in Norwayland we have lots of bad experience as they salt
the roads using Tons after Tons of that dreaded corrorosive salt on our roads all winter long.
In my opinion whatever brand you go for Use the Thin stuff-ONLY.The heavy more covering stuff is just Too heavy trying to cling on upside
down under the car-eventually it Will sag and let go under its own shear weight leaving pockets/bubbles on the bare metal surface giving
moist and damp/water inside the "Best" possible condition for rust to develope to an extrem extent. And the worst of it is still looks good
from a simple inspection...
I'm using 2 cans (400g) refreshing the thin cote underneath every spring to keep a good cover and to keep it soft/elastic so it wont dry out
and start cracking...jacking one side up at a time you'll have nice access whole job is about an hour, remember to cover hair/nose/mouth.
I'm using bitumen-based stuff (I tried wax-based but it didn't last as long as bitumen) -Most imperative is using THIN stuff only //-Reid.
 
That's true - the problem with any thick waterproof coating is it can fail and still look good on the outside while it is trapping water on the inside. Best thing is to use something that falls off as soon as it fails so it can't trap water.

Just paint would do the job. It's not abrasion resistant, but it's trapped water that kills cars not surface rust.

I once worked on a new car undersealed with the black waxoyl stuff that never dries. I got very messy. Makes a car horrible to work on.

You get exactly the same problem on house windows - modern plastic paint holds water in and won't let it out again so things rot. Linseed paint works for windows as it's kind of an oil. It's helped keep my 100 year old windows in reasonable condition. I've been using it on metalwork outside with success. One of these days I'll try it under a car.
 
Bilt Hamber Dynax UC (clear) or UB (brown) aerosols are well reviewed and are good to use. Ends up a semi-hard wax but starts off thin spray so gets in everywhere. Also useful for electrical connectors, bolts etc. to stop corrosion. Expensive but large cans, and worth it. Handy to have it right there for when you spot a missed bit or an area of damage.
 
Hi guys and thanks for the comments and suggestions. My MGB is just painted, and it was done 32 years ago as part of a body off restoration, and its still good, but being open topped it only gets used in clement weather. The R4 having a tin top offers wider scope, but would not get used in snowy/icy/salty weather.
The underside is completely clean. There is some paint, but coming from somewhere near carcasson, it has never seen bad weather, and there is just some mechanical abrasion. I have not got a pit, have some wheel jacks, so the method needs to be simple, and achieveable for a 70 year old. If I was doing a body off restoration then the paint and all the protective coats would be the way I would go. But starting from here, where the car has an amazing patina which I would like to retain, I do not want to disassemble the car, and I am leaning towards the dynax wax. I understand the comments about thin verses thick and heavy. We all have seen cars where there is something bullit proof under there and then a bit is missing and you can see that most of it is 2mm away from the metal with water behind. So if you use the Dynax, how do you stop a build up making a thick coat. Does it evaporate at time extends, and then you just do a quick top up spray? Do you spray into the cap and paint the areas that need precision with a small brush?
 
Bilt Hamber Dynax UC (clear) or UB (brown) aerosols are well reviewed and are good to use. Ends up a semi-hard wax but starts off thin spray so gets in everywhere. Also useful for electrical connectors, bolts etc. to stop corrosion. Expensive but large cans, and worth it. Handy to have it right there for when you spot a missed bit or an area of damage.
hi Adam and thanks for your comments. I have some questions.
The underside is completely clean. There is some paint, but coming from somewhere near carcassone, it has never seen bad weather, and there is just some mechanical abrasion from road gravel. I have not got a pit, have some wheel jacks, so the method needs to be simple, and achieveable for a 70 year old. If I was doing a body off restoration then the paint and all the protective coats would be the way I would go. But starting from here, where the car has an amazing patina which I would like to retain, I do not want to disassemble the car, and I am leaning towards the dynax wax. I understand the comments about thin verses thick and heavy. We all have seen cars where there is something bullit proof under there and then a bit is missing and you can see that most of it is 2mm away from the metal with water behind. So if you use the Dynax, how do you stop a build up making a thick coat. Does it evaporate as time extends, and then you just do a quick top up spray? Do you spray into the cap and paint the areas that need precision with a small brush?
 
Hi Edwin -the Bilt Hamber Dynax comes with a longish pipe (like wd40 does, but larger bore), so can be used in channels/tubes etc with good effect - it's quite a vigorous concentrated spray with the pipe. A mist emerges from the inner pipe-ends of the rear suspension (EDIT - sorry, I am recalling my Scimitar!) when you spray in the outer end, so it's getting all the way through those! Without the attached pipe, the spray is evenly spread and somewhat like spray-paint in use; you can lay down a wide fine mist or a drench quite easily depending on distance from the car and times hovering over the area. Sounds like the UC (clear coat) would be good over your exceptional underside! You can see what is happening then as well. The spray can seems to be able to work at almost any angle and I've used them under several of my cars on ramps or axle stands with no problems (except getting dripped on sometimes). Hope this helps!

If the spray is too heavily applied, it will drip immediately but it seems to level itself quite well and dries to a softish coat after a few hours (but stops running very quickly). It pretty much stays where you spray it, but isn't thick like stonechip so is probably difficult to build up excessively in just one coat. I've not tried brushing it to touch up - there's no need when one quick spray does the job!
 
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