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MG Midget and Sprite Technical - underbody prep?

Hi guys, I know this must have been covered a thousand times and you prob think its a stupid question! but i need a step by step idiots guide to protect underside and arches.


1)The underside of the midget is in fantastic condition and has a thin layer of what looks like black underseal, which was applied over 20 years ago! Do i scrape this off rub down and use rust encapsulator or just paint over the top?

2)What is the best product to use? dont really want waxoil under the car so should i use a rubber product or por 15, shults etc?

Oh and i plan to do a full waxoil treatment on box sections etc, but which product Waxoil, denitrol, other?

there seems to be a massive choice of products and wanted to know what you experts think, or have used yourselves?


thanks for any help steve.


s j knox

Steve, it might be worthwhile to remove a small section of the underseal to check the condition of the steel. I am in the process of a partial restoration on my frogeye and the floor looked excellent until I took an angle grinder equiped with a wire brush to it! Most of the floor was fine but I found where there was rust underneath the underseal would scrape off easily whereas if the steel was good it stuck like the proverbial to a blanket! If you find dodgy bits, my advice would be to get it really cleaned up, paint with a zinc based primer followed by an OIL based chassis paint (2 coats of each). Hammerite is too brittle, as I believe is POR 15, some of the epoxy paints get a good write up, but oil based is cheap and works well.
I believe the advice now is to use a stone chip resistant sealer under the vehicle, as this is designed not to crack and break up under the impact of road debris. With that and 2 layers of paint it should keep the underside for another few years.
If your underseal is truly OK then it is probably best just to leave it or maybe clean it and spray over with stone chip underseal.
Practical Classics are doing a long term test on cavity waxes and at the moment the leader seems to be "Korrosions-schutzfett" which unfortunately has to be heated during application. This was followed by "Nuxodol 700" in aerosols and then "Bilt-Hamber Dynax S50" which can be bought in bulk. This was in the March 2011 edition of PC if you can get hold of a back issue, it also covers surface treatments.
Hope that helps a little,
Graham.
Graham P 1330 Frogeye

thanks for the advice graham!
s j knox

I would agree with Graham. I have just restored my midget and the floor looked like yours I attacked it with a paint scraper and where the stone chip fell off grinded back to metal painted and under sealed but where the stone chip is stuck to the metal I would leave it alone and apply more stone chip.
C Carter

The easiest way to remove old underseal is with a heat lamp and a paint scraper, then finally a wipe with kerosene to lift any remaining residue. Once you have removed all of it you can easily tell where rust is and repair/replace it.

Here is what the bottom of one looks like after replacing the OEM underseal with some modern stuff, which is then painted over. The "bead" finish of the underseal doesn't come out too well in this photo, but you can see it clearly in the front wheel well, where the light is reflecting off of it.

Norm


Norm Kerr

careful you don't get too carried away scraping off the underseal. Here's what mine looke dlike after I'd gone a bit too far :-)




graeme jackson

I am with you on that one Graeme! My car was/is made entirely of structural underseal!

Malcolm
M Le Chevalier

They don't make underseal like they used to :+))
Graham.
Graham P 1330 Frogeye

It appears that (at least some) stonechip isn't waterproof, according to the spec sheet I got from the paintshop.
I went etch, zinc, cellulose gloss, stoneschip, cellulose gloss.

Still good after 7 years.

If you heat the stonechip in a pot of boiling water before use it goes on more easily but you can also add thinners to it to get a smoother surface. Has anyone ever tried rubbing it down?
rob thomas

If its anything like the crud on the bottom of my car then you would need to cut down the amazon in order to make enough sandpaper to rub it down. It clogs up anything and everything in an instant!

Cheers,
Malcolm
M Le Chevalier

I got all the crud off a radiator cowling by leaving it on the bonfire for a while.

Not to be recommended for the whole car ;o)

Dave
D MATTHEWS

This thread was discussed between 18/06/2011 and 21/06/2011

MG Midget and Sprite Technical index

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