Classic cars forum & vehicle restoration.

[bob2]

my dad regularly (like once a year) applied underseal to the underside and dinitrolled the rest and occassionally he'd also throw old engine oil or linseed oil in the doors and apertures and the little green mini was completley immaculate at 20 years old and still is now cause tough I have resprayed it, it never has had any welding done!!

[Jim.Walker]

Underseal is a whole new topic and my experiences of it as an ex-MOT tester are largely negative. In particular I remember a 105E Anglia wonderfully undersealed from new and with very little signs of rot.
Testing spring hangers and chassis could only be done by GENTLE tapping with a small hammer and noting the sound. Nothing sounded questionable on this car.
One week later the owner re-appeared and said he was reporting me to the Ministry. It seemed the offside rear spring, front hanger had "disappeared" and the spring end had come through the floor.
I asked him if he would allow me to see the car so I could answer Ministry questions. He agreed.
There was no sign of the spring hanger, only a hole. I looked at the other side which looked pristine with its underseal. "That one is OK" said he. I remembered that both looked the same at MOT, so I gambled and fetched a big hammer (naughty!) and took a mighty swipe. The hanger EXPLODED, leaving a matching hole in the chassis and floor and rust scale over a quarter of an inch thick on the garage floor.
I never saw him again. He left rather abruptly clutching his MOT Certificate before I could even consider whether I had the right to confiscate it. Nor did the Ministry turn up.
All I can add is BEWARE OF WHAT UNDERSEAL CAN HIDE ON OLDER CARS!
Jim.
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Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[Phil - Nottingham]

Actually Rover P5's and earlier and some later cars used Bittac underseal as standard which was a mi=xture of asbestos and pitch. Thus hardened after a coupe, of years and carcked to allow moisture and consequnet corrosion to wreak havoc underneath.

It was only good for deadening when new but that advantage was soon lost as holes appeared in sill/floors, D posts and inner wings
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Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2

[Salopian]

Phil
How right you are - underseal is quite dreadful stuff and usually conceals substantial rot in my experiance over the years. The trouble is once its there and cracked as it always does its the devil to get off and get oil/preservative on.
Of course for MoT a good brushful improves and strengthens poor welding or even pop rivets and brazing no end!!!!!!!
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Jonathan Butler
Alvis SD 12/50 1928 MG TD 1950

[bob2]

I knew you'd say that but in my case underseal was not applied once when the car was new and forgotten about but every year the underside of the car was given a good clean with old petrol and paraffin and then another layer of underseal, I removed almost 3/4 of an inch (thickness) of underseal from the subfames and the paint underneath was still as fresh as when it was new.
That said however in malta the weather is much more gentle to the cars and we do not have any snow or ice thus no grit which eats the cars over there in the uk!!
I checked the whole floor when the car was dismanteld and sprayed and there wasnt the least amount of rust anywhere, the inside of the floorboards and sills still have the original factory paint on, the rest of the car was resprayed in 2 pack to match but only beacause of a dented door, dented boot and a small dent in the bonnet and the paint was impossible to match 100% so the decision was taken to respray the whole car including the engine bay, boot and inside.

I do not use underseal myself but instead cover the underside of my every day car in a mixture of waxoil and gear oil, must re do it this year since its been about 6 or 7 years since I did it last!!!
Will also spray this mixture in the hunter's chassis rails, probably will do this saturday if I find hal an hour to spare!!

[Phil - Nottingham]

In the UK I really think underseal does more harm than good - a properly applied paint finish can be easily and quickly cleaned, trouble spots spooted before they have spread and rectified.

It is not just salt laden grit that does the damage its condensation in semi closed box sections which may have salt in them that will rot steel way inside a year. If this can be sealed before it gets rusty then there is chance to prevent rusting but once it is there it will win in the end unless car is alwsy kept dry and warm. Not possible here except on rarely used museum pieces for looking at rather then driving them
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Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2

[bob2]

I still think that you'd need something to seal off the elements on the underside paint on its own is not good enough, a mixture as I mentioned in my earlier post should do the trick, box sections should also be filled with it though!!
I beleive that a clean once a year and re application should do the trick though and not only for the underside but in all apertures and wherever water might get trapped!!
After all its only a days worth of work whereas if you intend keeping the car but let it deteriorate its much more work than that to rectify the damage!!

[baconsdozen]

I live in lowestoft and my cars are parked within a few yards of the sea,getting a good dosing of salt spray when the weathers bad.
I welded my transit extensively a few years back and have had to reapply a gungy oily mix under it a few times since.I think the problem with oil is that it washes off from road spray and unless reapplied regularily it ceases to provide protection.
Old underseal that has become dried out and brittle is worse than useless,it loses contact with the metal it's supposed to be protecting and water gets in the cracks,unseen it then creeps into the spaces and rots out the metal.A thin oily mix sprayed on top might penetrate some of the cracks but isn't going to drive out all the water in there and the only cure for old underseal is to remove it completely.
I remember a guy bringing in a MK2 Zodiac he was selling for me to weld some years back,on one side the box members and inner sill were holed,on the other the sill had been replaced and covered with thick underseal.Curious that something didn't look right I scraped some off to reveal a sill made of wood.When in conversation with the owner he also mentioned he'd used an grinder of some sort to "remove the deep pits in the brake pipes" I decided not to repair what had the potential of being a death trap.
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Thirty years selling imperial hand tools for old machinery(Now happily retired).

[Nic Jarman]

In the interest of the wellfare of your cars - move.
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1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush

[baconsdozen]

But then I don't get to see this every morning.
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Thirty years selling imperial hand tools for old machinery(Now happily retired).