[Closed] Undersealing a cheap car - worth it?

Also came across some more short-term rust-proofing products as commonly used on motorbikes, namely ACF-50 and XCP Rust Blocker (which comes out better in this thorough-looking test: https://www.bennetts.co.uk/bikesocial/reviews/products/the-best-motorcycle-corrosion-protectants/tested-xcp-rust-blocker-corrosion-protectant-review). Thoughts on using these maybe a couple of times a year on a car chassis? Probably easier to apply.

i don't think i'd bother. if you wanted to keep it 'forever' and it could be guaranteed to be done properly, then i possibly would. I don't know if they're known for rusting out or not, but a bad undersealing job is worse than not doing it I would say. My little connect has 5 years on your van and it wasn't undersealed - it has had some welding done for the last MOT but cost buttons, and it hadn't needed any for the first 16 years of it's life.

The guy that looks after my Stepwagon does undersealing for £150, £120 for smaller cars. Considered DIY but not worth the time or mess for that. See if there’s any car import places locally, they’re likely to have someone they use.

For 150 quid I'll be surprised if your getting any more than a steam clean and a spray with what ever product.

Two issues.

Already established rust .

Areas of chassis not fully dry.

Most product do a wonderful job of allowing both to develop un noticed.

New cars it's worth while .

But on a 58 plate your just hiding the mess from.the MOT man imo.

When I did van it was steam clean , a week to dry , worst of the rust off with a wire wheel , fertan then the underseal.

Still not perfect .

The landy got a strip down to the chassis and full going over with the needle gun before primer and paint.

Final point is - if it's a car prone to rust like say a Mazda 3 or a transit.....you are only delaying it it's still coming for you

if it’s a car prone to rust like say a Mazda 3

Mine is 13.5 years old and all the signs are is that it is about to implode from underneath. There is no surface rust on the car but it's like Shane MacGowan's teeth underneath.

🙁

Cheers for the replies.

Most product do a wonderful job of allowing both to develop un noticed.

Yeah, did wonder about this. I've been to look at a couple of classics before and the I was always wary of what underseal might be hiding.

That could be mark in favour of the ACF-50 type products? They're not permanent and as far as I can see are thin and clear so wouldn't hide anything.

New cars should come sealed, and as others say, unless the job is done on a completely clean and rust free car then it's likely just hiding the problem.

My Honda is 18 years old and still in good shape underneath with no body rust either. If you want an older car for a decent length of time it's worth getting something well made.

ditto the new car sealant - I've not had a problem with rust as a car killer since we moved onto late 80's/early 90's cars

not had citroen or mazda though, but have had several alfa 147 - they were famous for tinworm last century

As per Trail rat above - knock off any rust scabs, get any trapped mud/dirt out from wheelarch areas then Fertan or equivalent followed by Dinitrol. Dont bother with Waxoyl - its crap.

Be prepared to get it in your hair, over the drive way, on brake discs, on the cat/dog, the hot exhaust, coating your lungs.

Its a crap job {former Defender owner - now Mk7 Transit} there is more to life.

I'd not use undersea or schultz

Id use a wax or look at frost restoration products and their dinitrol range

Mine is 13.5 years old and all the signs are is that it is about to implode from underneath. There is no surface rust on the car but it’s like Shane MacGowan’s teeth underneath.

Rear seat belt mounts are a favourite.

But you'd be surprised how bad a car has to be to fail mot....and it's already majorly structurally failed by the time you fail the mot toffee hammer.

From experiance I expect under normal use and treatment a car to last between 12-18 years before rust takes hold.....up here. Down south YMMV

I wash the underside of the car more in winter than I wash the top of the car the whole year.....

The last car I owned that suffered any sort of rust was built in 1993, and was 10 years old when I bought it.

I didn't think rust was an issues any more, the old things I've heard rusting were grey imports that don't get undersealed in their native markets.

There are a 100 things that can kill of an old banger. Rusting out the floor is only one. I would keep the money in your pocket and wait for something to fail.

didn’t think rust was an issues any more

Your right when it comes to the bits you can see barring early dacias.

Underneath rust is still a common issue.

Terminal rust still an issue for folk who run old cars.

Is this still a thing people do? The last time I heard of anyone undersealing a car it was my uncle on a 1977-plate Fiesta.

it’s like Shane MacGowan’s teeth underneath.

He's had 'em done now, you know.

Is this still a thing people do?

No because on the rental cars most folk seem to drive they hand them back to the cars owner/next owner to deal with.

Gone are the days when a cars seen as a long term purchase and treated as such.

Coupled with the bits that the owner sees -typical owner having not bothered to look behind the sills....not rusting anywhere nearly as bad as in 1977 they don't bother their arse.

Definitely not the old under seal mix that was used but if this is a bit of a keeper and in good nick now, then we steam clean and then waxoil Underneath. As above Frost make good stuff but we use Waxoil, have used it mixed with diesel in the past but now just wax oil. Probably 40-50 if you do it yourself. Our local village garages do it for 80 for small cars and 110 for bigger ones.

not rusting anywhere nearly as bad as in 1977

Yeah, that's where I was coming from. Technology has moved on, unless you're buying bargain basement marques / models I'd have expected a ten year old car built in 2010 to be in considerably better shape than a ten year old car built in 1977.

I sprayed a micra once a year for 12 years with hydraulic oil and it certainly protected it. Mind you I had free access to the ramp and oil so had it done in an hour or so.
Then it took a few weeks to drip dry enough to allow it on the drive.
Its something that I no longer need to do and somehow I don't miss it.

I’d have expected a ten year old car built in 2010 to be in considerably better shape than a ten year old car built in 1977.

You'd be right but some folk have cars beyond 10 years . Between 12-18 years is when it starts to be an issue

There are still cars with serious rust issues , Ford and Jaguar ad anything Mazda they touched are the worst for terminal rot in sills, Kia subframes rot out but can be replaced, BMW 3 series , Mercedes any before 2005 and some after, VW golf front wings, basically you need to research individual models .
MOT testers are warned during test of individual model rust issues so they do go and check in the problem areas.
Can spay/brush chainsaw bar oil thinned onto existing under seal and rust when it’s dry to keep it flexible and water resistant.

Between 12-18 years is when it starts to be an issue

Fair point.

I wouldnt bother for all the good reasons already posted. If it looks good the now I'd be happy enough, if it's rusting already its rearguard action work and id rather see whats going on.
My last banger was an 04 astra diesal, engine was good but the underside was looking worrying in the tinworm department to say the least (highlands car). I got shot to an astra fanatic who got 2 and a half years out of it before it finally succumbed though so it probably looked a lot worse than it was. Interestingly it looked very tidy for its age but if you looked in the front bulkhead it had plenty rust, a common area for it.
I once heard it suggested painting wd40 on underneath, you can buy in bulk apparently. Always sounded iffy to me but the guy was adamant it was worthwhile. Anyone done that?

Wd40. Absolute waste of time.

Be gone before you got to the other end of the car.

Spent diesel oil. Nasty stuff don't spray it don't get it on you .... But does work at stopppig the rot.

Only do it if you work on your own car though. Your mechanic won't thank you and put down a tarp /let it dry before you go drive it.

I probably won't bother then. I certainly won't be chucking any money at it, and I know from experience what a crap job Waxoyl is to apply, but I could get over it if it was worth it. I might look more into the ACF-50 type stuff. If it's cheap enough, an hour with it on ramps spraying the obvious bits isn't going to hurt.

I once heard it suggested painting wd40 on underneath, you can buy in bulk apparently. Always sounded iffy to me but the guy was adamant it was worthwhile. Anyone done that?

See the chart in the link in my second post. They did it, but it doesn't stack up well against most of the other products they tested - though better than Muc-Off Motorcycle Protectant!

Gone are the days when a cars seen as a long term purchase and treated as such.

This 🙁 You rarely hear undersealing mentioned any more, but I think that probably says more about most people's attitude to maintaining anything these days. "You have to maintain stuff? But it's cheaper just to chuck it away and buy a new one!" Don't worry, future generations will pay for it :-/

it’s worth getting something well made.

While the sentiment is true..... It's blind luck a Honda got to 18. I wouldn't rank them highly in the anti rusty stakes at all.

For a 58 bingo. Keep the front of the rear arches and the rear of the lower sills clean and there very little else prone to rusting out double quick on then.

Probably front subframe would be next to go

For a £2k car not worth the bother.

Something special like a 911? Maybe if its a keeper but really you are just delaying the inevitable if you use it all weathers.

Just be careful what you are buying in the first place, I.e. Not a coastal or Scottish car (salted roads more of the year).

I bought a 2004 Berlingo in 2014 from a coastal northern Scotland town and brought it to an east coast north Scotland town and got another 4 years out of it without it being rotten at all......

I sold it to someone for a car to use while they modernised they house doing tip runs etc.

It's still on the road today.

For a 58 bingo. Keep the front of the rear arches and the rear of the lower sills clean and there very little else prone to rusting out double quick on then.

Good stuff, cheers.