Should I have my car's rear axle area painted with underseal?

[Accy cyclist]

The other month after I'd had my car serviced, the mechanic said my car had a fair amount of rust around the rear axle. He said he'd wire brush/sand paper it down and paint it with underseal for about £40, before the bad weather sets in and we then have metal rotting salt on the roads. I haven't had this suggested to me for decades, since the 1970's/80's even early 90's days of cars that suffered badly from rust. I'd like to see this supposed rust before I say yes or no. If I said to the mechanic I'd like to see it first it'd look like I didn't trust his word and maybe I don't.🤔 He said that If I didn't have it done the rear axle could collapse and then it's cost a lot of money to have it welded etc. My car is a 10 year old Fiat 500. It doesn't have any rust on the bodywork. Should I go ahead with it, or just accept that old cars still rust and if I pay for that, the mechanic will find another problem to get more money out of me?🤔

 

[Brandane]

. I haven't had this suggested to me for decades, since the 1970's/80's

If this was the 70's/80's, your 10 year old Fiat would have long ago turned into a small pile of orange filings.

£40 doesn't sound too much for a bit of preventive maintenance and peace of mind.

 

[biggs682]

If you asked me to see it and i was the mechanic i wouldn't mind showing you and explaining why i suggested it

 

[Cycleops]

After reading a few post about rear axle corrosion it seems your mechanic might have a point. The government even warn about it:
https://mattersoftesting.blog.gov.uk/why-its-important-to-check-for-corrosion/
Heres a post from someone who has your same model 500:
https://www.honestjohn.co.uk/forum/post/index.htm?t=103675

 

[mustang1]

I googled fiat rust axle rust but the problem is if Google knows you are searching something, it goes out of its way to find it for you. Ordinarily that's a good thing (it's what we want from a search result) but at other times, it feels like the result is skewed so the problem may not be as big or as common as Google makes it out to be.

Having said that, as @biggs682 says, maybe the mechanic can show you. I would take a look out of interest, and not as a way of "hey I don't trust this mechanic". I would have thought an MOT checks for these things but I REALLY don't know. It would be prudent to give it a look at least or if that's understandable, then perhaps a second mechanic's opinion.

 

[Jameshow]

Yes anything beginning with a F get it rust proofed!

Indeed to do my transit van really. My van has offered me the use of his outside 4 poster lift.

 

[Bonefish Blues]

Yes if he's going to do it properly for £40.

No if has going to give it a bit of a brush and then seal in the rust.

 

[wafter]

Firstly, I'd we wary of using "underseal" as you don't want it sealed, you want a forgiving, semi-liquid skin that will allow moisture out while preventing further corrosion. Underseal is fine on new, bone dry cars from the factory, not on old vehicles and especially not (IMO) applied at a time of year when it's damp and you may well be sealing in a lot of additional moisture.

Secondly, tbh the rear axle (does it even have a proper one..? ) is probably the least of your worries as it should (Fiat cost-cutting notwithstanding) be fairly substantial so less of a concern regarding the effects of corrosion. Of course it's always good to protect everything, however I'd be a lot more concerned with thin panels that have rust traps, so the bodywork / arches / floorpan etc.

If you're bothered I'd be more tempted to wait until the baking hot middle of the summer then get the whole underside / box sections treated with waxoyl / Bilt Hamber products. While not entirely without merit I think just doing the axle on its own would be a bit of a token gesture towards preserving the car.

 

[fossyant]

For £40 get it done with waxoyl etc. I've done all our cars, even from relatively new. The 10 year old Aygo we bought was a bit crusty on the rear subframe, so I cleaned it up and waxoyled it - some folk never clean the underside of the car - a simple hose down removes a lot of the salt.

I'm assuming you can't climb under with a tin of paint, so £40 sounds good to me. It's about £8-£10 a tin - may need two.

 

[Cletus Van Damme]

I'd get it done Accy, maybe with different products as mentioned above as underseal just covers the problem. When they say rear axle they mean the rear suspension beam.

I've got an 11 year old Mazda 2 which aren't the best for rust. Recently I rust proofed most of the car. It was going where yours is the rear suspension beam, rear chassis legs and was bad under the rear wheel arch liners and a little under the front ones. The products I used were Dinitrol as I've read its better than Waxoyl and I've used it before on an MX5. Cleaned it first then sprayed everywhere with Dinitrol ML, this is just a really thin cavity wax, way thinner than waxoyl, because of this it "creeps" into cavity section really well. After it dried then applied Dinitrol HS 3125 to the impact areas, this is a self-healing wax, a lot thicker than ML, but it doesn't set like an underseal does.

These 2 products cost about £20 each for a litre to be used with a shutz gun, 1 would cover that easily. The rear suspension beam is a fairly substantial piece of steel (thickness), I'm sure it will last for ages if treated and years if not (dependant on its current state). If it was mine and it was only going there, I'd buy some HS 3125 and get them to rub it down and spray it and pay them £40. You could get Waxoyl cheaper but I've read it cracks after a while, as I've read it fully dries out. This stuff has still not dried after applying it around 4 months ago, still feels tacky. There's all kinds of products available. Some used engine oil would be better than nothing though.

HS 3125 Cavity Wax

 

[SpokeyDokey]

Ivm not sure what any professional could do for £40 inc' materials.

Can't me much awry tbh.

 

[Jody]

Ivm not sure what any professional could do for £40 inc' materials.

Can't me much awry tbh.

Bet it doesn't involve much prep work

 

[I like Skol]

Rusty 10yo Fiat...... New bike car time 👍

 

[Accy cyclist]

Thanks for the replies folks! I wonder if I could go to one of those 'big' tyre centre places and ask them to put my car on their hydraulic jack, or whatever they're called, so I could see underneath?🤔 Would they charge me just for that, or could I blag it and say I think the brake pipes might be corroded etc. When they see they aren't (well I hope they aren't) I just say thanks for looking, then drive away.

 

[fossyant]

Thanks for the replies folks! I wonder if I could go to one of those 'big' tyre centre places and ask them to put my car on their hydraulic jack, or whatever they're called, so I could see underneath?🤔 Would they charge me just for that, or could I blag it and say I think the brake pipes might be corroded etc. When they see they aren't (well I hope they aren't) I just say thanks for looking, then drive away.

For £40 let them do it. an you get down and shine a torch under, you'll soon see.