Technical Oil Sump Rust
- Thread starter Drozich
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Technical Oil Sump Rust
The factory applied powder coating is useless when it comes down to corrosion protection, which is why so many of these sumps fail. Once it's started to rust, it's impractical to remove all the existing rust and paint, and overenthusiastic derusting could in itself cause it to fail.
I'd not use paint in this application; moisture inevitably gets between the paint layer and the metal and it'll continue rusting underneath the paint, which is why the factory coating doesn't last long.
There are various non-hardening rustproofing products on the market, but smearing it with a high melting point grease will protect it as well as anything. Even just a wipe over with a rag dipped in used engine oil every oil change time will do the job. There's no need to remove anything beyond any obvious loose flakes before applying this as it'll soak into any remaining surface rust and prevent further corrosion.
Basically the same comments apply to the rear twist beam; another well known corrosion weakness. If you're planning on keeping the car, I'd check this too.
I'd not use paint in this application; moisture inevitably gets between the paint layer and the metal and it'll continue rusting underneath the paint, which is why the factory coating doesn't last long.
There are various non-hardening rustproofing products on the market, but smearing it with a high melting point grease will protect it as well as anything. Even just a wipe over with a rag dipped in used engine oil every oil change time will do the job. There's no need to remove anything beyond any obvious loose flakes before applying this as it'll soak into any remaining surface rust and prevent further corrosion.
Basically the same comments apply to the rear twist beam; another well known corrosion weakness. If you're planning on keeping the car, I'd check this too.
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Thank you for your advice. We had this issue on an another 500 that we used to own and it rusted through and started to leak so had to replace it completely.
We are selling this car and it was an advisory on the last MOT so wasn't sure what to do about it as I don't want the cost of having to replace it.
TrevC
Established member
This is a pretty rubbish picture I just took of the sump on our 500 that I treated over 2 years ago, still looks pretty sound. I'll post details of what I did shortly.
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TrevC
Established member
So this was how I tackled it. First picture shows it after a good wire brushing. Second one after treatment with Kurust. Number 3 is after a coat of Rustoleum rust converting primer, and finally after painting with Hammerite. I haven't always had such success with Hammerite, but it seems in this case extensive preparation has paid off. Needless to say, I put masking tape over the sump plug for all painting. All this carried out with the car on axle stands. Hope this helps.
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Thank you Trev, that’s a huge help. I’ll do the same
