Tomorrow I’m planning on finally changing some parts I’ve been postponing forever to do. To change them I’ll have to remove the timing belt cover, exposing the side of my engine block. It looks like it has accumulated dirt and what looks like some rust (only on the crankcase, I’m guessing it’s made from cast steel and the cylinder block made of some aluminum alloy) and if possible I’d like to improve the looks of it. There’s also some superficial rust on the alternator belt pulley I’ll have to disassembly.

block rust

pulley rust

For now I’ve been thinking about spraying some decarbonizer, using some metal brushes and maybe a 80 grit sand paper to remove the rust, than using a paint brush to apply rust converter (phosphoric acid), let it act a while, remove excess and reassembling. Since I’ll remove the water pump and thermostatic valve I could also use the steel brush to try to remove rust from the inside of the cooling system (but I can imagine how it could also turn to a bad idea). Because of the temperature I don’t think using paint designed to cover rust is an option.

For the alternator pulley, I thought about just lightly using the steel brush on the rust areas and adding the rust converter. Since that one is easier to access, I could remove it again later and maybe repaint it. I’d wash the product away before reinstalling it because I think it could damage the belt.

Does it sound like a good idea or is there a better way to do it? What about the cooling system ducts, should I stay away from it?

  • 2
    In most cases, rust on an engine is just an eyesore. What you are suggesting doing here is one of those situations (IMHO) where if it isn't broke, you probably don't want to fix it. You may cause more issues than you are curing. Nov 8, 2019 at 16:50
  • 1
    I agree with @Pᴀᴜʟsᴛᴇʀ2 on this one, if you scrape off the rust it means you expose more metal to the air and you'll just get more rust
    – GdD
    Nov 8, 2019 at 17:06
  • 1
    I use rust conversion spray, then you can paint it any color you wish after the converter has dried.>>>>amazon.com/VHT-SP229-Rust-Convertor-Can/dp/B002NUABUO
    – Moab
    Nov 8, 2019 at 19:26
  • 1
    Power washing is a good way to get it done, but you need to be wary of your electrical bits & pieces. Nov 8, 2019 at 22:21
  • 1
    @IanC no need for High temp, I only use that on exhaust manifolds. I use regular ol engine paint as a rust preventive after converting the old rust.
    – Moab
    Nov 8, 2019 at 23:39


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