The cooling system in my car is full of rust. It's quite corroded. I have drained and flushed the system but need to wait for some parts to be delivered in 2 - 3 weeks.

The system is now empty of fluid and I am worried about oxidisation. Should I be concerned?

3 Answers 3


Basically, leaving your cooling system dry and letting it sit will cause you no issues. Don't run the vehicle (obviously) without coolant. If you run it too long, this can cause issues.

If you have an aluminum block, there's no chance for corrosion. The aluminum will have already formed a protective barrier, which inhibits corrosion. If an iron block, you'd have to let it sit for years in the open air (outside of a building) for it to corrode enough to cause any issues. Seeing as how the cooling system is inside the engine, there's no real chance for it to corrode. Any coolant which remains in the system will also help prevent any corrosion.

Really, there's no real reason to fear leaving your cooling system dry (or mostly dry) for a few weeks, or even a month or so. You'll most likely have it all back together well before any damage would occur.


It can be. There is a risk that any old sludge/scale that attached to cooling surfaces will dry out and potentially fall off. Once liquid is refilled this debris can block small passages.


Where air moisture and metal meet there will be corrosion.

If possible fill the cooling system with warm water(warm water contains less dissolved gasses)and put the radiator cap on.

This will limit the oxydation a little,oxydation will still happen but at a slower pace.

This is not something you have to do but the thing is 2-3 weeks might grow to be 4-6 weeks and if this is the case you might want to protect the cooling system a bit.

  • This is terrible advice. You don't know what type of engine/vehicle the OP is driving. If aluminum block, there's absolutely no worry about corrosion with an empty cooling system. If an iron block, water is going to be worse than air, because the moisture is what causes the corrosion in the first place. Water is concentrated moisture, which means the possibility for more corrosion. Argh. Feb 23, 2020 at 13:33
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    @Pᴀᴜʟsᴛᴇʀ2 the reason it is called oxydation is because of oxygen if one can keep the oxygen away from the metall no oxydation can happen.but you are right there is no need to do this if it is an aluminum block engine. Feb 23, 2020 at 13:48
  • What is water if not two parts hydrogen and one part oxygen. And you want that concentrated on the iron parts? Feb 23, 2020 at 13:53
  • @Pᴀᴜʟsᴛᴇʀ2 i realy hope no electrolysis is going on in the cooling system of the car because this will be a major problem,the only way to get free oxgen from water is to add energy. Feb 23, 2020 at 13:57
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    Pretty sure oxidation occurs underwater but at a much slower rate. Either way I think you guys are mostly splitting hairs. If I was op, I would only drain the coolant system if it was leaking. Else I would leave it alone until I was ready to work on it.
    – narkeleptk
    Feb 23, 2020 at 14:32

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