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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?

MeltingDog
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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.

Pᴀᴜʟsᴛᴇʀ2
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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.

Matt
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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.

trond hansen
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  • 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. – Pᴀᴜʟsᴛᴇʀ2 Feb 23 '20 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. – trond hansen Feb 23 '20 at 13:48
  • What is water if not two parts hydrogen and one part oxygen. And you want that concentrated on the iron parts? – Pᴀᴜʟsᴛᴇʀ2 Feb 23 '20 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. – trond hansen Feb 23 '20 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 '20 at 14:32
  • @Pᴀᴜʟsᴛᴇʀ2 In the absense of oxygen, water does not corrode iron, see for example this video demonstration. No, the oxygen in the water molecules do not attack the iron. Boiled water in a sealed system might actually be a pretty decent option. On the other hand, it will dilute the coolant (which I'm pretty sure has oxidation inhibitors in it) that remains in the system... In the end, I'm not sure if it's a good idea or not, but your reaction seems a bit harsh. – marcelm Apr 01 '20 at 14:56
  • @marcelm - When someone suggests something which will damage vehicles and ultimately might cost people money, I don't believe there is a "too harsh". The advice given in the answer is bad advice, pure and simple. I will concede the tests in the video show no rust in certain circumstances, however, the two circumstances where rust did not occur would not be present in a vehicle engine (sealed with no water whatsoever or water with encapsulating fluid to prevent the absorption of air into the water). Leaving the block empty with some antifreeze is far better than dumping plain water into it. – Pᴀᴜʟsᴛᴇʀ2 Apr 01 '20 at 15:27