M50: rinse cooling passages and chambers in the block?

[make it easy]

Before I took the engine out of the car I drained the coolant from the block and it was a very clean green stuff, no rust or signs of corrosion, no impurities. Upon closer inspection of the drain plug 07119919228 I noticed that the flat end of the bolt was rusted and not flat at all. I didn't pay too much attention until I removed the engine out of the car and looked through the drain hole..

Inside the drain hole I saw a rusted blockage, blocking 90% of the drain. Now it made sense why the drain process was so slow, yet so much coolant came out. Only later I realized that the blockage is in fact the remainder of the drain plug! That;s why the plug itself was rusted at the bottom and wasn't flat but rather looked broken.

The next step was to remove the remainder. I tapped lightly on it with a punch tool and a hammer to "shock" it a bit, therefore aiding the extraction process. As soon as I did that, my punch tool went straight through the blockage: that remainder of the bolt was just 1 mm thick. So I cleaned the drain hole from all that rust and sludge, but I am pretty sure some of it went inside the block while I was 'running the extraction operation', and I don't that stuff in there.

So my goal is to try and get that dirt out while the engine is out, on a rotating stand and easily accessible. That rusty sludge is loose so I don't want to use any additives or cleaning solutions. All I want is RINSE those cooling chambers and passages, hoping that the rusty sludge will come out naturally with fluid through the drain plug.

I am thinking to just buy some coolant concentrate and mix it with <gotta find out what exactly> in like a 30/70 proportion and pour it down another coolant hole that's at the back of the engine, on the top. And hope that I will be able to just rinse that sh*t out through the drain hole.

I wanted to run it buy you guys first, maybe you have some better advice. Also, what type of water should I be mixing with the coolant concentrate? Is there a better way?

Cheers!

[LockDots]

If you're just flushing, use regular hose/tap water. Once you're ready to leave coolant in you should use distilled water paired with either BMW coolant or Pentofrost (OE Coolant).

[make it easy]

If you're just flushing, use regular hose/tap water. Once you're ready to leave coolant in you should use distilled water paired with either BMW coolant or Pentofrost (OE Coolant).

Doesn't tap water have negative effects on cooling system? The engine will be out and dry for another month, I am afraid to start a corrosion or smth that might be irreversible in the future. What r your thoughts?

[LockDots]

Yes. Chances are the previous owner used that in conjunction with generic green coolant which also causes corrosion.

Doesn't tap water have negative effects on cooling system? The engine will be out and dry for another month, I am afraid to start a corrosion or smth that might be irreversible in the future. What r your thoughts?

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[Eric93se]

Putting water in there will in no way remove or flush out the rust. You would have to use a chemical for that and let it soak a while (follow instructions). Also green antifreeze does not cause rust at all, over time it will become acidic and then it will attack the metal, but that is only from stupid car owners that don't flush the fluid on a schedule.

You can use this if you really want to, and yes stick to distilled water when your done.
https://www.amazon.com/Evapo-Rust-Or.../dp/B00M0TLQ66

[LockDots]

Putting water in there will in no way remove or flush out the rust. You would have to use a chemical for that and let it soak a while (follow instructions). Also green antifreeze does not cause rust at all, over time it will become acidic and then it will attack the metal, but that is only from stupid car owners that don't flush the fluid on a schedule.

You can use this if you really want to, and yes stick to distilled water when your done.
https://www.amazon.com/Evapo-Rust-Or.../dp/B00M0TLQ66

This. I should've been more specific about the acidic qualities of the green stuff. Not sure of the blue stuff is immune to that but it's all I've ever used and never had an issue with rust. Then again I flush at least every other year.

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[make it easy]

Putting water in there will in no way remove or flush out the rust. You would have to use a chemical for that and let it soak a while (follow instructions). Also green antifreeze does not cause rust at all, over time it will become acidic and then it will attack the metal, but that is only from stupid car owners that don't flush the fluid on a schedule.

You can use this if you really want to, and yes stick to distilled water when your done.
https://www.amazon.com/Evapo-Rust-Or.../dp/B00M0TLQ66

To clarify. The goal is to remove the pieces of rust/sludge that fell into the block through the drain hole while I was cleaning the drain hole. That dirt is floating loose and is not stuck to the inner walls of the block. Why would I need any chemicals? Thanks!

P.S. The drain hole got rust on it's walls and threads from the stupid drain plug that rusted pretty badly. I unscrewed the plug super easily, just like any other drain plug, but its rusted parts stayed inside the drain hole, so I had to scrape, and clean them off. Some of that mess fell inside the block while I was cleaning. One would think 'OMG, I can only imagine the condition of the engine if the plug itself was that bad'. But no, all the fluids are super clean and the engine ran great (knock wood). I have no idea how the plug rusted so badly!

[Eric93se]

Well I guess you could get an inspection camera that can go inside the hole to check. Because if the inside of the plug rusted to the steel of the block then there is probably a coating of rust inside as well. The fluid may look clean but if it's old then it can become acidic and that's when it starts attacking the block. You could just leave it alone and change the fluid earlier because the anticorossive chemicals in the antifreeze can become depleted.

[make it easy]

Well I guess you could get an inspection camera that can go inside the hole to check. Because if the inside of the plug rusted to the steel of the block then there is probably a coating of rust inside as well. The fluid may look clean but if it's old then it can become acidic and that's when it starts attacking the block. You could just leave it alone and change the fluid earlier because the anticorossive chemicals in the antifreeze can become depleted.

The engine will be out for another month or two before I can start the car, while I replace all the seals, gaskets (except for HG), bring vanos back in shape and do the auto-manual swap. I am storing the engine in a unheated garage (Canadian winter to consider).

So I'd like to go with a route that will induce no damage or negative effects to the cooling pathways as well as the head gasket. I took a peek through the drain hole and the inner walls of the block seem to be dark grey in color with very little white sludge spots here and there. But no rust.

I need to create that fluid 'flow' to rinse it efficiently while the engine is out and not running. Nothing except for tap water comes to mind. But I am afraid that tap water might be bad. Unless I fill the engine up with the coolant right after the 'tap water rinse and flush', and let it mix with whatever tap water is left in the system, maybe? And then once all the walls are all covered with coolant, flush that again, a day or two later?

[LockDots]

The engine will be out for another month or two before I can start the car, while I replace all the seals, gaskets (except for HG), bring vanos back in shape and do the auto-manual swap. I am storing the engine in a unheated garage (Canadian winter to consider).

So I'd like to go with a route that will induce no damage or negative effects to the cooling pathways as well as the head gasket. I took a peek through the drain hole and the inner walls of the block seem to be dark grey in color with very little white sludge spots here and there. But no rust.

I need to create that fluid 'flow' to rinse it efficiently while the engine is out and not running. Nothing except for tap water comes to mind. But I am afraid that tap water might be bad. Unless I fill the engine up with the coolant right after the 'tap water rinse and flush', and let it mix with whatever tap water is left in the system, maybe? And then once all the walls are all covered with coolant, flush that again, a day or two later?

What about using a coolant cleaner or radiator flush type of chemical? those are usually recommended to stay in the engine for a while to let it work so I'd imagine it would help prevent rust as well in the meantime since there wouldn't be just air in the block.

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[flyfishvt]

Read this. It explains the eletrolysis issue in very simple terms. https://www.hotrod.com/articles/keep...-electrolysis/

Flushing with a garden hose won't cause any issues while the engine is on the stand. The only corrosion will be some very very minor surface rust because the cooling passages are exposed to air while it's on the stand. While it's true that tap using water to fill thecooling system can cause corrosion you aren't filling it. With the engine in it's normal vertical position 99.99% of the water in the block will drain out the drain hole. Any tiny amount that remain won't be sufficient enough to cause any issues once the engine is installed. The distilled water and corrosion protection in the coolant will be more than enough protection.

You're afraid of damage happening while the engine is out. This is needless fear. You're overthinking the situation.

It's very common to find that drain hole plugged with a paper thin crust when you remove that drain plug. I've seen it on almost every m5x engine and lots of other people have too. It does not indicate any damage to the engine.

[make it easy]

Read this. It explains the eletrolysis issue in very simple terms. https://www.hotrod.com/articles/keep...-electrolysis/

Flushing with a garden hose won't cause any issues while the engine is on the stand. The only corrosion will be some very very minor surface rust because the cooling passages are exposed to air while it's on the stand. While it's true that tap using water to fill thecooling system can cause corrosion you aren't filling it. With the engine in it's normal vertical position 99.99% of the water in the block will drain out the drain hole. Any tiny amount that remain won't be sufficient enough to cause any issues once the engine is installed. The distilled water and corrosion protection in the coolant will be more than enough protection.

You're afraid of damage happening while the engine is out. This is needless fear. You're overthinking the situation.

It's very common to find that drain hole plugged with a paper thin crust when you remove that drain plug. I've seen it on almost every m5x engine and lots of other people have too. It does not indicate any damage to the engine.

Thanks flyfishvt for your reply! Can you write any thoughts on the following:

- After the coolant is flushed, the internal surfaces of the cooling system are still covered with a tiny layer of the mix, giving them some sort of corrosion protection.
- Rinsing the block with tap water will remove that layer. Now the tap water will be on the walls, which will accelerate corrosion (by insignificant degree, but still).
- To prevent this, it would be a good idea to follow up with another fill right to the top with the coolant mix, leaving it for a day or two and then flushing the block again, effectively recoating the surfaces with the coolant.

Just wondering if the benefits outweigh the time spent for this last extra step in a long term. I am really not sure how long the engine will be out, in a colder environment (unheated garage in winter). I got weekends only to work on it and the Christmas holidays aren't helping =)).

Cheers!

[XnWarden]

Water isnt like oil. It doesnt leave a coating. It evaporates into the air. Sometimes it will deposit minerals or other chemicals onto the surface when it evaporates. Any mineral deposits that might have taken place will dissociate into the New antifreeze solution.

If you are one of those paranoid OCD types like my friend, you could run some coolant thru the block to "flush" it. But like I always tell him, you are over thinking this.

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