[AHall]

Originally Posted by armoredsaint

the dealer just pressure tested my expansion tank and said zero drop in pressure, told me the white residue is from the cap that is designed to release pressure and fluid will come out. i am still somewhat skeptical, but at least there's a record of my check. they did replace my brake fluid a few months early when I asked if they could so I don't have to stop by in the fall.

Seems like if the cap is in deed designed to vent, it would vent to a safer location like a tube similar to the AC condensate line.

[Maverik259]

I think the issue is the caps are venting too early. Prior to their designed pressure. Based on where all my residue was it seemed likely to be coming from the cap and not the tank but the dealer replaced both for me and I haven’t seen a spec of white since (February).

I know some did have failed tanks though too.

[WayneM3]

Well this is unfortunate. He replaced his coolant tank with the new one and it leaked too.

[frozenRedm5]

I've contacted manufacturers like Morosco to see if they can develop an aluminum tank as they've done for other BMW platforms, but it's a no go. Although they are aware of the issue. Maybe they just need to hear from more people to justify it.

[afo818]

Originally Posted by WayneM3

Well this is unfortunate. He replaced his coolant tank with the new one and it leaked too.

Damnit finally had a sense of relief lol

[pmsteinm]

The spark plug procedure has you remove the expansion tank (altough I don't think you have to). Maybe we just amend that to "replace expansion tank" every 30k miles when you do the plugs.

[Aronis]

I was under the impression that the coolant tank for the intercoolers was a separate circuit, but after more research, the flow of coolant goes to both tanks as the cooling circuit for the intercoolers is continuous with the main cooling system. So all the 'leaks' have been from the large main tank and no one has reported (perhaps I did not see it anyway) any leaks from the smaller tank. That tank is similarly positioned in the engine bay and exposed to the same heat. Just food for thought. Is that smaller tank a magic tank? LOL. (magic grits reference).

Mike

[pbonsalb]

I don’t think any engine coolant mixes with the intercooler coolant. One system operates at maybe 200F and the other at maybe 100F. There should be less pressure in the intercooler system in addition to the lower temperature.

[pmsteinm]

They are indeed separate:

[HerkHealer]

This also happens on the M550. My expansion tank cap was leaking/venting to the point where I had dried coolant (white stuff) everywhere. I took it to the dealer, they did the pressure test, and no drop. I ended up buying a new cap and it seemed to help. I have not seen the white dried up coolant since then.

[hookson]

We are currently working on solution for M5/M8 platform coolant tank leak. This cover will make sure that even if your tank leaks, it will not flood your injectors. The coolant will drip through the frame rail.

[hookson]

I should have first batch here in the US in the end of August.

[afo818]

Originally Posted by hookson

I should have first batch here in the US in the end of August.

Group buy?

[hookson]

Originally Posted by afo818

Group buy?

We most likely gonna have them in stock on constant basis. But I can take reservations if anyone is interested 👍🏻

[afo818]

Originally Posted by hookson

We most likely gonna have them in stock on constant basis. But I can take reservations if anyone is interested 👍🏻

Cool brother will most likely take one night as well give it a shot

[Aronis]

Originally Posted by pmsteinm

They are indeed separate:

Attachment 3240583
Attachment 3240584
Attachment 3240591

Yes, that was the diagram, I was thinking about the Turbo coolant lines, my bad. That makes more sense.

Mike

[NoMods]

Originally Posted by HerkHealer

This also happens on the M550. My expansion tank cap was leaking/venting to the point where I had dried coolant (white stuff) everywhere. I took it to the dealer, they did the pressure test, and no drop. I ended up buying a new cap and it seemed to help. I have not seen the white dried up coolant since then.

same here, the dealer pressure-tested it about 3 weeks ago and no problems, i may just get a new cap too.

[pmsteinm]

I just noticed in the diagram above they have the arrows pointing in the wrong direction for the engine auxiliary radiator.

[pbonsalb]

I am not sure the diagram shows incorrect flow direction for the auxiliary engine coolant radiator. It is auxiliary and may serve to further cool the main radiator cold side output and feed that back into the main radiator hot side input. But I don’t know for sure that is how the system works.

[Stlthnmrdrd]

ive also had white residue around my coolant tank time to time and went to the dealer 2 times to check. They told me no leaks were found.. im guessing its the cap venting like people were mentioning, but i wonder if the aluminum cap ind sells prevents the leaks

[AHall]

Originally Posted by Stlthnmrdrd

ive also had white residue around my coolant tank time to time and went to the dealer 2 times to check. They told me no leaks were found.. im guessing its the cap venting like people were mentioning, but i wonder if the aluminum cap ind sells prevents the leaks

Try it out and let us know.

[pmsteinm]

Originally Posted by pbonsalb

I am not sure the diagram shows incorrect flow direction for the auxiliary engine coolant radiator. It is auxiliary and may serve to further cool the main radiator cold side output and feed that back into the main radiator hot side input. But I don’t know for sure that is how the system works.

I see what you are saying but it shows cold water coming in and hot coming out. So, I'm pretty sure it's a typo. It is interesting that the diagram in the S63TU guide looks completely different because the aux coolers are charge air only. And that version also had water supplied to the DME. But the S63TU4 guide says "vehicle dependent" which of course makes more sense.

Either way the whole systems has lots of complexity...4 electrical pumps and 1 mechanical, complicated thermostat and sensors.

I'll probably do the thermostat at 100k miles like I did on my wife's E90...the thing is complicated enough that it won't last forever, and I'd rather replace it early enough to no get stuck and enjoy it vs replacing it right before selling or something. Not sure about the electric water pumps. I did that on the N54 as well but that was back when BMW had a bad rep for cooling systems. Not so sure now.

And depending on how things go for others I'll replace the expansion tank.