[wonho]

This is some great discussion. Thanks everyone for chiming in.

I checked the reservoir again this morning. The stick was floating at an appropriate height. And there was no additional residue on the stick after having washed most of it down by adding coolant yesterday.

I smelled it – nothing pungent; same old, mild coolant smell. I don’t quite know what rust smells like.

I dipped a rolled piece of paper towel into the reservoir to catch the top layer of the residue if there were any, and the attached pics show all I got (not much really). So it seems that it wasn’t really infested with the crap. Might have just been some carry-over crap from the older coolant before the flush.
I touched it and smudged it around. It did feel greasy. It looked like oil too. There may be a leak somewhere, but if there are any, then they must be pretty minor. Otherwise, this oil may be a result from small contamination while replacing the oil filter housing gasket.

I am scheduled for an oil change and a coolant flush on Thu at a very reputable BMW shop (not dealer). This issue will specifically be addressed. (I just had a chance to talk to him on the phone, but preliminarily it sounded nothing serious at all.) This time, I will go to 50% BMW coolant, 50% distilled water, and 1x 500ml bottle of MoCool. If the residue issue persists, I will address it to the dealer then with my CPO warranty, upon which I’m expecting that the dealer will perform the cooling system pressure test. Also if currently-used engine oil shows a decent amount of frothy yellow stuff upon draining, I will most likely take further action to rectify the problem. I’ll keep you guys updated.

To summarize all our discussion and some of my findings from reading your informative links, etc.:

- I currently have 90% distilled water and 10% MoCool (for those who might have mistaken that I only have water). (Recommended is 95%/5%, but I went a little more precautious with 10%.)

- MoCool is in fact purple according to the spec sheet attached.

- I have no cooling issues as of yet. Without coolant, the water+WW actually performed better in terms of cooling (no limp modes at the track this year, stock everything, stock OC, typical oil temp at track: 240F, typical coolant temp at track: 190F).

- WW does have anti-corrosion, -freezing, -boiling, and lubrication properties, but not nearly as effectively as a typical Propylene Glycol coolant.

- Water has higher tendency to boil than coolant, hence increasing cooling system pressure. Our enclosed cooling system may not be okay with such increase in pressure, we don’t know for sure.

- Water’s higher tendency to boil can also cause steam pockets within the engine, in which state the heat transfer capacity drops significantly. This may cause the engine to over-heat locally and cause failures, while the coolant temp measuring probe might be elsewhere, oblivious to the problematic areas.

- In racing environment, two of the reasons for using water without coolant are: (1) slippery track upon leaks; (2) better cooling properties.

- I still have warranty, and I’m kinda tired of headaches. I wanna just stick with OEM recommended and if problems show up later, then I’m just gonna knock on BMW’s door. My car is not a racecar, and I really don’t wanna go the whole nine to fix its genetic cooling problems. If any coolant-induced limp modes show up at the track again in the future, then I’m getting something else (E36 M3, early NSX, FR-S, etc.).

(Okay that last one was a rant )

[brusk]

Originally Posted by ajsalida

Again I may be wrong but my limited understanding of how this works is the following:

Water only works great as coolant until it doesn't. It begins to boil in pockets near combustion chambers where metal is hottest. It has a higher vapor pressure than water/coolant mix so this can cause leaks/overflow. Once level gets low things cascade quickly and you end up with a lot of air pockets around the combustion chamber, things then go bad real fast.

On a turbo car esp w/tune & higher boost I personally would not run pure water in my own car. As I said water wetter is fine.

There was an SCCA tech bulletin out a while ago about one spec class engines melting with only water as coolant. This was on very hot days and racing conditions.

I am curious to find out what the OP's car has going on, maybe this will shed some light.

edit: a system designed for higher pressures a water-only coolant system would generate is fine (like in NASCAR, say). I do not know what the design limits on a stock BMW coolant system are, or when you might exceed them.

It seems very unlikely that you can melt any part of the engine. Obviously the first thing that would happen if your running over hot temps is something on the coolant system will blow such as the radiator cap as it should. Next is usually the head gasket but occasionally you will get plastic things that will melt such as a distributor cap (seen it on a mid 80's MR2 that overheated) or plastic intake manifold. If somehow the engine is still running with any of those problems then the problem was behind the wheel.

[JamesM3M5]

Originally Posted by ajsalida

Again I may be wrong but my limited understanding of how this works is the following:

Water only works great as coolant until it doesn't. It begins to boil in pockets near combustion chambers where metal is hottest. It has a higher vapor pressure than water/coolant mix so this can cause leaks/overflow. Once level gets low things cascade quickly and you end up with a lot of air pockets around the combustion chamber, things then go bad real fast.

On a turbo car esp w/tune & higher boost I personally would not run pure water in my own car. As I said water wetter is fine.

There was an SCCA tech bulletin out a while ago about one spec class engines melting with only water as coolant. This was on very hot days and racing conditions.

I am curious to find out what the OP's car has going on, maybe this will shed some light.

edit: a system designed for higher pressures a water-only coolant system would generate is fine (like in NASCAR, say). I do not know what the design limits on a stock BMW coolant system are, or when you might exceed them.

Nobody is arging to run pure water. It allows too much corrosion and has no lubricant properties that the pump seals need.

Localized boiling is not a problem with increased system pressure. It is also further reduced with surfactants like MoCool and WW, which reduce surface tension and allow better conduction of heat from the metal to the water.

The whole point of the argument to run little or no ethylene gycol is that water is a better heat exchanger. Arguing boiling point is secondary to exchanging the heat in the first place, which is where the "scientists" in the other link you posted were missing the point. An example from one SCCA document where someone "melted" an engine on pure water also is missing a lot of other critical details.

[ajsalida]

Originally Posted by JamesM3M5

Nobody is arging to run pure water. It allows too much corrosion and has no lubricant properties that the pump seals need.

Localized boiling is not a problem with increased system pressure. It is also further reduced with surfactants like MoCool and WW, which reduce surface tension and allow better conduction of heat from the metal to the water.

The whole point of the argument to run little or no ethylene gycol is that water is a better heat exchanger. Arguing boiling point is secondary to exchanging the heat in the first place, which is where the "scientists" in the other link you posted were missing the point. An example from one SCCA document where someone "melted" an engine on pure water also is missing a lot of other critical details.

Well let's agree to disagree and I'll keep running 50/50 in my car. Let me see if I can find that SCCA doc. just for the record.

edit: see attch.

[JamesM3M5]

Originally Posted by ajsalida

Well let's agree to disagree and I'll keep running 50/50 in my car. Let me see if I can find that SCCA doc. just for the record.

edit: see attch.

You're also missing the point. The empirical evidence trumps theoretical properties. You can think what you want, but you are disagreeing with actual empirical evidence from hundreds of racecars running around tracks all over the world show reduced coolant temps when running 95% water / 5% additive. This is also rigorously documented for our specific application in the track forum.

That document also points to multiple points that were neglected causing those engine failures. Additionally, piston damage comes from detonation, not water pockets boiling locally in the head.

[Streetluger06]

I raced spec miata for 3 years and everyone ran distilled water and water wetter mixed. It provides the best cooling. As far as corrosive properties, I am not sure, we never had leaks or pump failures though.