[martopoulos]

So, the last time my car was on a lift, I noticed the metal parts exposed in the undercarriage area are completely covered in what looks like aluminum oxidation or salt. I also see it in the engine bay, as well (see below).

The car is 7 months old and has never been out of SoCal since it arrived in the country. A mechanic showed me another BMW in the shop that was at least several years old that had almost none of it. Any idea what's going on here and what to do about it?

[mdputnam]

I had a similar problem with my RX-7, almost all the aluminum in the engine compartment had a light layer of oxidation. It turned out that there was a microscopic coolant leak that let out coolant vapor (not liquid) when the engine was very hot, for example when shutting down after a track session. The only clue was a very slight smell of coolant if you put your nose right down in the engine compartment. After several years I eventually replaced a coolant sensor buried under the intake manifold and the problem went away.

[overcoil]

Yeah but wouldn't the coolant leave deposit on all the black plastic ? Was there the white deposit on plastic also ?

Is the car near salt water ocean ?

[martopoulos]

Interesting theory (re: coolant), but yeah you would think it would also be deposited on non-aluminum parts, no?

Well, I guess it depends on how close is close. I live 15 miles inland from the coastline, but have made a few trips over the past 7 months to the beach (totaling maybe 5 or 6 hours parked close to the shoreline).

[Pparana]

Salt oxidation, pretty common on unprotected aluminum. You can clean with wd 40, but likely to return.

[martopoulos]

Shouldn't it be protected, though? Like I said, a tech showed me an older BMW that had next to nothing, even though the owner lives in the same region. If everyone's aluminum parts look like this in SoCal, then that's one thing, but if not, then I'm confused about the discrepancy, is all.

[mdputnam]

Salt oxidation? He lives in Los Angles, the closest the car comes to salt is when he drives through Rubio's for fish tacos.

On my RX-7 the only effect of the coolant vapor was oxidizing the aluminum. There was no or minimal deposits on anything else, then again it's a track car and the engine is meticulously cleaned after every race weekend.

[martopoulos]

Originally Posted by mdputnam

Salt oxidation? He lives in Los Angles, the closest the car comes to salt is when he drives through Rubio's for fish tacos.

On my RX-7 the only effect of the coolant vapor was oxidizing the aluminum. There was no or minimal deposits on anything else, then again it's a track car and the engine is meticulously cleaned after every race weekend.

Hah, yeah...

It's helpful to know the vapor only affected the aluminum parts. I think I'll stop by the dealer and bring up the topic to see if they can find a similar leak or else come up with another plausible explanation.

[overcoil]

Unless the type of battery ground has some annode or thingamajig effect on the deposites.

[Pparana]

Originally Posted by mdputnam

Salt oxidation? He lives in Los Angles, the closest the car comes to salt is when he drives through Rubio's for fish tacos.

On my RX-7 the only effect of the coolant vapor was oxidizing the aluminum. There was no or minimal deposits on anything else, then again it's a track car and the engine is meticulously cleaned after every race weekend.

Salt is not only found in the oceans. This could be from any myriad of sources. Could be an industrial pollutant along his drive, could even be in the soap he or someone uses to wash the car.

Your coolant vaporizing could have oxidized the metal or might have been acting as a bridge for electrolysis. More likely electrolysis if the symptoms would come on quick.

[Pparana]

Originally Posted by ScottSinger

Unless the type of battery ground has some annode or thingamajig effect on the deposites.

that would be for electrolysis.

[Pparana]

Originally Posted by martopoulos

Shouldn't it be protected, though? Like I said, a tech showed me an older BMW that had next to nothing, even though the owner lives in the same region. If everyone's aluminum parts look like this in SoCal, then that's one thing, but if not, then I'm confused about the discrepancy, is all.

depends on the contaminant, in any event, oxidation will protect the metal underneath, so I would just leave it.

[martopoulos]

Originally Posted by Pparana

depends on the contaminant, in any event, oxidation will protect the metal underneath, so I would just leave it.

True, but I'm worried that if it's this bad after only 7 months, that by the time I'm ready to sell, it'll look like this:

http://strongarmbrand.com/SitePages/...eStrongArm.jpg

[gtmax500]

For what it's worth, I live literally 5 seconds from the Chesapeake bay and only have a fraction of the oxidation you have. Granted, the bay is only about 15 ppt salt (average ocean is about 35 ppt) but still its very salty air. I did also wonder if my oxidation was normal.

[martopoulos]

I took the car into the dealer today. They checked for leaks, etc. and found none. They sent pictures to BMW NA, who replied saying that the level of oxidation is normal even for the age of the car. I still don't understand how it can look like that after 7 months when much older cars in the same area have even less oxidation. Nothing I can do about it at this point, though.

[mdputnam]

If this is the problem, I'm not surprised the dealer didn't find anything, my RX-7 symptoms were:

1. Passed a visual inspection, no signs of a leak - The stuff was vaporizing as it escaped from an almost microscopic crack in a coolant sensor hidden from view under the intake manifold.

2. Passed a coolant dye test using a UV lamp, again there was no visible seepage.

3. Passed a leak down test. - The leak was very slow and only occurred when the engine was very hot, i.e. I never detected any appreciable loss of coolant, although the coolant was replaced every year.

The only sign that there was a leak was the corrosion and the very faint smell of antifreeze after a track session when I pulled into the pits and raised the hood. The smell would go away about a minute or so after raising the hood.

To check for a similar situation I would suggest you drive your car for at least an hour and get it nice and hot, pull into a garage (to keep out of any breeze) and keep the hood down for about 10 minutes (to allow the vapor to accumulate). Make sure the radiator fans do not come on! Then open the hood and sniff around the engine compartment for a slight antifreeze smell.

[martopoulos]

Originally Posted by mdputnam

If this is the problem, I'm not surprised the dealer didn't find anything, my RX-7 symptoms were:

1. Passed a visual inspection, no signs of a leak - The stuff was vaporizing as it escaped from an almost microscopic crack in a coolant sensor hidden from view under the intake manifold.

2. Passed a coolant dye test using a UV lamp, again there was no visible seepage.

3. Passed a leak down test. - The leak was very slow and only occurred when the engine was very hot, i.e. I never detected any appreciable loss of coolant, although the coolant was replaced every year.

The only sign that there was a leak was the corrosion and the very faint smell of antifreeze after a track session when I pulled into the pits and raised the hood. The smell would go away about a minute or so after raising the hood.

To check for a similar situation I would suggest you drive your car for at least an hour and get it nice and hot, pull into a garage (to keep out of any breeze) and keep the hood down for about 10 minutes (to allow the vapor to accumulate). Make sure the radiator fans do not come on! Then open the hood and sniff around the engine compartment for a slight antifreeze smell.

Good tip-- I'll try that. Never smelled antifreeze before, but I read it is sort of maple syrup-like, so I'll sniff for something like that...

[overcoil]

This is my 2 year old 235 which lives about 12 miles from the closest salt water estuary.

[martopoulos]

Originally Posted by ScottSinger

This is my 2 year old 235 which lives about 12 miles from the closest salt water estuary.

Looks like substantially less build-up. Thanks.

[Maynard]

Do you use commercial car washes? I've heard some of them use pretty harsh chemicals.

[martopoulos]

Originally Posted by Maynard

Do you use commercial car washes? I've heard some of them use pretty harsh chemicals.

Sort of. I've been going to the self-service, manual car washes that are so common on the west coast. It should just be high-pressure soap and water-- no acid wash or similar, if the description is to be believed.

[Pparana]

Originally Posted by martopoulos

Sort of. I've been going to the self-service, manual car washes that are so common on the west coast. It should just be high-pressure soap and water-- no acid wash or similar, if the description is to be believed.

More than likely the wash, probably cheap soap, yet effective since it contains alkaline phosphates.

Same issue with the guys coolant, Japanese cars contain phosphate in the coolant, euro cars do not, unlikely of you had a coolant vapor leak that would oxidize the aluminum. Plus rx7, rotary, leaks and burns everything then stops running at 50k after burning 100k of gas.

At high pH, the 'passive' aluminum surface dissolves as Na2Al(OH)4 (sodium aluminate). This reveals 'active' metal underneath, which reacts with the phosphates in the water to form aluminum phosphate. Sodium aluminate reacts with sodium phosphate to form sodium aluminum phosphate. Sodium aluminum phosphates precipitate out of the water, and deposit onto the sites along the surface of the aluminum leaving these powdery spots.