[capt_slow]

Background: Prior to getting the redesigned EGR cooler in the 21V-907 recall, my UOAs had consistent signs of a coolant leak. After the recall, that seemed fixed.

The latest UOA came back with another possible coolant leak. Levels jumping from 9 to 30 in just 6K:

Sodium reared its ugly head again, with this sample featuring another notable increase in that area. This report does hold good news too in the wear metals which are all a bit lower than before, so we didn't find signs of increased wear to go along with sodium, and there's hardly any potassium (the other coolant marker). Still, it's looking like there may be coolant reaching the engine oil, so we'd avoid longer intervals even with the TBN still showing some active additive left. Check back in 6,000 miles or so for another look at sodium

Coolant levels did drop in the two years and 13K since the recall was done.

Sept 2022, 59K: On the dealer service drive right after recall was done. Likely cooled engine.


Nov 2024, 79K: Cooled engine



Interestingly, BMW revised the recall SIB with below verbiage. It makes me wonder if it's related to what I'm seeing.

IMPORTANT: The cooling system must be properly bled after replacement of the EGR cooler.

Failure to perform the venting procedure could introduce air pockets in the cooling system for the EGR cooler (or coolers) that will damage the new EGR cooler and possibly the intake manifold.

While the rest of the car is out of warranty, the EGR cooler extended warranty still has 2 years left.

[ssf556]

Is there a procedure to properly make sure the coolant system has no air in it?

[capt_slow]

Originally Posted by ssf556

Is there a procedure to properly make sure the coolant system has no air in it?

The official procedure is the vacuum fill method. Below video is for a B58. AFAIK the steps involving the HVAC dont apply to the N47 since the latter is a mechanically-driven pump while the former is a electrically-driven pump.

[capt_slow]

Here's a blurry shot of the fins. Should that clump on the bottom right be of concern?

[TurboWeasel]

If it's as metallic as it looks in the picture, then yes, it is a concern.

[capt_slow]

Dealer checked the car out and nothing seemed wrong. Pressure test of the coolant system came back normal, the EGR cooler had no signs of a coolant leak, and a 1K test run didnt show a drop in the tank. I also sent a virgin sample of my oil to Blackstone and sodium levels were 38ppm (UOA was 30)!

Sure enough, the sodium in your used oil sample was from an additive in the oil. Sodium read 38-ppm in this sample, which is consistent with the 30-ppm reading in the last used sample from your 328d. This level is a little different, though, as are some of the oil additive elements (most notably molybdenum and boron). At each oil change, some of the old oil (and anything in it) carries over. The last batch of Top Tec 4600 you got had different additive levels. It looks like they changed the formula, so we'll expect similar sodium levels going forward.