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      12-16-2020, 11:42 AM   #1
capt_slow
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Slow coolant leak, EGR cooler?

I was poking around my engine bay and noticed my coolant expansion tank was near the low mark, even with a warm driven engine. I looked though my records and realized that

Dec 2019: Last dealer service, expansion tank full (overfilled beyond top half of the tank)
Nov 2020: Coolant level seemed normal on cold engine, level just at the high mark.
Today: Coolant level at low mark warm or cold engine

So in about a year, the coolant level dropped from the overfilled to low, and it dropped from normal to low in less than a month. The last time I touched the system was during my PH test in late October, but all I did was extract, measure, and return to tank.

I inspected all coolant hoses, radiators, and connections, no visible signs of leaks. The dealer did the EGR cooler recall back in Sept 2019 and it checked out fine. I dont have any other symptoms of a EGR cooler issue, no faults, no abnormal smells. What are the chances the EGR cooler is causing the leak?
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      12-16-2020, 12:49 PM   #2
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Mine is similar. Had EGR cooler check, no issues/leaks, checked hoses/fittings and didn't see anything, but coolant level drops slowly over time.
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      12-23-2020, 11:31 AM   #3
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Speaking of leaks, anyone want to hazard a guess as to what was dripping down on my wheel chock from this particular location? That's the right front tire of my 2015 328d Touring... Kinda looks like a "slushy" or "slurpy". Nobody in my household gets those, though!
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      12-24-2020, 10:43 AM   #4
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Quote:
Originally Posted by capt_slow View Post
I inspected all coolant hoses, radiators, and connections, no visible signs of leaks. The dealer did the EGR cooler recall back in Sept 2019 and it checked out fine. I dont have any other symptoms of a EGR cooler issue, no faults, no abnormal smells. What are the chances the EGR cooler is causing the leak?
I don't think the dealer inspection picks up very small leaks in the cooler.
Get an engine oil analysis and look at the sodium value. Ours started to increase at just past 50k while coolant loss was minimal at 1 qt over 10k miles.
We had a steady/slow coolant loss until past 90k when it we lost 1qt in only 1500miles. Sodium made a big jump at the same point.
If you engine oil shows more than 1ppm per 1000miles I would suspect the cooler leak has started. Ours jumped from <1ppm to ~4ppm per 1000 miles when the leak started. Sodium doubled when the coolant leak rate increased past 90k. Wear metals started to rise at that point too.
Sodium returned to normal once the cooler was replaced.
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      12-24-2020, 10:51 AM   #5
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Quote:
Originally Posted by Chukker View Post
Speaking of leaks, anyone want to hazard a guess as to what was dripping down on my wheel chock from this particular location? That's the right front tire of my 2015 328d Touring... Kinda looks like a "slushy" or "slurpy". Nobody in my household gets those, though!
Got any resident rats that like sherbet pops?
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      12-24-2020, 06:57 PM   #6
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Quote:
Originally Posted by catskillclimber View Post
I don't think the dealer inspection picks up very small leaks in the cooler.
Get an engine oil analysis and look at the sodium value. Ours started to increase at just past 50k while coolant loss was minimal at 1 qt over 10k miles.
We had a steady/slow coolant loss until past 90k when it we lost 1qt in only 1500miles. Sodium made a big jump at the same point.
If you engine oil shows more than 1ppm per 1000miles I would suspect the cooler leak has started. Ours jumped from <1ppm to ~4ppm per 1000 miles when the leak started. Sodium doubled when the coolant leak rate increased past 90k. Wear metals started to rise at that point too.
Sodium returned to normal once the cooler was replaced.
Dealer did a pressure test of the system and it checked out fine. They also topped off the coolant. Thanks for the tip! I'll probably keep an eye on the coolant tank level (it's above the tank seam now) and do a Blackstone report at the next oil change.

Quote:
Originally Posted by Chukker View Post
Speaking of leaks, anyone want to hazard a guess as to what was dripping down on my wheel chock from this particular location? That's the right front tire of my 2015 328d Touring... Kinda looks like a "slushy" or "slurpy". Nobody in my household gets those, though!
Could it be road salt?
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      12-25-2020, 07:31 PM   #7
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Quote:
Originally Posted by capt_slow View Post
Dealer did a pressure test of the system and it checked out fine. They also topped off the coolant. Thanks for the tip! I'll probably keep an eye on the coolant tank level (it's above the tank seam now) and do a Blackstone report at the next oil change.
I did multiple pressure test from the first loss of coolant till it went into the dealer for the recall. 20psig/20min, never had any pressure drop. All were performed when engine cold. I suspect the leak opens up when hot, closes up when cold with the help of exhaust gas deposits.
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      12-28-2020, 09:55 AM   #8
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This weekend my low coolant level warning came on. I added 5 cups of coolant to bring it up to the tank seam.

I had the EGR changed at the dealer and shortly after the low coolant warning came on. I found that the small black screw head vent thingy was loose, allowing vapor to escape. I tightened it up and top off the coolant, that was 25k miles ago. I'm right under 200k miles and have not replaced the waterpump yet. No leaks can be seen.

I really hope its not the new EGR cooler
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      01-03-2021, 09:47 PM   #9
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It take only about 20 minutes to check the EGR cooler for leakage.

Just remove the inlet from the cooler to the intake, and look into the cooler for damp gooey soot. if the cooler is ok, you'll just see dry soot.

The BMW inspection TSB:

https://static.nhtsa.gov/odi/rcl/201...8V755-1757.pdf

I lost coolant a couple times and didn't look at my cooler till after the intake had holes burned through it. BMW did repair everything at no cost.
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      01-05-2021, 12:46 AM   #10
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These things can leak from the SCR (Urea) metering unit. There are two soft coolant lines going to it with two quick release joints to hard pipe. Very close to hot exhaust and subject to a lot of vibration. When they dribble, coolant will drop onto the hot aluminum belly pan that is directly beneath the exhaust pipe resulting in no puddle, no smell, just the mysterious loss of coolant and some slight residual markings if you ever pull the pan to access the meter. It's bolted on with security torx so they really didn't want you to be looking up there, lol.
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      01-05-2021, 12:51 AM   #11
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Quote:
Originally Posted by Chukker View Post
Speaking of leaks, anyone want to hazard a guess as to what was dripping down on my wheel chock from this particular location? That's the right front tire of my 2015 328d Touring... Kinda looks like a "slushy" or "slurpy". Nobody in my household gets those, though!
If you have headlight washers and use something like rain-x windshield washer fluid, I'd say it was that. The main supply hose goes right up there and BMW coolant is blue.
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      01-05-2021, 02:44 PM   #12
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Originally Posted by Enabled View Post
Got any resident rats that like sherbet pops?
That's exactly what this looks like! I have had no recurrences so I'm stymied with what it was.

EGR recall was done earlier last year and I would have thought it would have worked all its magic long before I found this!

I'll just have to monitor to see if it happens again. So far I have no other indications of trouble.
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      01-05-2021, 02:48 PM   #13
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Quote:
Originally Posted by MechWatch View Post
If you have headlight washers and use something like rain-x windshield washer fluid, I'd say it was that. The main supply hose goes right up there and BMW coolant is blue.
I do have headlight washers, but haven't added any strange colored fluid. I liked the rat-eating popsicles the best, but all of our wildlife is either much smaller or much larger than a rat!
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