[capt_slow]

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?

[FaRKle!]

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.

[Chukker]

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!

[catskillclimber]

Originally Posted by capt_slow

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.

[Enabled]

Originally Posted by Chukker

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?

[capt_slow]

Originally Posted by catskillclimber

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.

Originally Posted by Chukker

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?

[catskillclimber]

Originally Posted by capt_slow

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.

[OneLapper]

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

[chrism9852]

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.

[MechWatch]

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.

[MechWatch]

Originally Posted by Chukker

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.

[Chukker]

Originally Posted by Enabled

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.

[Chukker]

Originally Posted by MechWatch

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!

[capt_slow]

It's been about 5500 miles since the coolant bottle was last topped off and I think there is a drop in the coolant level. Ended up topping off the tank with Zerex G48

Coolant level before: 35588 on the odo, cold engine, topped off by dealer


Coolant level after: 41142 on the odo, cold engine

[capt_slow]

Blackstone just returned me my UOA, sample had about 8K miles on it. Oil was LiquiMoly TopTec 4600. Sodium levels were at 57, which they said was higher than normal and might be a sign of a slow coolant leak.

This is a good report on the whole, with a couple items to check back on next time. Most wear metals look good in relation to averages, based on a slightly shorter ~7,700-mile oil run. Nickel is slightly elevated, but all on its own that's not usually any big deal, so we'll just watch how it trends. Sodium also turned up, and since it's not a common diesel oil additive, it may show a little coolant in the oil - but not much at all. If the coolant level is steady, that'll just be an item to monitor, too. 1.5% fuel isn't cautionary, and the TBN was fine at 2.6. Check back for trends.

[catskillclimber]

If there was a straight leak of coolant into the oil then potassium values should be higher too. If they are in single digits I'd lean heavily toward the EGR cooler leaking.

[capt_slow]

Coolant level: 46821 on the odo, cold engine


It's been a little over 5K since the last check and the coolant bottle is pretty much back to where it was before. Topped up about 1 Cup of coolant to bring it back to the seam.

[shkreli65]

New to the forum. My car was doing the same thing every 5000-7000 miles I would have to add about 1/2 quart to 1 quart coolant. I had the recall done and they ndf the vechile. About 2 mouth ago the cooler failed and holes in the intake. If you don't know where the coolant is going there's probably a small leak in the cooler when the car gets hot.

[capt_slow]

Finally brought the F31 to the dealer to have them look at the dropping coolant issue. To my surprise, there is a open safety recall for the EGR Cooler, this is a new one as it shows up on the dealer system but not the online BMW recall database.

My car passed inspection on the first EGR Cooler recall (18V-755), but it seems like the car is now getting a redesigned part. Parts are still not available yet, but nice to know I might be getting my slow coolant drop problem fixed.

https://www.consumerreports.org/car-...k-a7622678572/

[Enabled]

Originally Posted by capt_slow

Finally brought the F31 to the dealer to have them look at the dropping coolant issue. To my surprise, there is a open safety recall for the EGR Cooler, this is a new one as it shows up on the dealer system but not the online BMW recall database.

My car passed inspection on the first EGR Cooler recall (18V-755), but it seems like the car is now getting a redesigned part. Parts are still not available yet, but nice to know I might be getting my slow coolant drop problem fixed.

https://www.consumerreports.org/car-...k-a7622678572/

My dad's X3 28d had originally passed the first recall, as it was low mileage, and then developed the leak later. We were refilling the coolant every 1-2 months. I had a bit of a fight with the BMW dealer, but they eventually re-did the check, and found it leaking. The dealer replaced the EGR cooler and intake manifold on the recall. It took 5 weeks because of incompetence and loads of issues, but it was finally done.

[FaRKle!]

Originally Posted by capt_slow

Finally brought the F31 to the dealer to have them look at the dropping coolant issue. To my surprise, there is a open safety recall for the EGR Cooler, this is a new one as it shows up on the dealer system but not the online BMW recall database.

My car passed inspection on the first EGR Cooler recall (18V-755), but it seems like the car is now getting a redesigned part. Parts are still not available yet, but nice to know I might be getting my slow coolant drop problem fixed.

https://www.consumerreports.org/car-...k-a7622678572/

Do you know which part is replaced in the new recall? I also have a slow coolant loss, but I just top it off every oil change.

[capt_slow]

Originally Posted by FaRKle!

Do you know which part is replaced in the new recall? I also have a slow coolant loss, but I just top it off every oil change.

Looks like a new-design EGR cooler and intake manifold (if damaged). No parts are available yet, so I may need to come back at a later time when they arrive.

Dealer did look at the dropping coolant levels. Car passed another pressure test and they diagnosed the leak as coming from the connector in the expansion tank. At this point, I'm getting a new EGR cooler regardless, so I'm ok with this.