[StannisBaratheon]

2016 340i xDrive - 44k miles

My coolant light hasn't come on but looking under the hood yesterday I saw dried coolant residue that must have sprayed out of the cap. It's been hot in the northeast so I'm wondering if moderate/hard driving plus the outside temperature is too much for the cooling system, causing it to burp out of the cap? I cleaned up the area around the cap and I'm going to keep an eye on it. A friend of mine said his mini did the same thing when it got very hot out.

[kern417]

Originally Posted by kern417

I have service scheduled for next Friday so I checked my levels and the engine coolant tank is dry again. 2 years old and just hit 10k miles. Going to add that to the service for them to pressure test and replace the cap if the test passes. I can see coolant on the threads and it's hard to remove, so I'm leaning towards the cap being the issue.

Dropped it off and, as suspected, dealer says no problem found. They inspected for leaks and did a pressure test, then topped up the reservoir. I asked if they tested the cap and they claim attaching the pressure tester to the reservoir makes sure that the coolant isn't seeping past the threads, but that doesn't take the cap out of the picture.

They also said that they won't dig deeper unless the coolant drops to min within 30 days. So me saying that it was topped off last year is "not a big deal" even though my car has only 10,000 miles.

I'm planning on renting a leakdown tester and checking for headgasket damage myself, since they won't. If that isn't it, i'll get a new cap for the reservoir.

[jbb2388]

Just had my low coolant warning message come on at 40K the other day. Wasn't terribly low. Added maybe 8oz to the main tank. Secondary tank was full.

[BMWILUVU]

Low coolant message came on today. The main reservoir was completely dry to sight. The secondary reservoir was at maximum.

[cfm56d7b]

Originally Posted by BMWILUVU

Low coolant message came on today. The main reservoir was completely dry to sight. The secondary reservoir was at maximum.

How many miles does the car have? When was coolant verified to be full?

My vehicle was at the dealer for a low coolant warning. I added exactly 1 liter of 50/50 concentrate / distilled water mixture prior to driving to the dealer.

The dealer determined the root cause to be a defective reservoir cap.

When the car is hold, remove the main tank reservoir cap and look for white residue under the cap.

[BMWILUVU]

Originally Posted by cfm56d7b

How many miles does the car have? When was coolant verified to be full?

My vehicle was at the dealer for a low coolant warning. I added exactly 1 liter of 50/50 concentrate / distilled water mixture prior to driving to the dealer.

The dealer determined the root cause to be a defective reservoir cap.

When the car is hold, remove the main tank reservoir cap and look for white residue under the cap.

I am a few thousand miles to the end of warranty. There is residue but I cannot believe a full tank of coolant is evaporated through the cap. Does anyone have access to TSBs concerning loss of coolant?

[cfm56d7b]

Originally Posted by BMWILUVU

I am a few thousand miles to the end of warranty. There is residue but I cannot believe a full tank of coolant is evaporated through the cap. Does anyone have access to TSBs concerning loss of coolant?

The defective reservoir cap on the main tank has been reported by other forum members. I don't know if a TSB exists specifically describing this problem.

[kern417]

Originally Posted by BMWILUVU

I am a few thousand miles to the end of warranty. There is residue but I cannot believe a full tank of coolant is evaporated through the cap. Does anyone have access to TSBs concerning loss of coolant?

Originally Posted by cfm56d7b

The defective reservoir cap on the main tank has been reported by other forum members. I don't know if a TSB exists specifically describing this problem.

Sorry to keep ranting (I feel like I keep responding to the same people in all these threads), but a TSB won't be issued unless it's a common issue that takes a long time to repair. Then they'll send a TSB to dealers to speed up diagnosis.

At least on my car, they only pressure tested the system. When I asked if they pressure tested the cap, they claimed that the pressure test simulates a cap test as well because pressure would still leak past the threads.

Well what if the cap isn't to the same tolerances as your machined adapter? So that makes me think they don't even have an appropriate adapter/test kit to check if the cap is good.

[azuritschwarz]

My F32 has had low coolant twice now in the 40,000 kilometres I have owned it (since new). Never once gave me a low coolant light but I check the levels every week or so; the large tank has been well below the minimum both times, while the smaller tank has remained relatively constant between minimum & maximum.

I have also had my system pressure tested twice, both times leaving with a good bill of health.

When the lid for the large tank is removed, there are a lot of white flakes around the threads.

Coolant has been topped again, & I will be going to the dealer this week. I will update once I *hopefully* get a new coolant cap.

[BMWILUVU]

Originally Posted by kern417

Sorry to keep ranting (I feel like I keep responding to the same people in all these threads), but a TSB won't be issued unless it's a common issue that takes a long time to repair. Then they'll send a TSB to dealers to speed up diagnosis.

At least on my car, they only pressure tested the system. When I asked if they pressure tested the cap, they claimed that the pressure test simulates a cap test as well because pressure would still leak past the threads.

Well what if the cap isn't to the same tolerances as your machined adapter? So that makes me think they don't even have an appropriate adapter/test kit to check if the cap is good.

Just had my expansion tank replaced. Fingers are crossed.

[Kaisah]

Just to add my experience to this. 2017 340i B58, 31k miles, was checking error codes with Bimmerlink and found one stored regarding low coolant. No iDrive errors/warnings though.

Looking in main/large tank and its well below the minimum (not totally dry though). Buying some coolant today and will top up. Am I supposed to mix this 50/50 with de-ionised water or is it ok to top up slightly with pure coolant?

I have only owned the car for 2 weeks and done maybe 500 miles in it, so not sure what it’s been like on coolant up until now.

The car is/was an AUC however direct from BMW.. so disappointing they haven’t checked the coolant..

[kern417]

Originally Posted by Kaisah

Just to add my experience to this. 2017 340i B58, 31k miles, was checking error codes with Bimmerlink and found one stored regarding low coolant. No iDrive errors/warnings though.

Looking in main/large tank and its well below the minimum (not totally dry though). Buying some coolant today and will top up. Am I supposed to mix this 50/50 with de-ionised water or is it ok to top up slightly with pure coolant?

I have only owned the car for 2 weeks and done maybe 500 miles in it, so not sure what it’s been like on coolant up until now.

The car is/was an AUC however direct from BMW.. so disappointing they haven’t checked the coolant..

IF it's not much then it's safe to top up with just distilled water or just coolant. But the best method is to top of with 50/50. What I do is buy 2 gallons of distilled water, pour one out, split the difference between both jugs so they're half full, then top up both jugs with the BMW coolant. Now you have 2 gallons of 50/50 on standby for anytime you need it in the future.

I sent an email to the service manager at my local dealer to give him one more chance to make it right. If I have to buy a replacement cap myself, then I'm never going back. What's the point in maintaining a warranty if you have to fight for a $20 repair?

[Buzzo]

Coolant reservoir cap was replaced at 30K. Now at about 46K and back to refilling the main reservoir with residue showing on the cap treads. Will bring it in for its last service under warranty in a couple of weeks.

[kern417]

Originally Posted by Buzzo

Coolant reservoir cap was replaced at 30K. Now at about 46K and back to refilling the main reservoir with residue showing on the cap treads. Will bring it in for its last service under warranty in a couple of weeks.

Only other option is to replace the reservoir is the cap is good. Otherwise both are just too loose by design and it's allowing coolant to evaporate past. That would be pretty disappointing on an engine design that's so dependent on coolant.

[d0ugmac1]

2018 340ix 6MT MPPSK (B58)- just got the iDrive warning about coolant, car has 12.5kmi..this happened just as a below freezing cold snap blew through (common weather situation for first reports).

Main tank was almost empty...well below the MIN mark, intercooler tank was just below MAX. Took about 700ml to bring main tank back up. Cap was hard to remove initially with same thread/powder issues reported earlier in this thread. Since first removal and rinse, has been very easy to spin on/off.

Dealer offered free top off...but wasn't driving car due to draconian warning. Bought coolant and topped off with 50/50 mix at home. Have had to top up slightly after each drive cycle since...but this could be a slow air bleed issue. Monitoring and will report back to thread.

Of note, there were a couple of non-warning drive cycles before the message returned a second time.

[antzcrashing]

Had to add 1 time, 440i 18k miles of ownership

[cfm56d7b]

2017 440i GC with 26K miles. Low coolant wanting at 25.5K miles. Main tank reservoir cap replaced under warranty. So far so good.

[BMW11]

Received the low coolant warning for the first time. Checked both Reservoirs. Both were just below min on a cold morning. I can not believe and didn't expect how hard it was to turn the Large Cap to take off and to put back on. It was really hard to put back on to get the arrows aligned. After I re-started the car the warning went away. Going to BMW to get levels topped off.

[kern417]

Update - My dealer's service manager decided to give me a replacement cap to see if it fixes the issue. Waiting for it to come in (on order) and I'll replace it myself. I'm tempted to buy a reservoir and pressure test the combination. Something clearly isn't sealing the system.

[mujjuman]

Originally Posted by kern417

Update - My dealer's service manager decided to give me a replacement cap to see if it fixes the issue. Waiting for it to come in (on order) and I'll replace it myself. I'm tempted to buy a reservoir and pressure test the combination. Something clearly isn't sealing the system.

2015 build year 340 here too, 2016 model. Same issue with coolant consumption...

Topped off at dealer 3 times, passed pressure tests, no evidence of leaking.
I topped off twice myself. Both tanks were bone dry a couple of times, other times it was just the main tank.

Dealer did not think to replace the cap... let me know how it goes. I will probably end up buying caps on my own for both tanks and replace them myself.

I'm about to go outside right now and check my coolant level again after not starting the car for 24 hours, hoping for the best.


[EDIT]
Secondary tank was just above Max, so it stayed the same.
Main tank was just at Max. I think it did go down a bit because I had it just above Max when I last topped it off. Will keep an eye on it and update later.

[Pray for Mojo]

Our 2018 March built X3 M40i just had it's first low coolant warning. 20k km/12k miles. My 2014 M235i's N55 has never needed coolant in 90k km.

This isn't normal and I don't think people should be letting the warranty period expire without making a stink. There must be a common flaw since this across a few years and numerous models.

[dime4dice]

Took the car in today to check why I’m loosing soo much coolant. Turns out I have to replace my water pump, there’s a leak coming out.