[mwh2009]

Low coolant warning. Took it in to top it off. Took a quart! Seems like a lot. Discovered the 2 sort-of-separate reservoirs. Not sure if they're completely separate or not?

The dude at the BMW service said that if you drain the big one, the little one will empty too, which i thought was either strange/wrong - why have two filler caps if they connect somewhere?

[Thus]

I hit the same issue, but at ~8k miles. I filled up the big reservoir with BMW coolant and all was well.

[CruzM3]

It's common on the b58 to need coolant added sometime after purchase.

[RedKloud]

Originally Posted by Thus

I hit the same issue, but at ~8k miles. I filled up the big reservoir with BMW coolant and all was well.

+1. Others have reported this issue too.

[ErkanTR16]

There's a Thread on here about this. I've experienced this around 300 miles.

[cmplaya]

i had this around 15K

[kentgbr]

Got a low coolant warning at 12.5K miles after one year of driving, needed 2-3 cups to re-fill.

[goj]

I had this issue at 7700 miles. I have done numerous visual tests and now it looks like I am below the minimum marker in the tank again. I am at 13.6k mikes.

It looks like coolant is evaporating and drying out right below my coolant cap. I am on a business trip away from my car but when i get home i will snap a picture of it. BMW has done this before: a bad seal on the cap causes slow evaporation. Everyone reporting this seems to have an early production 340i. I'm thinking the batch of caps is bad. It makes no sense for an engine to burn coolant like this.

[Bee Pee]

Originally Posted by mwh2009

Low coolant warning. Took it in to top it off. Took a quart! Seems like a lot. Discovered the 2 sort-of-separate reservoirs. Not sure if they're completely separate or not?

The dude at the BMW service said that if you drain the big one, the little one will empty too, which i thought was either strange/wrong - why have two filler caps if they connect somewhere?

2 reservoirs

Larger one is for engine cooling system.

2nd smaller one is for water to air charge cooler integrated into intake manifold

[kentgbr]

Originally Posted by goj

I had this issue at 7700 miles. I have done numerous visual tests and now it looks like I am below the minimum marker in the tank again. I am at 13.6k mikes.

It looks like coolant is evaporating and drying out right below my coolant cap. I am on a business trip away from my car but when i get home i will snap a picture of it. BMW has done this before: a bad seal on the cap causes slow evaporation. Everyone reporting this seems to have an early production 340i. I'm thinking the batch of caps is bad. It makes no sense for an engine to burn coolant like this.

I think you might be right, also saw signs of coolant evaporation around the cap. My 2011 N55 had a similar problem that was fixed with a replacement part.

[CruzM3]

I don't have an early production 340i. Mines was built in July 2017 and I have the same problem. I would be interested to know if the M140/240 guys have this issue also.

[SingleturboVert]

Originally Posted by Bee Pee

2 reservoirs

Larger one is for engine cooling system.

2nd smaller one is for water to air charge cooler integrated into intake manifold

Good catch. What is the fluid comprised of for the A2W side?

[225]

Same in the UK, mine was built march 16 and needed coolant at 6k miles.

[mwh2009]

Originally Posted by SingleturboVert

Good catch. What is the fluid comprised of for the A2W side?

It's the same coolant - the service guy at BMW topped off both reservoirs from the same jug

[mookie45]

What are reasons why the car is "burning" so much coolant? I really hope there are no overheating issues

[kentgbr]

Originally Posted by mookie45

What are reasons why the car is "burning" so much coolant? I really hope there are no overheating issues

I tracked my car at an all-day HPDE, seven 20min+ sessions. No signs of overheating and the oil temp didn't budge, unlike my previous N54 335I at the same track.

[CruzM3]

Originally Posted by mookie45

What are reasons why the car is "burning" so much coolant? I really hope there are no overheating issues

It's not burning coolant as what I been told by my dealer is that they just fill it up to the max level at the factory but that the system is not really all the way full until after some driving. Same as if you do a coolant flush on a car. After filling it up and driving for bit you usually have to add more coolant.

[mookie45]

Originally Posted by kentgbr

I tracked my car at an all-day HPDE, seven 20min+ sessions. No signs of overheating and the oil temp didn't budge, unlike my previous N54 335I at the same track.

Ok that's good to know.

Originally Posted by Cruz28/40

It's not burning coolant as what I been told by my dealer is that they just fill it up to the max level at the factory but that the system is not really all the way full until after some driving. Same as if you do a coolant flush on a car. After filling it up and driving for bit you usually have to add more coolant.

Hopefully that is the case. If not, possibly it is something as minor as goj stated about the bad seal on the cap.

[goj]

Originally Posted by Cruz28/40

It's not burning coolant as what I been told by my dealer is that they just fill it up to the max level at the factory but that the system is not really all the way full until after some driving. Same as if you do a coolant flush on a car. After filling it up and driving for bit you usually have to add more coolant.

My system was pressure tested and totally fine. No leaks. Therefore coolant is evaporating somehow. And the big cap looks to be the culprit.

[kern417]

that's really not ok imo. if i do a coolant flush, it might take 2-3 thermostat cycles to get it topped off, and that's worst case scenario. 1000s of miles and some people having to do it twice indicates there is an issue, however minute it may be. i would not say that's typical or normal at all.

[pocky]

Happened to my 340i around 8-9k miles. Both tanks were bone dry.

[Lionel_24k]

refilled for a 3rd time at 12k miles