[chippychip]

How many of you are having issues with your BMW 340i eating coolant? I'm up to 2000 miles and have already added half a gallon between the engine coolant and intercooler tank. By the way, I've read too many posts where people think the second coolant tank is for the turbo when it's really for the air to water intercooler.

[F30MGM]

lost a little bit, topped off with distilled water and havent had a issue yet

[ErkanTR16]

Almost 20K miles and haven't noticed any leaks. However, 2nd week of my purchase back in February iDrive system showed a low coolant warning. Took it to service center and the second coolant tank was empty. Service center stated maybe they forgot to fill it at production plant.

[goj]

I had the coolant light come on at 7700 miles. Everything seemed fine they topped off the coolant and I checked today and it is still above the minimum requirement

[goj]

Originally Posted by Erkan_340i

Almost 20K miles and haven't noticed any leaks. However, 2nd week of my purchase back in February iDrive system showed a low coolant warning. Took it to service center and the second coolant tank was empty. Service center stated maybe they forgot to fill it at production plant.

This is most likely what is happening with early production B58s like ours

[insanecoder]

Mine looked low in fact lower than minimum
so I filled it to max
and surprisingly it exceeded that level so Im not sure where or how but some of the coolant came back from the dead and now Im over max

[ErkanTR16]

Originally Posted by goj

This is most likely what is happening with early production B58s like ours

I agree.

[CruzM3]

Normal for the B58 to experience this after delivery. Just top off and keep an eye on it. It shouldn't lose any more coolant again. If so have it checked out at the dealer. This was told to me by dealer.

[cer6526]

Light came on around 14K miles after the first cold day of the year, took it to the dealer and got it topped off. Oil temps were fine before then. Everything's been good since.

[hollandog]

yes 7500 miles and topped up twice already.

[three40_6ix]

Haven't had any coolant issues yet and I have about 9800 miles on my car so far. But I guess it is something to look out for!

[str86diesel]

I just took my 340 into the shop for this, as it kept saying "low coolant." The dealer stated that they have reported several cases to bmw and their response has been that since they use a 50/50 mix and the B58 burns hotter, there is faster evaporation of the water, which then makes the coolant low. Mixed with the fact that the sensors are way to sensitive.

They topped of my fluid and no more low coolant light

[goj]

Originally Posted by _josh.340i

Haven't had any coolant issues yet and I have about 9800 miles on my car so far. But I guess it is something to look out for!

I would check both tanks after being parked over night. The eyeball check is easy.

[goj]

Originally Posted by str86diesel

I just took my 340 into the shop for this, as it kept saying "low coolant." The dealer stated that they have reported several cases to bmw and their response has been that since they use a 50/50 mix and the B58 burns hotter, there is faster evaporation of the water, which then makes the coolant low. Mixed with the fact that the sensors are way to sensitive.

They topped of my fluid and no more low coolant light

So you're saying that once the mixture was closer to 100% coolant you're good?

[cmplaya]

light came on around 15K miles, then topped off with 8 ounces distilled water no problems 2 months later

[str86diesel]

Originally Posted by goj

So you're saying that once the mixture was closer to 100% coolant you're good?

According to the dealer, once the mixture was closer to 100%, that meant that the water has evaporated, thus leaving the system "low" on coolant. Whether its true or not is still yet to be determined, just repeating the dealers speech.

[TheObviousChild]

I got the "Low Coolant" alert at about 6500 miles. Picked up a gallon of BMW Blue to keep in my garage going forward.

[rambalu80]

In the first 6 months, my coolant bottle cap came loose and I lost about a half gallon of coolant. A month later, my coolant pump failed and lost pretty much all coolant. So, yes, in these ways, I was forced to add more coolant.

No other coolant loss that I know of though.

[NISFAN]

Originally Posted by str86diesel

I just took my 340 into the shop for this, as it kept saying "low coolant." The dealer stated that they have reported several cases to bmw and their response has been that since they use a 50/50 mix and the B58 burns hotter, there is faster evaporation of the water, which then makes the coolant low. Mixed with the fact that the sensors are way to sensitive.

They topped of my fluid and no more low coolant light

A clear example of a non technical person trying to come up with a technical explanation. And failing miserably if I might add.

The B58 cooling system is of a pressurised design and is therefore a sealed system. It will not allow vapour to escape, unless the pressure becomes so high it overcomes the pressure relief device. This happening in normal operation would not be considered acceptable.

More likely is there is an underlying issue affecting the cooling circuit. This could be porosity in the castings, weeping gaskets, leaking cooled devices (turbo, egr, oil cooler, etc) and so on.

[rak299]

I think the last answer is not right. Pressure builds up quickly in the sealed cooling system as the temperature rises after the temperature exceeds the boiling point of the same mixture in an unpressurized container. Under normal operation, the radiator and fan cool the mixture to keep the temperature below a temperature that would allow vapor to escape via the pressure relief valve. I don't know the exact temperatures for this engine, but thermostats stay closed until the coolant temperature reaches a normal operating temperature of about 88C. I seem to remember that relief valves normally vent at 1 bar over ambient temperature. For a cooling system with only water, that would be about 115C (15C over the normal boiling point). So, in normal operation a water-coolant car would operate at temperatures between 88C and 115C. On a liquid with a higher boiling point (like coolant) the pressure would start building at a higher point. I don't know about BMW antifreeze, but Ethyl Glycol has a boiling point of nearly 200C. A water-antifreeze mixture would have a boiling point between those numbers. If you graphed temperature vs. antifreeze concentration, it would be a straight line. More coolant and less water would give a higher boiling point and less likely to vent. An Ethyl Glycol-only coolant mixture could operate without venting between 88C and about 215C.

[NISFAN]

Originally Posted by rak299

I think the last answer is not right. Pressure builds up quickly in the sealed cooling system as the temperature rises after the temperature exceeds the boiling point of the same mixture in an unpressurized container. Under normal operation, the radiator and fan cool the mixture to keep the temperature below a temperature that would allow vapor to escape via the pressure relief valve. I don't know the exact temperatures for this engine, but thermostats stay closed until the coolant temperature reaches a normal operating temperature of about 88C. I seem to remember that relief valves normally vent at 1 bar over ambient temperature. For a cooling system with only water, that would be about 115C (15C over the normal boiling point). So, in normal operation a water-coolant car would operate at temperatures between 88C and 115C. On a liquid with a higher boiling point (like coolant) the pressure would start building at a higher point. I don't know about BMW antifreeze, but Ethyl Glycol has a boiling point of nearly 200C. A water-antifreeze mixture would have a boiling point between those numbers. If you graphed temperature vs. antifreeze concentration, it would be a straight line. More coolant and less water would give a higher boiling point and less likely to vent. An Ethyl Glycol-only coolant mixture could operate without venting between 88C and about 215C.

Aren't you backing up what I said?

We agree that in normal operation, the venting of a pressurised system should not happen. It would also take a pretty large increase in 'normal' engine running temperature for "the B58 runs a little hotter" comment to force a 'same design spec' system to start venting (due to excess pressure).

This fluid loss is more down to one of the mechanical factors I mentioned above than a new venting phenomenon brought about by the B58 cooling characteristics, IMO of course.

[rak299]

You may be right, but I don't know what concentration got installed at the factory. I will pretend that BMW coolant has a boiling point of 180C and water boils at 100C. If we assume the correct liquid is a 75/25 mixture (25% water), it would boil at 160C without a cap installed and vent at about 175C with the pressure cap. If some cars got produced with 50% water, it would lower the temperatures to 140C without a cap and vent at 155C with a cap. Normal coolant temperature under load might be 160C. In that case, it would vent (evaporate) with the wrong mixture and not vent when the concentration is raised. I know that coolant is normally heated above the normal boiling point because I know someone (not very bright) who got badly burned trying to remove a cap before the engine cooled down.