2011 e90 Sedan Coolant Leak

Aprater17 · 02-08-2024, 10:21 AM

So I have been battling a coolant leak for quite some time now and I am truly stumped. About a year and a half ago I would get a "low coolant level" message every once in a while and when I would check, it wasn't just low but actually just empty. We replaced the reservoir tank soon after this began happening which helped for a short amount of time before it started happening again. This past July, we decided to replace the water pump, thermostat, and almost every hose line in the coolant system. This also helped for a short while and I am now losing coolant again. Occasionally when I get in I will get the error and check the level but it is still completely full, while other times it will be completely empty. I have noticed some dried residue on the reservoir tank itself recently but with no obvious signs of where it could be coming out of. I believe that pressure is somehow building up within the system but I have no clue how it would be as I always make sure to bleed the lines and keep the reservoir cap on firmly. I have officially run out of ideas and am getting very tired of buying coolant and refilling it once a week. Any assistance is very much appreciated.

oVeRdOsE. · 02-08-2024, 10:29 AM

All the component are prone to leak on those cars.

- Did you see drip on the floor ? Main issue : radiator, pump/thermostat, all hoses including the expansion return, and turbo line if you have a 335.

- any white smoke out of the exhaust ? You can do the chemical test to see if you have exhaust leak in the coolant system. Inexpensive on amazon.

- Oil is not milky ? If yes, can be the OFHG

in 65k miles, my cooling system hose has been changed twice, radiator twice, expansion once, pump once.

watchout-everyone · 02-08-2024, 11:09 AM

Did you confirm you have no coolant leaks by taking out the floor cover?

Since you mentioned you got the "low coolant" once in a while, i am guessing the leak was slow and/or little at a time. So, those leaked water will just stay on top of this floor cover then evaporate due to hot engine above it or just time.

Might guess is one of the hoses is not secured which was the case for me.

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02-08-2024, 10:21 AM	#1
Aprater17 Registered 0 Rep 1 Posts Drives: BMW e90 Join Date: Feb 2024 Location: Illinois iTrader: (0)	2011 e90 Sedan Coolant Leak So I have been battling a coolant leak for quite some time now and I am truly stumped. About a year and a half ago I would get a "low coolant level" message every once in a while and when I would check, it wasn't just low but actually just empty. We replaced the reservoir tank soon after this began happening which helped for a short amount of time before it started happening again. This past July, we decided to replace the water pump, thermostat, and almost every hose line in the coolant system. This also helped for a short while and I am now losing coolant again. Occasionally when I get in I will get the error and check the level but it is still completely full, while other times it will be completely empty. I have noticed some dried residue on the reservoir tank itself recently but with no obvious signs of where it could be coming out of. I believe that pressure is somehow building up within the system but I have no clue how it would be as I always make sure to bleed the lines and keep the reservoir cap on firmly. I have officially run out of ideas and am getting very tired of buying coolant and refilling it once a week. Any assistance is very much appreciated.
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02-08-2024, 10:29 AM	#2
oVeRdOsE. Lieutenant Colonel 2709 Rep 1,538 Posts Drives: F25 E91 Audi Avnt E90 Cayenne Join Date: May 2018 Location: mtl iTrader: (0)	All the component are prone to leak on those cars. - Did you see drip on the floor ? Main issue : radiator, pump/thermostat, all hoses including the expansion return, and turbo line if you have a 335. - any white smoke out of the exhaust ? You can do the chemical test to see if you have exhaust leak in the coolant system. Inexpensive on amazon. - Oil is not milky ? If yes, can be the OFHG in 65k miles, my cooling system hose has been changed twice, radiator twice, expansion once, pump once.
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02-08-2024, 11:09 AM	#3
watchout-everyone Private First Class 86 Rep 152 Posts Drives: 2011 BMW 328i Join Date: Apr 2023 Location: USA iTrader: (0) Garage List 2011 [0.00]	Did you confirm you have no coolant leaks by taking out the floor cover? Since you mentioned you got the "low coolant" once in a while, i am guessing the leak was slow and/or little at a time. So, those leaked water will just stay on top of this floor cover then evaporate due to hot engine above it or just time. Might guess is one of the hoses is not secured which was the case for me. View post on imgur.com
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