Strange Coolant Loss...

RayLivingston · 03-11-2019, 10:52 AM

My '07 335i has a strange coolant loss. It'll go several weeks without losing a drop, then suddenly be down about a pint or so - just enough for the light to turn on. Given that it is NOT a constant leak, I'm not sure a pressure test will accomplish much. Any suggestions where to look? Unfortunately, it is the rainy season here at the moment, so visually checking for leaks is pointless - EVERYTHING is wet underneath all the time.

Regards,
Ray L.

dyrus587 · 03-11-2019, 12:27 PM

Quote:

Originally Posted by RayLivingston

My '07 335i has a strange coolant loss. It'll go several weeks without losing a drop, then suddenly be down about a pint or so - just enough for the light to turn on. Given that it is NOT a constant leak, I'm not sure a pressure test will accomplish much. Any suggestions where to look? Unfortunately, it is the rainy season here at the moment, so visually checking for leaks is pointless - EVERYTHING is wet underneath all the time.

Regards,
Ray L.

i also have a similar problem, same year and model

coolant is almost evaporating in my car since i have to refill it every week or so

very minimal leak drops underneath

any ideas??

SilverSlug · 03-11-2019, 01:26 PM

Have you tried smelling the exhaust? Does it smell like coolant?

Any coolant coming out of the exhaust?

Does your oil cap have milkshake looking residue underneath?

Coolant loss may be associated with a head gasket leak.

Also, could be a hairline fracture somewhere that only drains coolant once it gets hot enough to expand.

Does your coolant disappear more after a long drive or spirited driving?

RayLivingston · 03-11-2019, 07:33 PM

I've seen no pattern to the loss. As I said, it will go for weeks without losing a single drop, then suddenly it will be down a pint or more. The system DOES hold pressure. I drove the car yesterday, then parked it overnight. When I opened the carp this morning to check the level, there was still pressure, as I heard the slight hiss as I unscrewed the cap.

NO indications of problems - the coolant is as clean as the day I put it in, about 6 months ago.

Looks like we've got 7-8 days of dry weather coming, so I can pressure-wash the engine bay, then look for signs of leakage.

Regards,
Ray L.

Emilime75 · 03-11-2019, 08:07 PM

Quote:

Originally Posted by dyrus587

coolant is almost evaporating...Very minimal leak drops underneath

dyrus587 · 03-11-2019, 08:11 PM

Quote:

Originally Posted by Emilime75

Quote:

Originally Posted by dyrus587

coolant is almost evaporating...Very minimal leak drops underneath

i am aware of the leaks but it doesn't add up that 1 or 2 drops will require me to fill up coolant again after 1 week

SilverSlug · 03-16-2019, 01:16 AM

Fill up the coolant to normal levels, then go for a long drive, including some spirited driving.

If there is a hairline crack in the block somewhere, it will still hold pressure once the engine cools down. Furthermore, it may not leak through there if the engine does not get hot enough to expand.

Have you smelled the oil cap, as well as the exhaust?

If it’s not leaking, it is most likely being consumed by the engine. The only way that would happen is if it is mixing into the oil or through a gasket.

03-11-2019, 10:52 AM	#1
RayLivingston Lieutenant 140 Rep 445 Posts Drives: '07 335i Sedan Join Date: Aug 2018 Location: California iTrader: (0)	Strange Coolant Loss... My '07 335i has a strange coolant loss. It'll go several weeks without losing a drop, then suddenly be down about a pint or so - just enough for the light to turn on. Given that it is NOT a constant leak, I'm not sure a pressure test will accomplish much. Any suggestions where to look? Unfortunately, it is the rainy season here at the moment, so visually checking for leaks is pointless - EVERYTHING is wet underneath all the time. Regards, Ray L.
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03-11-2019, 01:26 PM	#3
SilverSlug Hey, where have you been all my life? 680 Rep 1,401 Posts Drives: 2011 M3 6MT Join Date: Jul 2018 Location: San Francisco, CA iTrader: (2)	Have you tried smelling the exhaust? Does it smell like coolant? Any coolant coming out of the exhaust? Does your oil cap have milkshake looking residue underneath? Coolant loss may be associated with a head gasket leak. Also, could be a hairline fracture somewhere that only drains coolant once it gets hot enough to expand. Does your coolant disappear more after a long drive or spirited driving?
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03-11-2019, 07:33 PM	#4
RayLivingston Lieutenant 140 Rep 445 Posts Drives: '07 335i Sedan Join Date: Aug 2018 Location: California iTrader: (0)	I've seen no pattern to the loss. As I said, it will go for weeks without losing a single drop, then suddenly it will be down a pint or more. The system DOES hold pressure. I drove the car yesterday, then parked it overnight. When I opened the carp this morning to check the level, there was still pressure, as I heard the slight hiss as I unscrewed the cap. NO indications of problems - the coolant is as clean as the day I put it in, about 6 months ago. Looks like we've got 7-8 days of dry weather coming, so I can pressure-wash the engine bay, then look for signs of leakage. Regards, Ray L.
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03-16-2019, 01:16 AM	#7
SilverSlug Hey, where have you been all my life? 680 Rep 1,401 Posts Drives: 2011 M3 6MT Join Date: Jul 2018 Location: San Francisco, CA iTrader: (2)	Fill up the coolant to normal levels, then go for a long drive, including some spirited driving. If there is a hairline crack in the block somewhere, it will still hold pressure once the engine cools down. Furthermore, it may not leak through there if the engine does not get hot enough to expand. Have you smelled the oil cap, as well as the exhaust? If it’s not leaking, it is most likely being consumed by the engine. The only way that would happen is if it is mixing into the oil or through a gasket.
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