[Elvisfan]

Well,looks like I have to bring my car in. I’m losing coolant. No obvious leak. And no drips. I do a 40 mile round trip and coolant goes from between min and max to just below min. Any thoughts?
I had the low coolant message. Since than I have had to put coolant in twice. Not much,but some.
Thanks.

[eluded]

Barometric pressure variation?

[Billfitz]

If there's no evidence of a leak then it could be going out the exhaust. A bad head gasket is one way that can happen.

[IraHayes]

Do you have any white smoke (steam) coming out of your exhaust? If you do, that would be indicative of a head gasket leak as Bill suggested. If it's a fairly small leak, you may not see any smoke/steam. If that's the case, there the "smell test." Smell the exhaust and see if it has a "sweet" smell to it. Just don't take any deep breaths lol. They also sell kits on Amazon that you can use to test for a failed head gasket, and they actually work really well. Not sure, but they may sell them at local auto part stores as well.

https://www.amazon.com/dp/B000NPDL76...v_ov_lig_dp_it

[Wgosma]

You can borrow a "block tester" at most decent auto parts stores; you pay 8 bucks to buy the fluid. I've used these simple devices, quick and easy to do- generally considered gold standard when evaluating potentially head gasket failure.

Good luck/Bill

[IraHayes]

Originally Posted by Wgosma

You can borrow a "block tester" at most decent auto parts stores; you pay 8 bucks to buy the fluid. I've used these simple devices, quick and easy to do- generally considered gold standard when evaluating potentially head gasket failure.

Good luck/Bill

Same exact kit I have in my toolbox. And I agree on it being the gold standard.

[Elvisfan]

It’s under warranty. Going in next Friday. Hopefully,they’ll figure it out. Thanks all.

[simonelwell]

I had a coolant loss on my old 335i - dealer tested for a leak and said there was no leak. So they concluded I needed a thermostat - which was hard to do. £500+ later having replaced the thermostat I still had the problem - which led to further investigation and they found the leak.

Conclusion: If looks like a duck and waddles like a duck...

[Elvisfan]

Originally Posted by simonelwell

I had a coolant loss on my old 335i - dealer tested for a leak and said there was no leak. So they concluded I needed a thermostat - which was hard to do. £500+ later having replaced the thermostat I still had the problem - which led to further investigation and they found the leak.

Conclusion: If looks like a duck and waddles like a duck...

It’s a leak.

[Billfitz]

Could be a goose. It's the quack that confirms the theory.

[Elvisfan]

My car is spending the night at the dealer to do a pressure test. No obvious signs that they could see.

[RedScytheM3]

Originally Posted by billfitz

could be a goose. It's the quack that confirms the theory.

🙌🏽

[Elvisfan]

It sounds like they pulled everything apart. Couldn’t find a leak anywhere. Blamed it on dissipation.
Cause: air pocket and dissipation of coolant
Correction: performed several pressure test to both high temp and low temp cooling systems. although there was some pressure loss over 4 hours the coolant level measured never dropped in the expansion tanks. removed oil lines from transmission to see if leak occurred inside cooler, that was ok. removed under body panels and inspect for head gasket leak, that was ok.removed throttle and inspect intake cooler, that was ok. closely inspected radiator and heat exchanger they were ok.. vehicle is experiencing eiter a air pocket which i did bleed the system to be sure it was free of air and dissipation which is normal for a vehicle to lose some coolant due to water/coolant mixture. sometimes the water evaporates causing the level to drop.