Coolant light came on...

[CERF04ZHP]

I was just pulling out of the touch free wash on Saturday, and through those high speed driers, and my coolant light tripped on. So I pulled over to the side, shut the engine off, and checked the level and everything was fine. Couldn't really see if there were any leaks because the undercarriage was still wet. Got in and started the engine, no light on. Drove 10 miles home, check fluid level again (ok) and check out underneath, bone dry.
Suggestions?

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[danewilson77]

Keep an eye on it.

HTC Thunderbolt+TT

[llll1l1ll]

The sensor could be faulty. Best bet is to check it every couple of days. Once a week is best.

Also, be careful checking coolant on a hot engine!

[midlandtech]

I agree if the light is coming on I would check it daily for a week or 2... if the fluid level never changes I would start thinking sensor

[Washburn]

Sudden drops in outside temp can trigger the light even if the levels are ok.

or even sudden spikes: High heat drier --> plastic expands --> (tank bigger) --> level drops a bit --> light?

[CERF04ZHP]

Got it. Thanks fellas.

[CERF04ZHP]

Okay... now after a couple weeks of analysis, here's what's going on: I start the car in the morning, light pops on after driving for about 5 minutes, stays on for a minute or two, then shuts off... I cruise 40 miles down the highway @ 80mph, get off at the exit for work (or home), and as soon as I get back down to stop and go traffic, light pops back on for a minute or so, then shuts back off. Very strange. Does it every day now. Level is fine.
? ? ?

[danewilson77]

I bet you have a small crack in your expansion tank. These indications are nearly identical to mine. I believe the crack would swell, due to temp....or pressure in the tank......then close back up. Super slow leak.....never noticed any "leak" per se', then finally found it when I pre-emptively changed out the tank.

Have you completed a really good inspection of all the problem area's?

http://i1015.photobucket.com/albums/af278/nicee46/Maintenance%20and%20Misc/DSC02730sz1200.jpg

[nike001]

I bet you had your heat on..

Amirite?

[LivesNearCostco]

What does your ET float (level indicator) look like when the engine is completely cold?

[CERF04ZHP]

Dane - dammit, I think you're right again... I can see a little bit of liquid on the belly pan when I look straight down past the expansion tank.
Nike - The whole time.
Costco - When I take the cap off the exp. tank, the float pops right up to the top, whether the engine is cold or @ operating temperature. The fluid is rather "frothy" though - not normal? I just turned 130k this week... I think it's time for cooling system overhaul #2 before whatever's going on leaves me on the side of the highway with a pegged temp. gauge....

[Nivo]

Mine came on and once I took a peek i had a bad expansion tank.

[LivesNearCostco]

Ok I'm only hazarding a guess, but that guess is you were either overfilled on coolant or have an air pocket trapped in there. That way you can lose a little coolant but still have the float pop to the top every time, cold or warm. But that doesn't explain why your low coolant light came on. Hmmmm... probably what the other said, that your ET has a very small crack.

Or need to re-bleed the cooling system?



Costco - When I take the cap off the exp. tank, the float pops right up to the top, whether the engine is cold or @ operating temperature. The fluid is rather "frothy" though - not normal? I just turned 130k this week... I think it's time for cooling system overhaul #2 before whatever's going on leaves me on the side of the highway with a pegged temp. gauge....

[nike001]

OP, Don't jump to conclusions of needing a whole new cooling system. People here and on every other BMW forum are so quick to jump to that because of how many problems they cause.

Take the cap off and fill it up. The fluid will probably fill to the top but then will drop down. Don't just fill it up quick and pop on the cap and go. Wait for the fluid to go from the top of the fill cap to the rest of the expansion tank. Then continue to fill again.

What probably tripped your light was that your coolant was on the verge of being low. The coolant goes in to your heater core for your heat, and the amount of coolant that goes in to the core was probably just enough to trip your light. If you turned your heat off, you probably would have noticed that your low coolant light disappeared after about 20-30 seconds.

[danewilson77]

^Great advice above. Fill... Super slow. When you think you're Going too slow, go slower.

I put 2 gallons in my system, and never had to bleed. Done.

HTC Thunderbolt+TT

[CERF04ZHP]

Okay now that I definitely know I need an expansion tank... which one do I get?

For example: http://www.ecstuning.com/BMW-E46-330i-M54_3.0L/Engine/Cooling/Expansion_Tank/

Not to say I would definitely get it from ECS, but is it worth getting an "aftermarket" as opposed to OE?

[nike001]

Up to you if you wanna get OEM or not. I know I'd personally go BMW, since I like to keep everything OEM on my car..

[gr330zhp]

I went with aftermarket only on my expansion tank when I did my overhaul, and goes what's the only thing that has failed :facepalm Noticed today, I think it may be leaking slightly

Going to throw on my old OE tank until I buy a new OE tank. Go OE Channing

[CERF04ZHP]

Good call on the OE fellas.

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[kayger12]

Yeah, definitely OE for cooling parts. Seem to be a lot of premature failures (and by premature, I mean even more premature than the OE premature failures :facepalm) with after market expansion tanks and hoses lately.

[328ioc]

I was just pulling out of the touch free wash on Saturday, and through those high speed driers, and my coolant light tripped on. So I pulled over to the side, shut the engine off, and checked the level and everything was fine. Couldn't really see if there were any leaks because the undercarriage was still wet. Got in and started the engine, no light on. Drove 10 miles home, check fluid level again (ok) and check out underneath, bone dry.
Suggestions?


HTC EVO / Tapatalk

On suggestion I would like to add since I just did my thermostat this weekend is make sure you check the level when the engine is COLD.

Since the coolant expands checking the level while the engine is hot will always give a false positive. unless you are 100% empty of course.