The coolant level drained my battery dead

radicaltronic · 03-31-2022, 02:41 PM

Hi!
This is not an information request, more, information sharing, so that if you ever find yourself in this situation, you will have read about it before.

Yesterday, after work, going back to my car, I was surprised to see that my battery was totally dead. No headlights were on, but even if, I was at the office for max 3 hours. So something drained very it quickly, not the headlights.

When I finally managed to find booster cables (no boost packs were powerful enough), that I started the engine and recharged the battery, I noticed that my water pump was always running, on&off. Exactly like when you do the hack to purge the coolant (heater/gaz 10 seconds).

What drained my battery was the water pump always switching on/off even without the engine running.

The reason ? I had VERY LOW COOLANT LEVEL. Like nearly empty ( my car wasn't overheating though ). It turns out that when you have very low coolant, and air is in the circuit, the pump will run in order to remove the air bubbles automatically. If you don't have any coolant, it runs periodically forever, or until you add coolant.. or that your battery is dead.

Talk about a Rube-Goldberg fail !

Cheers!

tomasp001 · 04-01-2022, 10:53 AM

Surprised that the coolant level warning light didn't come on way before this happened, but thank you for the heads up!

Ha4cnn · 04-04-2022, 04:09 PM

That is good to know. Thanks for the post

03-31-2022, 02:41 PM	#1
radicaltronic Registered 2 Rep 2 Posts Drives: BMW 335 iXDRIVE E90 Join Date: Dec 2020 Location: Quebec City iTrader: (0)	The coolant level drained my battery dead - You read correctly :) Hi! This is not an information request, more, information sharing, so that if you ever find yourself in this situation, you will have read about it before. Yesterday, after work, going back to my car, I was surprised to see that my battery was totally dead. No headlights were on, but even if, I was at the office for max 3 hours. So something drained very it quickly, not the headlights. When I finally managed to find booster cables (no boost packs were powerful enough), that I started the engine and recharged the battery, I noticed that my water pump was always running, on&off. Exactly like when you do the hack to purge the coolant (heater/gaz 10 seconds). What drained my battery was the water pump always switching on/off even without the engine running. The reason ? I had VERY LOW COOLANT LEVEL. Like nearly empty ( my car wasn't overheating though ). It turns out that when you have very low coolant, and air is in the circuit, the pump will run in order to remove the air bubbles automatically. If you don't have any coolant, it runs periodically forever, or until you add coolant.. or that your battery is dead. Talk about a Rube-Goldberg fail ! Cheers!
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04-01-2022, 10:53 AM	#2
tomasp001 Private First Class 14 Rep 106 Posts Drives: 2008 BMW 335i Join Date: Nov 2019 Location: Scarborough, ON, Canada iTrader: (0) Garage List 2008 BMW 335i [0.00]	Surprised that the coolant level warning light didn't come on way before this happened, but thank you for the heads up! __________________ __________________ '08 335i AT Titanium Silver \| MHD Stage 2+ (91 oct) \| xHP Stage 3 \| VRSF FMIC [7.5"] \| BMS CP + Tial BOV \| VRSF Catless DP \| VRSF Exhaust [Street] \| BMS Dual Cone CAI \| BMS Cowl Filters \| Bilstein B8 Struts+Eibach Lowering Springs \|
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04-04-2022, 04:09 PM	#3
Ha4cnn New Member 0 Rep 8 Posts Drives: BMW 328i Join Date: Apr 2022 Location: Toronto Canada iTrader: (0)	Low level coolant That is good to know. Thanks for the post
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