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Sunday I didn't use my car. At 9pm I moved it across the street because the street sweeper was passing on Monday. Monday morning at 8:30am my car doesn't start.

I remembered that I haven't checked to make sure I have coolant in a while. I had zero but my car never signaled that it was overheating. At 4:30pm my friend gave me a jump start. I let it run for 15 minutes. Turned it off and back on 15 minutes later and it worked fine. By this time I didn't have to go anywhere so I just left it. Today at 8:30am it wouldn't start again. Is it that I damaged something because I didn't have any coolant, or is it my battery?

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The car doesn't start, but what systems are still working? Does the engine turn? Does the starter motor engage? Do the lights work? –  vlsd Oct 30 '13 at 17:03
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When you say you had zero coolant, you mean that there was no coolant visible in the coolant "bottle," or that you opened a coolant drain at the bottom of the system and nothing came out? If merely no coolant visible in the overflow bottle, then you were likely low on coolant, but not out of coolant. Either way, wouldn't prevent you from starting the car unless there had been some serious drama (major overheating) the last time the car ran. This would not have gone unnoticed. –  mac Nov 1 '13 at 15:50

2 Answers 2

If jump starting works, it has nothing to do with the coolant. Though coolant doesn't usually just go missing; it's (supposed to be) a closed system. That's worth addressing, too.

Quick DIY test to see if the problem is the battery or the alternator:

-Go to the hardware store (or ideally the nearest harbor freight tools) and buy a $10 volt meter. Digital is better.

-Jump start the car, let it run for a few, and measure the voltage between the (+) and (-) terminals of the battery

-If voltage is between 13.5-14.5 the alternator is fine and you need to replace the battery.

-If voltage is less than 12 the alternator isn't doing its job to charge the battery.

-There is rarely a middle situation between 12 and 13.5, but if that's what you get, watch it and see if the voltage is climbing or falling. Falling: bad alternator. Climbing gradually or constant: Likely a bad battery and a weak alternator together.

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Coolant has nothing to do with your car's ability to start. Most cars can be started with the water pump not even running (not for long, mind you, as it will overheat).

You said you needed a jump to start once -- I'd imagine your battery needs replacing.

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