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Old 11-27-2010, 06:56 PM   #1
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Low coolant problem, whats best vs worse case scenario?

Hey guys,

I have a 2003 bmw 325i with 160k on it. My low coolant light came on yesterday so i filled it up, and a day later it is down again as i just randomly checked it.

this happened to a friend of mine and it ended up just being the cap that cracked on top where u refill (she paid 50$ to replace it).

I dont see any spills or leaks at all from what ive checked.. so im thinking it could be the cap, and it burns as im driving.

IF it indeed is a tank, its a few hundred bucks to repair. I dont know too much about this but whats the best vs. worse case scenario of this problem?

Thanks all!
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Old 11-27-2010, 07:06 PM   #2
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Check the thermostat that is inserted in the lower radiator hose.

The o-ring in these goes bad and they seep. You can see it with a flashlight and replace it by hand in about 10 min. Cost is 25-30 usd.

I was getting low coolant and this stopped it!
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Old 11-27-2010, 11:32 PM   #3
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Could be all kinds of things. If you don't have any of the tools to diagnose it, you could try the following simple step to try and narrow it down. Take off the shield on the bottom of your car, and then drive around a bit to get your car up to normal temperatures. Then park, wait a bit, and see if you find any coolant puddles. That's how I was able to locate my last leak. Also, look for whitish buildups on your expansion tank. Sometimes, cracks expand when your engine is heated up but then disappear once it cools, so you wouldn't see them directly when looking at a cool engine. Those white deposits are the remains of the coolant leaking out.
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Old 11-28-2010, 08:14 AM   #4
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pull the engine oil dipstick to ensure the coolant is not leaking into the oil pan from a cracked head or bad head gasket. if there is any in there, should be able to smell it or see it on the dipper.

but, the worst case scenario is a seized motor from excessive overheating - bad... very bad.
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Old 11-28-2010, 08:22 AM   #5
Zero. Leaks.
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Worst case if your car over heats and your engine turns in a block of scrap metal.

Best case if you buy the tank for $60 online with some BMW coolant for $20 and you install it yourself. my friends tank popped out and he needed me to help him. I've never installed the tank before but I got it on with no problem.
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Old 11-28-2010, 12:53 PM   #6
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yeah i think it may be the o-ring because theres always a few drops on cardboard (which i place under my car) and its right under the left side of the engine where the o-ring is. nothing else majorly wrong with it.. that i can see... no coolant in the motor oil etc.

Last edited by charlesrock; 11-28-2010 at 12:59 PM.
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Old 11-28-2010, 10:59 PM   #7
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I would follow jakes advise and change those parts as they break very often.. when was the las time you did your cooling overhaul?
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Old 11-28-2010, 11:04 PM   #8
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i did my tensioners, belts, pulleys, thermostat was done... and yea i think i narrowed it down to either the o-ring/hose or the expansion tank. has to be one of those. best case the cap but i doubt it. I kept my car sitting for two days now and the coolant level went down a centimeter or two.. so must be a slow leak somewhere in those places
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Old 11-29-2010, 02:01 PM   #9
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looks like i was wrong.. its a leak from the thermostat housing it appears... mechanics working on it
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