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Thread: Coolant: how low is too low?

  1. #1
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    Coolant: how low is too low?

    Ok so the "coolant level low" warning is supposed to come on before it's dangerously low but when does that actually happen? I checked my reserve tank and my coolant is so low that I can't press the measuring stick down anymore. In fact it's low enough that I could see most of the stick and a bit of the base. If I had to guess its definitely 60% empty, maybe even 70-80%.

    So yea...how much lower can this go? I want to flush it all out sometime in the near future and refill it with BMW-approved coolant.

  2. #2
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    Is this thread serious? I mean, how come you're running low on coolant to the point where the expansion tank is almost dry, and you still want to know how low could it go???

    Go right now to the car and add some water until the stick reads the right level. You don't always need to use pure coolant if it's just to keep the thing from overheating and if you don't want to spend money only to flush it later. Bottled coolant is a mix of water with chemicals anyway, so adding a few ounces of water would have almost no effect on the coolant properties.

    Your car will tell you it's running low on coolant when the expansion tank is around the 1/4 mark. Less than that and you're risking destroying your engine.
    Last edited by crdiscoverer; 08-24-2010 at 05:30 PM.
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    Quote Originally Posted by crdiscoverer View Post
    Is this thread serious? I mean, how come you're running low on coolant to the point where the expansion tank is almost dry, and you still want to know how low could it go???

    Go right now to the car and add some water until the stick reads the right level. You don't always need to use pure coolant if it's just to keep the thing from overheating and if you don't want to spend money only to flush it later. Bottled coolant is a mix of water with chemicals anyway, so adding a few ounces of water would have almost no effect on the coolant properties.

    Your car will tell you it's running low on coolant when the expansion tank is around the 1/4 mark. Less than that and you're risking destroying your engine.
    Well obviously my car hasn't told me Thus the thread

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    too low is when you fry the engine conducting an unnecessary experiment.

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    Quote Originally Posted by nubreed000 View Post
    Well obviously my car hasn't told me Thus the thread
    It wasn't clear from your post.

    If your expansion tank is dry and the warning never showed up, then your coolant level sensor is bad. I had to replace mine a few days ago, only that it was reporting the level as low when it was indeed fine. Again, at about 1/4 level you get the low coolant warning. Max level is around the 3/4 mark.
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    Quote Originally Posted by nubreed000 View Post
    Ok so the "coolant level low" warning is supposed to come on before it's dangerously low but when does that actually happen? I checked my reserve tank and my coolant is so low that I can't press the measuring stick down anymore. In fact it's low enough that I could see most of the stick and a bit of the base. If I had to guess its definitely 60% empty, maybe even 70-80%.

    So yea...how much lower can this go? I want to flush it all out sometime in the near future and refill it with BMW-approved coolant.
    Some people wonder why they overheat and blow they're engine. When clearly it's neglect.perfect example of a poorly maintained e39.

  7. #7
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    do all of these cars have a level sensor? I thought just the newer ones did.
    >'97 528i, 200000 miles, Hella Xenons, 17" Stilauto wheels, Vogtland Drop Springs, Dynomax Race Muffler, Homelink, 540 brake upgrade, 15mm spacers >'65 & '74 MG Midgets BFC OT Lego Club #48 Manual conversion in process!!!



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    I'm going to start a thread entitled: "Why are the call 'Idiot lights'?"

    Often when these lights come on, it's too late.

    Also, the coolant level sensors often fail, as they are exposed to corrosive fluids. My e36 sensor failed, but I routinely check the level (along with oil, etc...).
    Last edited by 325icintn; 08-24-2010 at 06:27 PM.

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  10. #10
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    Quote Originally Posted by NNY528I View Post
    do all of these cars have a level sensor? I thought just the newer ones did.
    Mine has a level sensor, and it's a build date 12/96. I have a semi-transparent expansion tank with no floating stick. Cost me about $30 to replace. The sensor is a floating device that screws to the bottom of the tank.

    Part #13:
    Last edited by crdiscoverer; 08-24-2010 at 06:50 PM.
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  11. #11
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    Only certain US 528s had them per RealOEM

    http://www.realoem.com/bmw/showparts...35&hg=17&fg=05
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    My plan is to never have to see the idiot light by regularly checking fluid levels.

  13. #13
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    i was actually shocked at how low it was. i check on it from time to time, but i was gone for about a month and haven't checked since early june. can't believe how low it is now.

    anyhow i poured some distilled water in and after the weekend i'll get it properly flushed and refilled.

  14. #14
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    Quote Originally Posted by nubreed000 View Post
    i was actually shocked at how low it was. i check on it from time to time, but i was gone for about a month and haven't checked since early june. can't believe how low it is now.

    anyhow i poured some distilled water in and after the weekend i'll get it properly flushed and refilled.
    I keep a bottle of premixed coolant (50/50) in the car at all times.

  15. #15
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    Quote Originally Posted by jamesdc4 View Post
    I keep a bottle of premixed coolant (50/50) in the car at all times.
    yea it's been on my list of "Essential Items in my car" that I haven't actually put in yet.

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    Quote Originally Posted by jamesdc4 View Post
    My plan is to never have to see the idiot light by regularly checking fluid levels.
    My plan is to keep letting the lights pile up until I dont have to decorate anything when Christmas rolls around

    Going into my TENTH YEAR of providing high quality reproduction BMW fabrics!

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    Quote Originally Posted by blackxs View Post
    My plan is to keep letting the lights pile up until I dont have to decorate anything when Christmas rolls around
    hahaha, 2 for 2 in this thread so far, keep em rolling, lol

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    In the US ONLY E39's with the HIGH OBC get a coolant level sensor. Most early M52/M52TU E39's don't have the HIGH OBC. I doubt your '00 528i has the low coolant level sensor. This is one of the DUMBEST moves BMW ever made in view of E39 cooling system weakness'. I'm attempting to retrofit one into mine. The expansion tank is factory ready for sensor. I can't decide between tieing into low washer fluid or brake fluid light circuit.

    Paul S
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    Quote Originally Posted by nubreed000 View Post
    Ok so the "coolant level low" warning is supposed to come on before it's dangerously low but when does that actually happen? I checked my reserve tank and my coolant is so low that I can't press the measuring stick down anymore. In fact it's low enough that I could see most of the stick and a bit of the base. If I had to guess its definitely 60% empty, maybe even 70-80%.

    So yea...how much lower can this go? I want to flush it all out sometime in the near future and refill it with BMW-approved coolant.

  19. #19
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    Quote Originally Posted by pshovest View Post
    In the US ONLY E39's with the HIGH OBC get a coolant level sensor. Most early M52/M52TU E39's don't have the HIGH OBC. I doubt your '00 528i has the low coolant level sensor. This is one of the DUMBEST moves BMW ever made in view of E39 cooling system weakness'. I'm attempting to retrofit one into mine. The expansion tank is factory ready for sensor. I can't decide between tieing into low washer fluid or brake fluid light circuit.

    Paul S
    BMW CCA 69606
    Wow, I have to agree with you on that. Given how stupidly prone to failure these systems are, not including a level sensor is probably the most idiotic thing I have heard about our cars. As I said above, my car is a 12/96 build date and has the sensor, but it also has a High OBC. In other parts of the world it wasn't year related apparently.
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    Quote Originally Posted by pshovest View Post
    In the US ONLY E39's with the HIGH OBC get a coolant level sensor. Most early M52/M52TU E39's don't have the HIGH OBC.
    I know the e36 m50 cars had a coolant level sensor. My only guess it that they did not have a spot on the standard e39 instrument cluster and did not want to tie it to the mid-obc. Really poor decision making. As great as the e39 is, the mid-90s management of BMW did not make the best decisions.

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