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  1. #1
    your temp gauge? Bavarian Cream
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    OK to mix BMW and Prestone coolant? Where is

    Does anybody know if it is OK to mix BMW coolant (blue) with other brands like Prestone (green)?

    Also, where does your coolant gauge go when you drive? I have a 95 740il, and at highway speeds with outside temperature about 40F, the needle drops to the lower 25% mark. If I drive more slowly around town, it will go to halfway point. This bothers me because the 2 BMW 525's I have had stayed pinned at halfway coolant temp after warmup regardless of outside temp, and my E36 325i did the same, so I am worried something might be wrong.


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    Your thermostat may be staying open, not working.

    I would not put the green stuff in your radiator. If you want to use something other that the BMW blue I would use the Xerex G05. It is probably OK to mix that with the BMW.

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    Prestone coolant...

    Prestone is not an approved BMW coolant. Try using Zerex G-48 which is recommend or G-05, any other coolant may be harmful.



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    Re: OK to mix BMW and Prestone coolant? Where is

    I have been trying to figure out the answer to this question myself. I am not sure if Prestone is ok or ?. I don't think the BMW coolant is worth the $$$, IMHO. Please keep in mind I don't own a 740 but 750s. Here is an interesting piece of info I found in the archives. Not sure if it fully answers all of our questions or not but is still worth reading.

    Q: Does Prestone« Antifreeze/Coolant contain phosphates?
    A: Some European automobile manufacturers request that a phosphate-free antifreeze be used in their vehicles. This issue is related to the extremely high mineral content of the water in Europe. If you were to mix an antifreeze that contained phosphates with the type of water they have in Europe, it may produce deposits that can settle in the cooling system and promote corrosion. However, in North America we do not have this type of water problem. Typical North American coolants have contained phosphates (which is part of the corrosion inhibitor package) for many years. Therefore, the question of phosphates is a non-issue here in North America. Prestone« Antifreeze/Coolant is completely safe for use in both foreign and domestic vehicles. For those consumers who would feel more comfortable using a phosphate-free antifreeze, our Prestone« Extended Life 5/150 Antifreeze/Coolant is phosphate, silicate, and borate free. This coolant uses a special chemistry and technology that extends the life of the corrosion inhibitor package so that it lasts for five years or 150,000 miles (whichever comes first), and is safe for all cars and light trucks (old or new). Prestone« Extended Life 5/150 Antifreeze/Coolant has been approved by General Motors under their DEX-COOL« specifications and is compatible with other DEX-COOL« approved coolants.

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    Varied temp reading is not normal

    You are correct to question your coolant temperature reading, which is changing under different driving conditions. The normal reading on the temperature gauge of an e38 is close to center, just slightly right of the picture of the thermometer. It should be stable regardless of driving conditions and outside temperature.

    What you describe seems to indicate a thermostat that is ready for replacement. Here's why:
    - At highway speeds, with the most of amount of air circulating through the radiator fins, the thermostat should close a sufficient amount to reduce the flow of coolant through the engine block and allow the engine to operate at the desired temperature (mid-point on the temperature gauge).
    - During in-town driving, with the reduced flow of air through the radiator fins (largely when the auxilliary fans cycle on and off), the thermostat opens more or fully to allow the most amount of coolant to flow through the engine block.

    That your temperature gauge is reading "normal" during in-town driving indicates that the thermostat is opening fully or close to it. But it's not closing a sufficient amount under other conditions.

    Replacing it is very straightforward. If you get the part from BMW, the thermostat, housing, and temperature sensor are sold as a single part. It's about $50-55 and the unit includes the o-ring for where the housing mates to the top of the water pump housing.

    Hope this information helps.

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    Also, bet your car warms up slowly

    An additional sign of a thermostat that is stuck open or opens prematurely is that your car takes longer than normal for the engine to reach its target operating temperature. An e38 warms up pretty quickly. Within a few minutes of driving, you should see the temperature gauge move and, within a few minutes more, reach a steady position at the mid-point on the gauge.

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    I would not use the GM coolant, I think it is NOT

    approve for BMWs. Use G-05 Xerex.

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    Gauge is conditioned reading

    The coolant temperature gauge on the 7 series id a conditioned reading.
    The gauge will read 12:00 from 75-113-deg.C.

    I assume you have a failed (stuck open) thermostat.
    Rod...
    BMWCCA GGC

  9. #9
    online for thermostat? ctx B Cream
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    Thanks gary and everybody. Is there a procedure

    Is there a procedure online with pics for replacement?

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    Re: Gauge is conditioned reading

    There are three thermostats produced... the least is 175║F, 190║F, and 220║F is the highest... the higher North of the Dixie Line would be using a higher temperature thermostat. BMW... has used same gauge in all modles since the 80's with very little varition such digital or analog readings, and the gauge itself remains analog [for your eyes only instead idiot lights concept].













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    It's amazing to see how many people reply to questions on here and never bother to address the actual question
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