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Hello All,

I had to create an account for my issue as I could not find a good place to start to troubleshoot my problem. This monday I had the coolant light come on my 2004 X3 on the way home, for the first time. I parked it and let it cool over night, the next morning I checked it again and the level was where it needed to be, so i put a little bit of distilled water.


The light would come on and off, and after some research believed to be in correlation to the coolant level sensor. I was going to replace it today, though when i was driving up my neighborhood, the temperate gauge beeped real loudly and slammed to red. I immediately stopped and turned off the car. I turned it back on and the temp gauge was back in the middle.

It is in my driveway now and dont plan to drive it till the overheating symptom is addressed first, and waiting for it to cool down at the moment. Does any one know what can be my culprit if the coolant level is still at the right level? I will replace the coolant level sensor, and then where should i look in regards to the over heating?

Thanks.
 

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I'd guess more likely the water pump and/or thermostat is shot. Also check your cooling fan.
 

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Yes, that will show if the fan works while the AC is running, but it doesn't insure that the fan runs with the AC off. There's a separate control circuit for that, typically with a "low speed" relay (high speed for AC) and a temperature sensor. Fortunately my X3's are fine, but a 325 and a Ford were a PITA to diagnose in the past! (325 had a bad low-speed resistor.)

What year is your X3?
 

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Yes, that will show if the fan works while the AC is running, but it doesn't insure that the fan runs with the AC off. There's a separate control circuit for that, typically with a "low speed" relay (high speed for AC) and a temperature sensor. Fortunately my X3's are fine, but a 325 and a Ford were a PITA to diagnose in the past! (325 had a bad low-speed resistor.)

What year is your X3?
its a 2004. Just ordered a new water pump, thermostat, and expansion tank w/ coolant sensor (address coolant light). I will replace everything over next weekend, hopefully this will address both my issues. Will keep updated.
 

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Unless you have a MT you will probably need a new AT thermostat when replacing the expansion tank - unless you are able to pull or press it up really straight and carefully.

Technically, if you just wanted to try replacing the coolant level sensor that can be done w/o draining coolant as it fits in a dry cavity in the expansion tank and monitors position of the float in its chamber via magnetic attraction.
You could even borrow the level sensor from your washer tank as it is the same part # I believe.

However, you have some other strange goings on with the temp. gauge jumping to red and going back on immediate restart.
Tread carefully as this could be local overheating caused by lack of coolant flow or air flow (as mentioned by BMWaufKS). A detailed diagnosis is the best plan.
 

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Discussion Starter #7
Tread carefully as this could be local overheating caused by lack of coolant flow or air flow (as mentioned by BMWaufKS). A detailed diagnosis is the best plan.
What year is your X3?
Thanks, the engine had just cooled down and opened up the expansion tank, and low and behold it was low. Top it off and bled the system, took it for a drive till the engine temp. was at 12 o clock position and the light has not come back on.

Im going to leave it overnight and check the coolant level tomorrow morning. Could air in the system cause it it to slam to red?
 

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Could air in the system cause it it to slam to red?
Yes. Follow the recommended bleed procedure.

You have some good parts on order -- if they haven't been replaced in recent years, good to do them! Flush and fill too.
 

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I just tested it by opening the bonnet, switching the aircon on and seeing if it span. Not much else you can really do
thanks, I will test it out this afternoon. As for the water pump, it seems there is no real way to test it correct? From my research it seems you either replace it as a pre-maintenance thing or once it goes it goes.
 

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I'm unsure on the water pump but it's a simple check on your fan, let's face it when the needle rises the fan should come on, mine didn't and I spent a bit of time looking at other parts for it just to be the fan. Good luck matey, keep your thread updated
 

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I'm unsure on the water pump but it's a simple check on your fan, let's face it when the needle rises the fan should come on, mine didn't and I spent a bit of time looking at other parts for it just to be the fan. Good luck matey, keep your thread updated
Yes. Follow the recommended bleed procedure.

You have some good parts on order -- if they haven't been replaced in recent years, good to do them! Flush and fill too.
Just following up, i bled the system and the coolant light came off and the car has not overheated since. Though today When i started it up the coolant light came on, but once the engine got up to temp it went away.

I am at work but will check the car after once its cooled down, but it seems i might have a leak somewhere which is another issue. Though if the coolant is at the right level, would this be the coolant level sensor which is the issue?
 

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Make sure of the basics first: water pump, t-stat, hoses, coolant, and cooling fan. Blaming the sensor first is like blaming your house's thermostat first when it's actually a dead AC unit.
 

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Make sure of the basics first: water pump, t-stat, hoses, coolant, and cooling fan. Blaming the sensor first is like blaming your house's thermostat first when it's actually a dead AC unit.
ok thanks i will look to see if there is a leak some where, i think i may have to remove the splash shield to take a look under, as i recall last time i checked I did not see anything from under the hood.

thanks again for all the help
 

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You can see the sides of the expansion tank from above if you get your sightline at the right angle. A flashlight and inspection mirror helps.

Look for white stains on the black plastic especially at the corners or anywhere the plastic curves.

Don't think you would be able to check much more from underneath with the pesky shield removed except the blue drain plugs and the bottom hose, and maybe the AT cooler.
 

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Did you check the fan?
Yup checked the fan both on idle and with AC, it works.

Make sure of the basics first: water pump, t-stat, hoses, coolant, and cooling fan. Blaming the sensor first is like blaming your house's thermostat first when it's actually a dead AC unit.
You can see the sides of the expansion tank from above if you get your sightline at the right angle. A flashlight and inspection mirror helps.

Look for white stains on the black plastic especially at the corners or anywhere the plastic curves.

Don't think you would be able to check much more from underneath with the pesky shield removed except the blue drain plugs and the bottom hose, and maybe the AT cooler.
Just checked the expansion tank and the bobble is where it is suppose to be at the second knob, i believe it is in fact the coolant level sensor. I will look with a flashlight though for any cracks and white mark stains.

thanks everyone!
 
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