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-   -   getting low coolant level warning (http://www.unitedbimmer.com/forums/showthread.php?t=9249)

ixgarry 10-10-2006 05:12 PM

getting low coolant level warning
I'm getting low coolant level warning at start up and shut down, but level is normal? Haven't done any recent work to radiator or hoses, so there shouldn't be any air locking. Any Ideas??? Temp gauge is around midway.

94bmw325i 10-10-2006 08:52 PM

I got that recently, and just added a little mix of coolant, and it has been fine since, so not too sure. To check the sensor wouldn't you have to drain all your coolant?

bakaroo 10-10-2006 10:42 PM

Oh man, I just dealt with that problem in my car. Does the warning turn off maybe 30 seconds after you start your car/ turn off your car? And when you push the check control, it says everything is fine?

At first (this is after topping off the coolant and that not working) I replaced the all the ties at the end of the hoses, thinking it might be a leak. The warning light kept coming on so then I checked all the hoses and found no tears. I finally just said "F-this" and replaced the entire radiator and sensor (gee, that was fun...NOT) and problem fixed.

Basically, I'd just check the sensor to make sure it's not faulty.

c1apton 10-10-2006 11:09 PM

The actual coolant sensor has corrosion on the threads where it gets it's ground. After it gets a little warm it makes contact. Pull the sensor clean it and re-install.

cainchapman 10-11-2006 01:12 AM

If it is the same style as the E34 sensor, it ages and fails over time. It doesn't cost much to replace and takes about 10 seconds.

Dudesky 10-11-2006 05:56 AM

As you look at the harness at the sensor, feel for a tab underneath. Pull the tab down toward the ground and pull the harness out horizontally. Just clean it off and plug it back in.

coolhandryan 10-11-2006 11:50 AM

Im getting the same warning indicator, it just started doing it a couple of days ago.. where is this sensor/ wiring harness you guys are talking about??


Dudesky 10-11-2006 12:20 PM

It's underneath the coolant expansion tank.

Linds 10-11-2006 05:27 PM

I have this problem but I haven't even attempted reparing it because I'd read before of people that have done everything inclucing replacing the sensor and it still happened. So, I'm interested to know if cleaning it or whatever worked for people.

3050rpm 10-12-2006 08:11 AM

Same phenomenon here, I thought it may have had something to do with the coolant system flush I did over the summer. Proceeding under the adage that there's no such thing as a stoopid question (we all know that's not the case), there's no need to drain any coolant to extract and clean the sensor, is there :dunno ?

Dudesky 10-12-2006 08:49 AM

Okay, here we go. . . hope this explains it clearly enough.

on E36's, 2 things that can cause the OBC warning are the harness or the sensor itself. The easiest is the harness: just untab and pull it out, clean the contacts, and plug it back in. 95% of the time, this is the culprit.

If that doesn't clear up the warning, then it's probably the sensor itself. It's nothing more than a float, not unlike the float in your toilet tank that stops the water when it's full. Except in this case, the level of the float determines the resistance in the electrical circuit of the sensor. This float is like a round cylindrical donut that goes up and down a shaft. If it's not sliding up and down freely, then it gets stuck, triggering the OBC warning. Which means you have to pull out the sensor and clean the debris off the unit- by running it under water and rinsing the crap off. If that doesn't cure the problem, then the sensor is bad. But most of the time it just gets stuck. Problem is, you have to remove the coolant expansion tank to get to the sensor and unscrew it from the bottom. Which means you're gonna lose some coolant, and you'll have to bleed the cooling system afterwards.

I do this procedure every spring, when I flush and refill the cooling system. I've had the same sensor as when I bought the car, and have had no trouble fixing it if/when the OBC warning does come up.

3050rpm 10-12-2006 10:04 AM

Danke vielmals! (By the way, I put in Prestone 5 year/150,000 50-50 premixed. I'm not gonna let it go that far, perhaps 2-3 years.)

ixgarry 10-12-2006 08:56 PM

Couldn't have asked for more!! Great replies.Thanks

Dudesky 10-13-2006 04:50 AM


Originally Posted by 3050rpm
Danke vielmals! (By the way, I put in Prestone 5 year/150,000 50-50 premixed. I'm not gonna let it go that far, perhaps 2-3 years.)

I wouldn't go more than 2yrs, preferrably you should flush yearly. The coolant may last as long as they say, but you still need to flush out the crud and particulates that accumulate in the system. Thats the part they don't tell you, because it has nothing to do with the performance of their product :)

3050rpm 10-13-2006 08:19 AM

Yes, I agree. My routine is to drain the old stuff out, then refill with Prestone Radiator Flush and distilled water; drive the car around the block a few times to get that stuff well circulated; then drain that stuff out and then put in the new coolant. The last time I did that the second draining in the process came out quite clear, plus with the modern compositions of the coolant these days to inhibit corrosion I figure I'm good for two years. By then the tendonitis in my left forearm from reaching up to get at that engine block drain plug should be healed enough to have another go at it :rolleyes.

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