Replaced Coolant Level Sensor...Still Broken

[Crazy 13immer]

I still like the idea of the 6" of electrical tape over the OBC. Its the end to all our problems.

Remember that scene in office space when the printer broke. and he was all like "Why are you telling me paper jam, when there is no F-in paper jam!" Thats like us.

Yeah. My ADD just kicked in. Meh bad.

[turbosporttsi]

i have a great idea! remove the damn thing. OBC-ectomy!

no really though.....would this throw some kind of error message on the dash? i have the same low coolant message, and am thinking of removing the OBC anyway to make room for some guages after my s/c install.

[MR2Rocket]

I'm not at the point where I want to yank the OBC...as a simple daily driver I do use some of its functions. I also think it's nice that there are features like "tail light failure" and "low coolant" to tell people who don't normally check on their cars that they need to do so.

But right now, my main concern is when it comes time for a new Bimmer, I like the peace of mind of selling my car with no warnings or annoying error messages on the OBC...no buyer likes that. I personally know my car is fine on coolant, but that's because I've been dealing with this problem for the past few months.

I just wish someone out there could chime in with a definitive answer. Bleeding the coolant isn't doing anything, there is no air left in my system. The coolant is at the correct marker when the car is cool. I may try replacing the cap as mentioned above, but I'll just say I'm a little skeptical about that at this point.

[JETninja]

Well, My cap was cracked and I replaced it, same error message. My level is fine also, but I will try that running the heater on full and checking it then. I do have a new sensor to install still too....but this thread doesn't give me a warm fuzzy it will work.....

[MR2Rocket]

Well I realized something when I tried re-bleeding today. I ran with the heat on full blast and my heat was...not hot. This means there is still air in the system, blocking my heat.

I don't have a bentley, so my bleeding procedure has been like what was posted here, someone check this and if you know the bentley procedure, post that:

-- Turn heat on full blast, remove filler cap on overflow tank, open or remove bleed screw.

--Run car for a few moments, then press the throttle cable to move through RPMs

--Coolant bubbles come out when RPMs rise, and coolant spills out with the bubbles


That is what I have done now 4 times. Should I drive around with the cap on and bleed screw loose? On my MR2 I had to do that with the rad-cap on halfway to let some air seep out, but the bleeding procedure on a mid-engine car requires hoses and other bleeder valves...not just the one valve and cap on the M3.

Since I think some of my problem may be connected to what seems to be incorrect bleeding, I'm hoping maybe we can get the official procedure up here, and see if maybe we're all just bleeding retards (pardon the wordage )

[MR2Rocket]

Anybody with the Bentley care to share?

[Jeron]

Some models, older M3's, have a bleeder on the thermostat housing.

The Bentley procedure is crap. They don't run the engine with the bleeder open.

The bleed procedure is as described above. Run the hot engine with the heater on and the bleed screw open until the air has escaped.

If you have a lot of air in the system the trick is to remove as much air as possible before bleeding by squeezing the hoses to dislodge it. And if your are doing a coolant change you should pull the upper hose and fill the radiator through the neck and pour coolant down the upper hose.

[LuxoM3]

OK last resort [ without reading the ENTIRE thread ] .... the ground for the Coolant sensor is right behind the Passenger side parking light. There's a next of about 8 common grounds.

Check that for frayed or rotted wiring. Had the same issue on my 1996 M3. The car was in an accident and the knuckle head body shop never repaired the wiring.

[vrsixer]

The car was in an accident and the knuckle head body shop never repaired the wiring.

Same with mine... could the reason I'm receiving that message also...

[kyle242gt]

The POs of my car replaced the sensor twice to no avail. I replaced the thermostat, and now it's all good.

My theory - bad thermostat = slow warmup = OBC thinks there's not enough coolant.

[OnlineAlias]

I have owned 3 of these cars, and all of them have done this at one point or another. My procedure is to keep adding coolant. For some reason, they don't bleed very well and it takes days of topping off coolant. I think the combination of having air in the system and the very effective nature of the reservoir is what does it, ie, the car pushes and loses a ton of coolant to the reservoir when warming up and cooling down. My theory is that it takes a lot of vibration and running for all of the air to work itself out, and I just keep topping the radiator and the reservoir until it stops taking more, even one drop (not in the resevior, obviously. Just fill that to mid cold/warm). It is amazing how much they will keep taking, and keep taking. My first 95 I actually started looking for leaks. Eventually the equilibrium between the amount air/coolant in the heater, engine block, radiator and reservoir is satisfied. This procedure has worked on all of them so far....

[M3Nut]

Okay I'll chime in.

I had this precise problem about a year ago. My coolant sensor warning came on and I thought that's an easy fix. I order the sensor for about $26 and replace it. Flush, bleed, twice, three times to no avail the warning still came on. I checked the wire connection, took a thin file to rough up the contacts, WD40'ed it...still a warning.

So I drained and peered into it and then noticed some hairline fractures in the plastic which divides the expansion tank into separate compartments. Clearly there was some fluid exchange between the two compartments.

So I took the expansion tank out and looked at it more carefully. Yup, in fact there were some small brown plastic slivers at the bottom (you can't see these just from looking from the top if they're there). I shook the tank upside down (took pictures but I can't find them, if I do I'll post them) and several came out.

I ordered a new expansion tank for $70 or so and it came with a new sensor. I replaced and haven't had the problem since. So if you have this problem and you've eliminated the wire connector being a problem, save some time and just replace the whole thing (I don't think you can buy the expansion tank without a sensor).

Good luck.

[Jeron]

My reservoir had a 1x1 piece of brown plastic in the bottom that looked like it might have been a broken portion of the divider but I couldn't be sure it wasn't scrap from the molding process. Someday I guess I'll replace the whole thing.

[MR2Rocket]

I'll check the ground, but is there anything wrong with the bleeding procedure I posted above?

Most people just say let it idle with the bleeder screw open, but that never releases bubbles on mine, I have to rev the car, then I get crazy bubbles for a while.

[M3Nut]

My reservoir had a 1x1 piece of brown plastic in the bottom that looked like it might have been a broken portion of the divider but I couldn't be sure it wasn't scrap from the molding process. Someday I guess I'll replace the whole thing.

Ayup, that's what I found. It is a part of the internal structure of the tank. Once enough pieces break off fluid flows into/out of areas which triggers the sensor warning. That material over time and temperature gets brittle.

[IronButt II]

Weird...

Okay, as for the wires... mine has a brown, and brown/white wire off the sensor. The brown one goes to ground... the brown/white goes off into the tall weeds somewhere. Couldn't find it in the Bentley... at least not where it seems like it ought to be. Suppose you could at least check the ground. Regardless of the wire color... one (and only one) of those guys should be tied to ground.

I live in Arizona... so I tend not to take any chances when it comes to the cooling system. When I began to see this lovely warning... I just replaced the whole thing. But then... my coolant was actually low.

All was fine... for a while. Then the headgasket sprung a leak...

CHECK COOLANT LEVEL... SEE OWNERS MANUAL

[VelocityM3]

There's a good chance that some of your guys issues have to do with cracks in the shitty recycled plastic on the expansion tank and radiator. I thought my sensor was gone and replaced it. Then I saw the small cracks in my cooling system and ended up having to replace my radiator and expansion tank. Got the zionsville kit and it has held up perfectly. good luck guys.

[MR2Rocket]

Problem Solved.

After the 5th bleed/refill of the system, as mentioned above, the warning has gone away. Obviously the bleeding valve on the car doesn't always remove all the air, especially after a full flush/bleed. So after doing it over and over and over again, I guess the car has finally balanced out.

As far as the bad expansion tanks, maybe that's another issue to check with the E36 cooling system. But it seems that for me, getting all the air out took a long time...it's been almost a week since tackling this project, and only know have I removed enough/all of the air to keep the level where it needs to be.

[dfyoung10]

I replaced the upper radiator hose and had to screw around topping off and bleeding air for two days before the warning went away. I didn't run the heater however. Maybe that would have worked better.

[MR2Rocket]

I always ran the heater on full blast, ran the car, idled the car up and down, and had the cap off the tank.

[deen3]

FWIW, i had the same problem for a year. went through everything that has been stated above. i took a closer look at the plastic housing for the 2 wires that connect to the sensor and it was busted. i disassembled it from the wires and plugged the wires directly to the sensor. and secured it with some elec. tape for the time being. I was good for a month.

OBC still displayed "low coolant"...

i found out that the washer sensor has a similar housing for its wires and used it for my coolant sensor.

problem fixed.

now i got to find out why my OBC keeps telling me i have no washer fluid.

[Balthazarr]

Never had this problem and changed radiators 3 times.
Bleeding doesn't have shortcuts.
The last time involved getting a new reservoir and sensor, but never a warning on the OBC.
Either you follow the tried and true directions or you end up with frustration.
Essential to have the heater on full. When you feel the heat in the cabin. You should be done.
Then just top off for a couple of days until the level is stable.

[MR2Rocket]

Never had this problem and changed radiators 3 times.
Bleeding doesn't have shortcuts.
The last time involved getting a new reservoir and sensor, but never a warning on the OBC.
Either you follow the tried and true directions or you end up with frustration.
Essential to have the heater on full. When you feel the heat in the cabin. You should be done.
Then just top off for a couple of days until the level is stable.

I agree, except for your statement about feeling heat in the cabin.

My car would have heat in the cabin, then the next time I went to bleed, would lose it. As you drive your car, air pockets move about the coolant system, sometimes blocking the heater and sometimes not.

The essential thing is to bleed multiple times, even if you dont' get an OBC message. Driving does a lot more to shuffle coolant bubbles than does sitting at idle, or even revving the car while sitting still. It might take a few days of driving to work all the air out, but it eventually will.

I think perhaps one of the large causes for this OBC message is incomplete, rather than improper, bleeding.

[Balthazarr]

Improper bleeding results in incomplete bleeding. Say ya...

[MR2Rocket]

Improper bleeding results in incomplete bleeding. Say ya...

You can bleed the car to perfection, but that doesn't mean you won't have to do it again the next day, and the day after that, for a few days. That's my point...wise guy