"Check coolant" message even though float stick is above rim

[Stilllearning6]

1998 740iL :

new water pump, belts, hoses, coolant, expansion tank, radiator, coolant level sensor, brass bleed screw
Bled air 5 times--> seems OK.
Great heat.
Temperature gauge holds at the noon position , so I am happy.

Why is "check coolant level" message appearing?

Put in 2 coolant level sensors in the past 2 years.
Red float stick is above the rim ( too much coolant) each cold morning.
I can not see the coolant when I look into the expansion tank, but when I push the bobber stick down, it springs up proudly.
I believe that I have more than enough coolant.

A search in this forum revealed others with same issue were advised to replace coolant level sensor or they were advised that they still have air in the system.

How would air in the system trigger " check coolant level" if the float stick is bobbing way up high?

Is there some other known electrical issue in the check coolant level circuit ?
I am leaning toward a faulty circuit rather than 2 bad coolant level sensors.
Can the experts educate me?

[Timm]

Did you use an OEM expansion tank?

[Stilllearning6]

Expansion tank : Behr $37
Coolant sensor : Febi $5

[racer2086]

You need a new expansion tank. Something internal with the float is broken. Usually it's at the age where the plastic is starting to get brittle, and if you mess with the stick, it'll fall off the float and may even break.

My new Behr expansion tank came with the coolant sensor. Took me about 20 minutes to install without draining the cooling system -- just have a pan to catch what's in the tank and what dribbles out the hose before you plug it or crimp it off.

[georgebest]

You need a new expansion tank. Something internal with the float is broken. Usually it's at the age where the plastic is starting to get brittle, and if you mess with the stick, it'll fall off the float and may even break.

My new Behr expansion tank came with the coolant sensor. Took me about 20 minutes to install without draining the cooling system -- just have a pan to catch what's in the tank and what dribbles out the hose before you plug it or crimp it off.

Agreed has to be the tank, I have also just installed recently a Behr. It's all great with the exception that the bleeding screw tab is not fitting on it, but just chipped the tab off a bit and now fine.

[racer2086]

Hmm didn't have that issue when I recently installed mine...

[georgebest]

Hmm didn't have that issue when I recently installed mine...

Strange, maybe I got faulty one. The genuine BMW tab on the top, the one that goes below the bleeding screw is not fitting on it. It's probably a mm off, anyway just cut it off from the tab not a big deal. Wasnt worth the trouble for sending it back.

[racer2086]

Are you talking about the tab that fits around the bleed screw and presses into the expansion tank from above the shroud? If it doesn't fit, you are likely having some minor interference issues with the hose clamp that connects the expansion tank tube. This will keep things from sitting down properly.

[georgebest]

Are you talking about the tab that fits around the bleed screw and presses into the expansion tank from above the shroud? If it doesn't fit, you are likely having some minor interference issues with the hose clamp that connects the expansion tank tube. This will keep things from sitting down properly.

That's the one.
It's a size issue, the tab is slightly wider than the gap on the tank. It's just a millimeter though but enough to keep it from going in. I'm away from my car and cant make pictures. I think the gap on the Berth tank is just not the proper size, at least on mine.

[racer2086]

Oh hmm. It's a really tight fit, but maybe your tank is slightly off. Who knows

[Stilllearning6]

During last 6 months, hardly drove E38 due to " check coolant level" message kept appearing after several minutes at idle or driving. Each time I checked a cold engine coolant level, the bobber was above the rim, definitely not low level.
Searching in this forum taught me that the sensor was a likely culprit and at $7 -$13 to replace, it was a relatively inexpensive fix.

Replaced with $13 Meyle sensor and message still appears
The expansion tank is new , so I discounted the theory of old brittle , faulty expansion tank with corroded terminals.

Any suggestions to dx the issue?

My understanding is that the expansion tank has a circular ring-like float ( circular life preserver style) that should travel up/down a pole.
Does that float ring get hung up in a new expansion tank?
Is there another faulty electrical component to check?

I dread needlessly switching the expansion tank again for 3rd or 4th time. I have 2 in the garage.

[racer2086]

Generally my experience is that the expansion tank is the reason, but air could be another one. If you start the car with the cap off and/or let the car warm up with the cap off, you may notice at one point the level in the tank drops significantly as the car sucks the coolant in from the expansion tank. That's what I've noticed with my car. The bobber on my expansion tank usually sits well above the rim even when this happens. I have come to conclude that something with the float system is off and causing the car to either read over-full when its not or that the expansion tank isn't keeping the coolant it is supposed to have in there.

[Stilllearning6]

More data:
I drove around town for 1/2 hour and the CCL message appeared (within 3-4 minutes, I believe).

When I returned home, I turned car off and let the CCL light go out within a few minutes; engine still at operating temperature.

Started warmed up car, let idle 5 minutes--> no CCL light appeared.

Issue is intermittent.
What does that clue provide?

During the fall, I spent considerable time bleeding the coolant via the bleed screw to be certain air was out.
That was a tedious process that seemed to go on endlessly.
Never really know for sure when it is no longer bubbling through bleed screw.

Dash temp gauge appears to never go beyond noon position , so I am happy that engine temp does not get too high.

Willing to be educated as to why the CCL message appears sporadically. Once it comes on , it stays on until I turn off car.
Then, it is gone for a few minutes at idle or driving, and then it reappears .

[racer2086]

I had the same exact issue with my car. No message if the coolant was hot. I replaced my expansion tank with OE / OEM and no more issues.

[Stilllearning6]

Is the Behr expansion considered OEM?
I purchased several expansion tanks and still have them.
Will need to check brans on each of them.

It is my understanding that you replaced your expansion tank with a new one ( which brand? ) because you received CCL message .
After you swapped the expansion tank, the CCL message no longer falsely appeared.

If that is the answer, I will probably wait until spring weather to attempt the swap of the expansion tank.
It takes me almost all day as I usually encounter great difficulty in removing the expansion tank hose that resides above the radiator and gloves over a weak plastic nipple on the radiator driver side top. Additionally, the numerous electrical connectors and hoses have always been particularly difficult to R/R, nothing like easy American cars. Then, the bleeding numerous times...

[franco90]

I get this message as well and nothing mine is all top off and all OEM , this happens once in a while any ideas

[racer2086]

Is the Behr expansion considered OEM?
I purchased several expansion tanks and still have them.
Will need to check brans on each of them.

It is my understanding that you replaced your expansion tank with a new one ( which brand? ) because you received CCL message .
After you swapped the expansion tank, the CCL message no longer falsely appeared.

If that is the answer, I will probably wait until spring weather to attempt the swap of the expansion tank.
It takes me almost all day as I usually encounter great difficulty in removing the expansion tank hose that resides above the radiator and gloves over a weak plastic nipple on the radiator driver side top. Additionally, the numerous electrical connectors and hoses have always been particularly difficult to R/R, nothing like easy American cars. Then, the bleeding numerous times...

Behr is OEM. That is what I used. I keep an extra one on hand for when they crack. They are ~$35 from FCP.

Replacing them should not be that involved. I can do it in 20 minutes without draining coolant. Here's how:

Get your new expansion tank unpackaged and have it easily within reach to your old tank.
Remove the MAF, air filter, and tubing to have easy and clear access to the expansion tank.
Remove the plastic tab that secures the expansion tank to the fan shroud.
Remove the two plastic push rivets that secure the fan shroud to the radiator.
That will give you clearance to lift the fan shroud up and access the small hose that hooks onto the expansion tank. Disconnect that hose at the expansion tank and get a typical screw-type hose clamp to put it back on with.
Disconnect coolant level sensor plug. Your new Behr tank will have a new sensor in it.
Get your coolant catch pan and place it under the expansion tank where the lower hose connects.
Loosen hose and slide it almost all the way off. Twist the hose so the coolant in the expansion tank can pour out in a controlled stream into your catch pan.
Once the stream ends, quickly pull the hose off the expansion tank and either crimp the hose with your hand or block to off so coolant does drain out the hose.
Pull the old tank out, and grab your new expansion tank that is within reach and stick the hose right on.
Hook everything up in reverse and fill the coolant from the pan back into the tank. Done.

[Stilllearning6]

Thank you for the feedback on the Behr expansion tank; that it is considered OEM.

You are a better man than I as you can do this in 20 minutes. Hope it goes as smoothly as written.
The disconnect of the expansion tank nipple hose and the disconnect of the lower hose has usually been problematic.
Last time, I lubed the lower hose with silicon brake grease to prevent it from sticking on the expansion tank.
The expansion top clip clip has already snapped once before, a side rivet snapped and the snaked hose that runs along the top of radiator cause the radiator right angle nipple to snap.

These parts were replace less than 1,000 miles ago.
Temp is 23 degrees on driveway so I will wait for spring.

[racer2086]

Oh that is cold. I don't miss those CT winters. It helps to work with the engine a little warm. Your hands don't get quite as cold.

The key is to get that upper small hose off the tank first before pulling the tank away from the shroud. Remove/loosen the clamp, take a large screwdriver (turn it 90* if you have to) and pry. Then just leave the hose sitting there on top of the radiator.

The clip for the expansion tank and that 90* elbow that you mention for the small hose can be purchased separately. They are cheap, so I buy multiple and have them on hand, just like the oil filter housing bushings. I leave them all in the trunk.

For the lower hose, take your hand, grip it, and twist until you break the seal. Then it'll be a piece of cake to walk that off the tank.

The nice thing about working on the top hose first, is that you lose no coolant and if you get stuck, you bail and you're no worse for wear. But the factory crimp hose clamps suck and make it impossible to get that hose off. You have minimal coolant loss pulling the lower hose of the tank if you drain what's in the expansion tank and plug the hose end so nothing flows out of the engine. The tank will lift right out once the fan shroud is out of the way enough.