Expansion Tank Floater

[Purplecty]

When I purchased my Imola 4.6, the expansion tank had a hairline crack in it. I replaced it with a used (had slready been replaced but notnsure when as it had old BMW stickers on it) Genuine BMW Made in Italy tank from a friends Imola 4.6 parts car. I noticed the stick on the float is partially missing (seems to be very common) and I am unable to tell what the correct full level is when cold. The past couple days, I have been getting a check coolant error on the cluster but upon restart it never comes back. I check it in the AM on a cold engine and I can always visibly see coolant in the reservoir when opening the cap. I feel this may just be a level sensor issue or just the float getting stuck somewhere causing the error to pop up? There are no leaks at all under and where I park the ground is completely dry...

[crystalworks]

If your cold coolant level is never changing, that's good news. Add a little coolant next time you get the error. If the error goes away it was underfilled. If it's still there, there is a sensor/float issue.

[Purplecty]

If you have a good float with the stick full and not broken can you check to see if you can visually see the level inside the tank on a cold engine so I can use this as a reference?

[crystalworks]

Glad you asked for one. I was running about a half cup - cup low. Not enough to trip the sensor, but nice to top it off. The fluid level was 2-3 inches from the top of the reservoir to get the float to "Max."

[andrewwynn]

The float is part of the sensor. A ring magnet at the bottom floats up and down and closes a switch at the bottom if it gets too low. I suspect the top of your float is broken off and doesn't allow the float to come up properly off the reed switch.

I have 3.0 so can’t help with the cold level photo but somebody should be able to help with that. I would try to resolve what's up with your float: eg drill a tiny hole down into the float and add a stainless screw and piece of straw to guide the float through the hole or just unplug the float sensor to eliminate the error and just regularly check your fluid

[Purplecty]

So I can see coolant but it's definitely not 2-3 inches from the top of the reservoir. I will add it 2-3 inches from the top tomorrow AM on a cold engine. Thank you!

[Purplecty]

Originally Posted by crystalworks

Glad you asked for one. I was running about a half cup - cup low. Not enough to trip the sensor, but nice to top it off. The fluid level was 2-3 inches from the top of the reservoir to get the float to "Max."

It looks like you have the N62 vs my M62 tank?

[crystalworks]

Yes n62. Not sure if they are the same as the M62b46.

[Purplecty]

Yeah I think the levels may be different? Not so sure...

[crystalworks]

Just looked it up. Tanks are different so possibly. Not sure which style floater your tank uses either. Sorry.