M54 coolant- not seen this before?

bigwinn · Post by **bigwinn** » Wed Oct 27, 2021 10:49 am

Morning all

Finished the vanos marathon on the aero car

Final piece of the puzzle was as always a new expansion tank. Fitted and done, used the old level sensor.

Restarted the car and all good apart from showing a coolant level light and cant get the heater to blow hot.

So this am, I took the old sensor out and fitted the new one supplied with the expansion tank: fully expecting to get a face of coolant!

But no- swapped them over dry as a bone? Reconnected and there is still a level warning light

So- aside the point I clearly have an air pocket somewhere preventing the heating to work- WTF is with the level sensor and expansion tank??

Cheers

Stuart

patriot66 · Post by **patriot66** » Wed Oct 27, 2021 12:44 pm

Hi Stu. Have you got the front of the car raised when bleeding ? I always have the front of mine on ramps or axle stands when I bleed it and never had an issue

bigwinn · Post by **bigwinn** » Wed Oct 27, 2021 12:50 pm

Hi Si!

Yes all raised up

Going to give it another blast this afternoon

Only difference was 5L out but about 5.5L in?

Why is no coolant pouring out when I take the level sensor out though? I can’t get my head around that?

Level is high in the expansion tank? Is it possible I’ve got an air pocket in there?

enuff_zed · Post by **enuff_zed** » Wed Oct 27, 2021 1:30 pm

Hi Stuart,
Ratcatcher cut up my old one. The sensor sits in an outer pocket. This is surrounded by a float with a magnet in it that actuates the reed switch in the sensor.
This float moves in its own chamber which is only about 1/4 of the height of the tank, so it only starts to move when the coolant is very low.
The float that pops out the top is a visual guide only. This only goes down to about 2/3 of the tank level. In other words, if your pop up float bottoms out, you still could have 1/3 tank of coolant in there.
I always assumed the pop up float activated the switch when it dropped right down, but the two are completely segregated.

Chop up your old tank, it's quite complex inside.

bigwinn · Post by **bigwinn** » Wed Oct 27, 2021 1:35 pm

Wow!!

Off to get the Dremel to investigate

Cheers!!!

enuff_zed · Post by **enuff_zed** » Wed Oct 27, 2021 1:49 pm

bigwinn wrote: ↑Wed Oct 27, 2021 1:35 pm Wow!!

Off to get the Dremel to investigate

Cheers!!!

It seems a real piece of German over-engineering. Shame the plastic didn't live up to the design ethos.

Scooba_Steve · Post by **Scooba_Steve** » Wed Oct 27, 2021 4:49 pm

enuff_zed wrote: ↑Wed Oct 27, 2021 1:49 pm It seems a real piece of German over-engineering. Shame the plastic didn't live up to the design ethos.

Scooba_Steve · Post by **Scooba_Steve** » Wed Oct 27, 2021 4:49 pm

bigwinn wrote: ↑Wed Oct 27, 2021 1:35 pm Off to get the Dremel to investigate

bigwinn · Post by **bigwinn** » Wed Oct 27, 2021 5:26 pm

Scooba_Steve wrote: ↑Wed Oct 27, 2021 4:49 pm
bigwinn wrote: ↑Wed Oct 27, 2021 1:35 pm Off to get the Dremel to investigate

Got sidetracked

Will get brutal tomorrow

Z4ZeeGermans · Post by **Z4ZeeGermans** » Sun Oct 31, 2021 11:00 am

bigwinn wrote: ↑Wed Oct 27, 2021 10:49 am Morning all

Finished the vanos marathon on the aero car

Final piece of the puzzle was as always a new expansion tank. Fitted and done, used the old level sensor.

Restarted the car and all good apart from showing a coolant level light and cant get the heater to blow hot.

So this am, I took the old sensor out and fitted the new one supplied with the expansion tank: fully expecting to get a face of coolant!

But no- swapped them over dry as a bone? Reconnected and there is still a level warning light

So- aside the point I clearly have an air pocket somewhere preventing the heating to work- WTF is with the level sensor and expansion tank??

Cheers

Stuart

Well, if my situation turns out to be an air lock of some sort, I believe M54 is a b*stard of a thing when it comes to draining and replacing the coolant. I've noticed something similar when I changed the exp. tank (I also used the old sensor): the heater was mildly cool on passenger side but hot on the driver's side. I had to make sure I got all the air out (which was not a quick ordeal) and add back some deionised water for the heater to even out. Even then, as you've seen on my other thread, I may have had a persistent air lock in the system. I wish I had a Z4 with an electric water pump to be honest...

bigwinn · Post by **bigwinn** » Sun Oct 31, 2021 12:59 pm

To be fair this is the first time I’ve had an issue bleeding- my own fault as I had the front up on axle stands as opposed to ramps-

Chris_D · Post by **Chris_D** » Sun Oct 31, 2021 1:33 pm

I've had an ongoing issue with my heating which I'm putting down to an air pocket trapped in the coolant loop.
I either get hot air or cold with not much temp regulation possible in between.
Need to try yet another bleed / top up at some point...

enuff_zed · Post by **enuff_zed** » Sun Oct 31, 2021 3:50 pm

bigwinn wrote: ↑Sun Oct 31, 2021 12:59 pm To be fair this is the first time I’ve had an issue bleeding- my own fault as I had the front up on axle stands as opposed to ramps-

Did you get a chance to check out that expansion tank construction?

bigwinn · Post by **bigwinn** » Sun Oct 31, 2021 8:02 pm

Still saved in the pile of stuff to do!

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