M54 coolant- not seen this before?

bigwinn

bigwinn

Elite
 Lincoln UK
Site Supporter
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
 
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 :thumbsup:
 
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?
 
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 said:
Wow!!

Off to get the Dremel to investigate

Cheers!!!
Click to expand...
It seems a real piece of German over-engineering. Shame the plastic didn't live up to the design ethos. :roll:
 
bigwinn said:
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
Click to expand...

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...
 
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-
 
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...
 
bigwinn said:
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-
Click to expand...
Did you get a chance to check out that expansion tank construction?
 
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