Why is there a second expansion tank?

[dan f]

Hi been I while since I have been here.

Hope everyone is well.

I have recently bought a GLE 63S with the M157 motor and I absolutely love this beast! Didn't think it could top the feel of my old ML63 (M156) but in sport + mode it is an absolute HOOT!

So, I was checking out and tidying up the engine bay, (as you do) when I removed the centre engine cowl to discover a second expansion tank with what looks like engine coolant in it.

Can someone please tell me what this is for (my guess is for the intercooler?) and where the fluid level should be when cold?
It seems a little low, but I don't want to add any coolant unless it is necessary.

If it is for the intercooler, is it a separate system or it is part of the wider engine coolant circuit?
If it is part of the wider circuit, then why the need for two tanks?

If it is separate, I want to be sure the coolant is at the correct level.

Cheers in advance.

 

[markjay]

It's for the intercooler... been asked before

I believe that the official name is 'Intercooler Circuit Overflow Reservoir'.

Been added to the M157 in 2012, apparently:

M157 intercooler system updated - MBWorld.org Forums

C218 - M157 intercooler system updated - Wanted to share this info with everyone the new M157 engines has a better intercooler system, the difference is the older system shares the water with the radiator, so both engine and intercooler can be fed by the same top up water tank, this effects the...

mbworld.org

 

[dan f]

It's for the intercooler... been asked before

I believe that the official name is 'Intercooler Circuit Overflow Reservoir'.

Been added to the M157 in 2012, apparently:

M157 intercooler system updated - MBWorld.org Forums

C218 - M157 intercooler system updated - Wanted to share this info with everyone the new M157 engines has a better intercooler system, the difference is the older system shares the water with the radiator, so both engine and intercooler can be fed by the same top up water tank, this effects the...

mbworld.org

Thanks for the reply @markjay .
So is it normal engine coolant in there, as in water mix, or is it a special fluid?
It looks a lot pinker than the fluid in the coolant expansion tank.
I want to top it up but I don't want to put the wrong thing in there.
Cheers.

 

[dan f]

@markjay I think you put up the diagram of the old single tank set up there.

 

[markjay]

It's for the intercooler... been asked before

@markjay I think you put up the diagram of the old single tank set up there.

I think that the diagram shown only the intercooler cooling circuit. Anyway, it's for the thread I linked in my post, so you can read the full post there.

 

[MaxtayE63]

Thanks for the reply @markjay .
So is it normal engine coolant in there, as in water mix, or is it a special fluid?
It looks a lot pinker than the fluid in the coolant expansion tank.
I want to top it up but I don't want to put the wrong thing in there.
Cheers.

Mine is empty also what did you top it up with?