Urgently need to know if the big white tank in the engine compartment (with the big screwcap) is where I fill with water (on the left).

This is one of the Limo's from work & I think I over-revved it (& it overheated) as there was a pool of water leaking underneath.

Car specialists please help me as I need it for later & if I can't use it I'm in deep shit. I think it is the tank & I'm just being hesitant about filling in case it isn't the right one, but I'm 90% sure it is.

It's the W220 model.

The pool of water under the car is from the air conditioning, and is quite normal. The big white tank is probably the screen washer bottle.

I would not touch either without reading the handbook: maybe it's in the glove compartment?

I am fairly certain the car is ok. Just drive it unless warning lights come on, then stop and call the TCS.

1) Does the cap have an overflow valve or outlet ?
2) Does the reservoir (the bottle with the cap) have any gradation marks (Empty, full, half) etc ?
3) Can you trace a hose from the bottle to the radiator ?

If you can (3) then most likely this is the right reservoir.
Le the engine cool down. Don't go near the radiator cap if it has one. When cool, top the reservoir up to the full mark, replace the cap, start the engine and let it idle for a while, cool again, and re-check / refill the bottle to the full level.

Hopefully you are seeing water from the overflow release , and not from a cracked pipe or radiator.

I've uploaded the car picture & indicated the tank.

I don't understand the manual as I can't read tech German.

Attached Thumbnails

 

Any chance you can get some close-up shots ? It's likely that is the reservoir, but let's make sure.

Maybe a photo of the relevant handbook page would be useful?

Unable to get other close-ups right now.

If the cap is labelled "710" then don't put water in.

HTH

Ok, crisis over, my neighbour is a car mechanic & I've just caught him walking his dog, many thanks, much appreciated!