I have a 2011 make Maruti Suzuki Ritz LDi (Diesel). I'm attaching a photograph of the engine bay here. Where is the radiator cap located in this picture? How to measure the coolant level? Also, what are the caps in the circles?
The radiator cap to top up the coolant is just to the right of the battery.
The item in a red circle top left is not a cap but a braking valve (most likely) or abs unit (possibly) - either way don’t try and remove it : it is not just a “cap”.
The item in red at the bottom is one of the A/C charging or access ports - do not open it unless you have the equipment - I have not looked for the other port, but it will be there.
Edit based on comment: the connection to the radiator - bottom right of the image is so close to the top of the radiator that a separate filling cap is not necessary - but it may cause a slower filling time, but that will depend on where the other pipe from the expansion tank goes and its size so it may not be an issue at all.
WARNING: cooling systems are pressurised when hot, make sure it is cold before removing caps or undoing pipes.