There should be a positive post under a red shield in the engine compartment. Connect the positive side first on the vehicle to be jumped, then connect the negative side cable to a good unpainted bolt on the engine or one supplied on the body near the positive jump point. Then connect the other end of positive to a good battery of higher capacity than what your car has. Last connect the other end of the negative side cable to a good unpainted bolt on the engine or one supplied on the body. Start the engine on the good car battery and let run for 5-10min. to charge the low battery as much as possible, then start the car to be jumped.
The CLK uses a C209 body shape. Its also a 2 door. The CLS uses a C219 body shape and is a 4 door.
The EPA mileage estimate for the 2013 Mercedes-Benz M-Class is 18 mpg in the city, 23 mpg on the highway.
Is it water or anti-freeze? If its anti-freeze your heater core is leaking which is usually a costly repair.
If its water its probably a problem with the body drain. Seems to be a on going problem with some Mercedes models even S class.
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Is the water leaking from the passenger's side? If so, the water would most probably be coming from the heat blower motor area, it is under the gloves compartment. This usually happens when the drainage pipes (under the hood in front of the windshield) get clogged by tree leaves, and rain starts to build up on them. It is a common problem in Benz cars.
If the CL you are referencing is a 98 or 99 - which in Mercedes factory speak makes it a 140 chassis, the trunk was designed to be opened by remote control fob. There is a strong spring which will open the trunk completely once the lock is triggered, either manually on the trunk, or by the remote key fob.
If you mean the trunk is only opening half way, the spring can be broken, or it may not be fastened tightly on the hinge, but you should be able to easily open the trunk the rest of the way by hand.
If the "soft-closure" mechanism is not working property, it can be reset by taking both fuses out that are identified as to that system for 15 seconds, which will allow the computer to reset. It should begin working again unless the system has failed completely, and then there is a central Bosch system box that needs to be replaced.