What size Allen wrench do I need to remove the front calipers on a Mercedes ML350?

Allen wrenches usually come in a set, try 3/8.

I'm not sure of the size. I have an allen socket made for GM brake calipers!! But i would guess it is a metric size, maybe a 12 mm. Call an auto parts store and they can pull the tool and tell you with a phone call. Good luck.

Allen wrench size to remove brake caliper on my 2008 mercury mariner

i just changed my front rotors and pads on my 2001 escape, 6 cylinder. everyone was wrong on the wrench sizes, including the idiots at my local ford dealer. to get the brake calipers off I needed a 7mm hex bit. to get the caliper bracket off I needed an 18mm socket, it was a very easy job but check your wrench sizes first, it seems that every year and model uses different sizes.

Hi, welcome to FixYa.com my name is Shawn and I will be answering your question.

It is a metric 9 allen wrench or allen socket.

I hope my assistance helped you and resolved your concern, if you need further assistance please ask.

First, you you managed to give the year, but you forgot to mention MAKE and MODEL...Nice-to-know ...especially since you are asking for SPECIFIC information that does not apply to all vehicles.
Second, I have no idea what a "star" tool is unless you are refering to a "Torx" driver.
Third, MOST GM vehicles built in this century require neither an Allen wrench or a Torx driver. Most calipers can be removed with either a 15mm or a 13mm socket or wrench.
I would recommend removing the tire and wheel assembly to LOOK at the caliper and see what is holding it.

You will need a 7mm allen to remove the front brake caliper.

i just changed my front rotors and pads on my 2001 escape, 6 cylinder. everyone was wrong on the wrench sizes, including the idiots at my local ford dealer. to get the brake calipers off I needed a 7mm hex bit. to get the caliper bracket off I needed an 18mm socket, it was a very easy job but check your wrench sizes first, it seems that every year and model uses different sizes.

it is a 3/8 allen wrench

So this is what it takes to replace rear brake rotors on a 2003 Mercedes E320;
1) open the bonnet (hood) of the car and loosen/remove the cap off of the brake fluid resevior.
2) remove outer spring clamp from brake assembly (it clips in to the iner edge of the holes of the caliper).
3)using a 7 MM allen wrench, remove the brake caliper.
4) using 18 MM box wrench, remove the caliper housing assembly off of the wheel hub.
5) using a star wrench, unscrew the rotor locking screw from the rotor
6) squirt some liquid wrench on the rotor hub and knock the rotor with a hammer to work the liquid wrench in.
7) using the same hammer, knock the rotor off the hub.
8) using a metal file, lightly file old residue off of the hub and place the new rotor on the hub.
9) set the hub by screwing in the lug nuts and then screw in the hub locking screw using the star wrench, then remove the lug nuts.
10) reinstall the caliper housing assembly onto the wheel hub using the 18 MM box wrench.
11) push back the brake claiper piston to its home position and install the inner brake pad (the one with the snap clips)
12) insert the outer brake pad in the claper housing assembly.
13) slide on the caliper housing with the inner brake pad in place (over the outer brake pad) and screw in the caliper screw rods using the 7 MM allen wrench
14) on the right wheel brakes, DO NOT FORGET to slide in the brake sensor (the one with the black connector) and connect it to the connector on the caliper housing.
15) be sure to reinsert the spring clamp onto the outer brake assembly to set the assembly squarely onto the wheel (there should be no wiggle in the brake assembly after the spring clamps are installed).
16) finally mount the wheels.
17) you can bleed the brakes at this point to release any trapped air (which is unlikely) but be sure to pump the brakes after starting the car BUT BEFORE MOVING IT to re-preassurize the brake system before driving the car.
17) ONE WEEK LATER - recheck brake assembly to ensure all is okay and brake fluid.

This proposed solution is for a 2003 Mercedes Benz E320 and NOT a 2005 model as stated by the limited option selection provided by FIXYA.com when initially describing the problem.