I just want to be be clear that this is where the clay based grease is to go on my disc brake (1998 U320) PIC BELOW.
That is the correct place and be sure to follow the instruction of relieving the pressure afterwards.
I am going to presume this is the procedure (as per all things foretravel)
Caution!! Do not use lithium-based grease inside the caliper. Lithium-based grease may not adequately lubricate the caliper. Damage to the caliper can result. Use only NLGI # 1 or #2 clay-based grease inside the caliper.
1. Turn the adjusting nut of the slack adjuster to move the inboard lining against the rotor.
2. Plug the pressure relief valve by holding a finger over the poppet.
CAUTION: You must force excess grease from the caliper. Brakes can drag from too much grease in the caliper, which will reduce brake lining life.
3. Apply grease through the grease fittings in the caliper until grease flows out of the seal at the power shaft cap.
4. Remove the pressure relief cap from the caliper. Turn the slack adjuster adjusting nut in the opposite direction to fully retract the caliper piston and force excess grease through the pressure relief hole.
5. Clean excess grease from outside the caliper with a rag.
6. Install the pressure relief valve.
7. Adjust the brake.
8. Install or re-engage the brake on the automatic slack adjuster.