What is the purpose for the two round rubbers on my sentra radiator?

Sounds like a. Heater core leaking somewhere

Not sure which item you are talking about?? If you mean the blower for heat system it is under dash behind a cover. If you are talking about a radiator cooling fan it is behind radiator and requires removing a few bolts at top of radiator support - unplugging the wire to fan unit (push in tab on wire bundle and pull apart), and then lift fan unit up and out. You may have to remove plastic cover, and upper radiator hose to lift out, but fan is usually just held in at top by bolts and sits in rubber footings at bottom.

Open your hood. The EGR valve is attached to the metal emissions tube above the intake manifold and next to the firewall. It is a round, metal cylinder with a rubber vacuum hose running from the top of the valve.

Those are the rubber insulators that insulate the radiator from the metal part of the lower radiator support. They have nothing to do with the radiator leaking fluid. The fluis is likely coming from the tank seam on the side of the radiator and running down to that part. There is nothing you can service on the radiator. If its leaking the whole radiator will need to be replaced.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

is the car over heating? if not replace rad cap the old one might have a bad rubber seal.

check your radiator if theres a bubbles while your engine runnin, if theres bubble, it means you overheat. check your cylinder head for warps... also check your fans...

water pump belt,tire rubbing the plastic cover in fender whell,
wires laying on the exhast

ccarver96: 1st the radiator, unless it has been replaced with an aftermarket "all metal" radiator, is going to be aluminum with plastic tanks.
Your radiator should have large round pins about 2-3 inches long manufactured on the bottom plastic tank. You should have something similar on the top tank. These are out near the ends facing downward. for the bottom tank and straight up for the top tank. coming off the lower core support, there should be places with holes and there should be large rubber grommets which fit into the holes and then the pins for the radiator, fit inside the center of the grommets. This way you have rubber isolating the plastic from touching metal.
At the top, there will be brackets which will have rubber rings which fit inside the brackets and the rings fit over each pin on the top radiator tank. The brackets then are bolted to the upper tie bar of the core support. You now have a radiator which is secured within the body of the car but has rubber mounts which keep it from touching metal. That is what keeps the radiator from getting damaged.
If your radiator is getting damaged other than that, if it is touching the body at any other point, the body has been damaged and needs to be repaired.
If the radiator is being blown apart from running hot, you need to have the cooling system checked or give me more input as to where the radiator is splitting. Is it splitting at the seems from heat?

radiator fan or the heater fan????

Find the big hose that comes out of the top of the radiator and follow it to the engine and that is where the thermostat is located. My advice is to be sure to get a factory thermostat and rubber gasket as it makes installation much easier. I have done it both ways and the factory one is easier to install.