water leak coming from wiring harness

Its been raining for the past week on and off and my drivers side floor is wet. I've delt with this before and thought I had fixed it. Well one more spot to go. I know for a fact the water is leaking from where the wiring harness goes into the firewall. My question is how can I disconnect the harness to replace the seal? I know there are two screws holding it from the inside, but last time I messed with it I couldn't get it apart. Any tips/tricks/advice would be great. Thanks.

I will put silicone on after to be extra safe. But, I can't apply it to all for sides of the harness because its wedged between the wheel well and master cylinder, I really need to just remove the whole thing. Last time I removed both screws to get it disconnected from the firewall, but it seems there are clips or something holding it in? Any ideas?

I messed with it and finally got it apart. On engine side of the firewall there is a bolt in between the two wiring harness bundles that go into the cab, which I couldn't see. Now that I got both sides apart I could put a nice silicone bead around the slot for the harness. I put the harness back together on the firewall, did the hose test, and no more leaks.

Just go to the parts store and pick up a tube of "dielectric greas"e and apply to all the pins and then reassemble. It is the time tested way to keep moisture from messing with multi-pin connectors and shorting them to each other. Hate when the blue smoke comes of out stuff.

Dielectric grease it actually a non-condutive silicone which keep the weather out. With the connector clean the pins will touch each other, the dielectric just fills in the spaces between the pins.

Also I can not fully picture if the water coming into the vehicle or leaving the vehicle. You may be just fixing a symptom not the problem by reworking this connector..