Hey guys.

I just made it to Vault 19 on my way north. Went inside and found Lem first. I talked to him and I tried to seal the sulfur but not enough skills in explosives. So I trek back up and finally talk to Cooke instead. I never agreed to help him (I chose to go down to the caves before talking to him) and I already get an option to tell him I cleared out all the Geckos. I say "Yes," and then he asked me if I want to help him. Regardless of what I pick, immediately afterwards, I get a popup telling me I'm merciful for helping. I walked out into the hall and tried to go inside of Lem's room. The door was locked. All it said was that I needed a key to open it (not a blue or RED sector card). I immediately remembered that there was a path through underneath the overseer desk. I go inside and I see Lem's exploded corpse.

What happened? If you talk to Cooke about helping him (doesn't matter if I agree or just say goodbye to end the conversation), Lem explodes and the door locks?

How do you blow up the cave entrance?, i have C4 but cant find any place where it tells me to put it...if i just throw it in the hole nothing happens when it explodes??

No one that has done Vault 19 and can help out??

@ PhrodoLaggins
By clearing out the cave area and then reporting to Cooke without destroying vault 19, you are helping them to aquire the sulfar to make more explosives. As far as Lem going boom, idk! Maybe a bug or sumthin' from doing the quest backwards?

@Ceano
In order to destroy Vault 19, you need 4 or 5 blocks of C-4 and an explosive skill of +60 (maybe higher). Down inside the cave area there is a pile of sulfar that you have to attach the C-4 to by using the action button. Tossing the C-4 onto the ground won't do anything. Keep searching for that sulfar pile because it's there. It's a formation that looks unlike anything else in the cave.

I've had my own problems with this quest (not identical to your situation, but bad enough that I had to use the console to fix it).

If you're on the PC, I'd recommend using the console to reset the quest, resurrect and disable/re-enable Lem and do it over, not talking to Cooke this time just to be careful.

Is there a way to get Lem and the ones who want to turn themselves in to NCR out of the vault? I haven't seen an option. This is what I would like to do.

I don't have a 60 explosives skill and probably won’t for a long time, if ever. I found two of the c4 packs; I will look for the third for a while.

At one point Cook did ask me to go to the Khans (I went back a save at this time) and talk to them to let them join them. I don't think I want to do that. I could go talk to them and see what happens or I could just kill Cooke and everyone else. There is this one guy with really cool mirrored shades and a couple others with nice cowboy hats....the humanity


Seriously I really would like to help Lem turn himself in. BTW I went and killed Cooke and Lem turned red on me. I reloaded the save so I can go back in later

Any help? Thanks!

The Lem exploding thing seems related to raising the overseer's chair. Either there's a script that kills him when he tries to sit in the chair or the game just parses that automatically. The difference being in whether or not its intended.

Lot of confusion here.
There is a giant circular 'formation' in the cave, that you put explosives on. It looks like an enormous meteorite - you'll know when you see it.
You need to turn right and go uphill, as soon as you enter the cave, to get to it.
With 5 C4 and Explosives skill of 50, you can destroy the caves and vault.
With only 3 C4 but requiring an Explosives skill of 60, you can blow up only the caves.
This allows you to return to Lem and advise him to turn himself in...
I would have gone to visit the Khans (who idolize me) on his behalf, but I had already convinced them to break up with Caesar and abandon camp.
Dunno if the Khans were still there or what - so I just recommended Lem go to the NCR (it's what he wanted, heheh...)
Blowing up everything is not good, and fails both quests.
An explosives skill of 60 is easy, LoL.
You need only a skill of 40, plus a Patriot's Cookbook magazine...
(If the magazines give you only 10 buff, you're choosing different perks than I am.)
These guys have their own unique faction, 'Vault19 Powder Gangers', and they have their own slideshow in the ending montage.
The quests are mutually exclusive.
Whichever guy you go back to, the other guy blows up and his door locks.
No, TCL won't work, heheh...
Hope this helps,
Regards