Silicone Not Curing
 

I have twice torn into my Prius to repair a water leak at the joint of the firewall and front end. The previous time I just missed a section of the seam and water was still infiltrating the cabin.

This time, I hit the seam well with silicone sealant, and after the downpour today, not a drop of water made it inside.

The problem is that the sealant was way expired, and is failing to cure. A day later, it's nearly the same consistency as when I applied it.

I don't think I could clean it out and reapply new stuff due to how difficult it is to get to. I had to use a straw to apply it in an impossible spot to get to.

Any suggestions? Should I just put everything back together and hope it doesn't spring another leak? My fear is that once I hit the highway, air pressure will create a hole in the goop.

Old RTV doesn't cure, just stays mush.

If it is like window caulking or clear silicone, I have had it take several days to sure. Think about how long it takes to cure in the tip of the tube. Will take longer if it typically stays wet.

I'm still hoping it will firm up as it was applied in low 40s temperatures, and then it rained shortly after that.

It seemed to begin curing a half an hour after applying as it did clump a little when spread, but last night it felt about as soft as it came out. I was hoping there might be a spray curing agent I could hit it with since I don't think I can remove it.

Perhaps it's just thick enough to hold up to whatever air pressure the firewall is exposed to and the repair will last. I'll take the car on the highway in the next couple days and see if the repair holds. If it does, I'll put the interior back together and stop worrying about it until/unless condensation begins showing up again.

I'm reading online reports of some environmentally friendly silicone that expires soft instead of expiring hard. I didn't think that was possible, which is why I figured if it was soft, it was good.

When it is cold it takes forever to cure.
I repaired a partly rotten window and primed it when it was about 15 degrees Celsius.
Temps went down to 5 overnight and back up to 12 the next days. It was still tacky one week in.
It should have been dry enough for sanding within a day at 20 degrees...

The rot filler compound should have cured within 3 minutes. Thankfully it took longer. Sadly I had to push it back into shape every our or so for the rest of the evening. But I could sand it the next day.

Compound filler and paint aint silicone - but I'd give it lots of time if it stays cold like that.

Check with your local distributor/sales rep...he might know WHAT stuff you could use as a "catalyzer" to *force* the silicone to harden.

Good idea about talking to someone about a catalyst.

I think I have sufficient room to work from the inside near the kick panel to clean out the goop applied there and then apply a fresh bead of polyurethane. I'll leave the outside silicone alone since I can't reach it, but perhaps sealing from inside is sufficient.