Surasonac

My old engine mounts were collapsed so I bought some refurbished mounts which had been filled with polyurethane.
I installed them yesterday and they feel awesome. However the top bolt on the left side appears to have snapped inside the mount and just spins and won't tighten, I can't back it out either.
It seems to be holding as it won't come out but I need to replace it.

I am ordering two new M10, 1.25 pitch, 30mm length bolts. Obviously that engine mount is fucked now, so I need to convert my old engine mounts to polyurethane so I can replace the one with the wrecked bolt.

I have cut the rubber bits of the bottom of the mounts and oil came out, however no more oil seems to be coming out. I shake it and hear oil inside, but I've tried rotating it around in my hand and shaking it vigorously only getting small spurts of oil come out at a time. I just can't seem to get it all out.

Does anyone know a trick to getting the remaining oil out? Is there a valve in there or something?