Cracked neck - anyway to prevent it from spreading?

[98dvl]

I recently picked up a t-40 that's in great condition - except there were some issues with the neck. When I picked it up, there was quite a bit of relief in the neck with the strings taught. The previous owner said that the truss rod was maxed out, so she was selling it for cheap.

I brought it home, and inspected it further... I noticed a small (about 3/8" long) crack on the back side of the neck, about where the pocket for the truss rod nut ends... I took off the truss-rod cover and sure enough, the nut was bottomed out on the threads on the rod. I took the nut off, added a few washers, and was able to straighten the neck out a bit more...

However, now I've noticed that the neck has also developed a crack on the finger board side (the neck is a two piece maple neck... it looks like the two halves were glued together). The crack is right at the top of the nut, and spreads down to about 1/4 way to the first fret - again right where the truss rod nut pocket bottoms out at. The crack is right in the middle of the two halves of the neck that are joined together.

I may mention that when there was no tension from the strings, the neck was rather straight (no back bowing)... With the tension in the strings, it was barely playable because the action was so high. So, I believe this to be the reason why it really took the extra washers to get it (somewhat) straight. It's not as straight as I'd like it, but it's MUCH straighter than it was before, and with the crack, I'm not going to push it any further. (Probably another 1/8 to 1/4 turn on the nut will get it where I'd like it).

I'm worried that the crack may propagate down the length of the neck... especially if the bass gets knocked over or something.

Is there anything I can do to keep this from happening? I have a feeling that the truss rod is putting a lot of stress on the joint of the neck. I was thinking super glue (or something) might keep it from spreading, but wanted to get some advice before I try that.... I can post pictures if it would help.