Strange Clicking noise in ps2......

[gtapex_trueno]

Hi, I have a v4 ps2 I believe with a messiah 2 mod. There's a strange clicking sound that came from my ps2. It got to the point where I started hitting the thing and for awhile it refused to play any games (Stayed at the floating icon screen with browser and the other option, didn't go into rsod...thank god) . In frustration I took apart the ps2 and went to check the laser. I fooled around a bit and out of curiousity and at the point of giving up, I took off the little black cover that is around the laser. I tried the system with that off and..... no more clicking! I put the ps2 back together and it started working!! But..... now it started clicking again and I'm ready to start taking it apart and fooling around with the laser once again. Anybody have anyt idea whats the matter with my ps2? When the ps2 was open, nothing moved (laser and all, the sound came from the laser I guess (inside the black little cover?) ) Any ideas? Any help is greatly appreciated! Thanks!