When a thrust reverser has been removed from the a/c, or when the hydraulic system has been opened due to a component replacement on the thrust reverser, it often happens that the reverser sleeve will not move during the first attempt. This is almost always the result of AIR, and nothing but AIR in the system. This is not stated in the AMM. The trust reverser is a “dead end” hydraulic system, which it makes it very difficult to bleed automatically. So do not replace actuators or sync-locks to quickly. Just try to bleed the system many times, by loosening the end-plug at the hydraulic lines in which the synchro-cables are running and toggling the hydraulic pump. It can make a skydroll mess on the floor, but for sure the sleeve will move again! Operate the reversers many times, allowing enough time in between. So the tip here is bleed, bleed and bleed again!
Another tip from Pat Paterson;
737 reverser will not stow after maintenance:
operate with standby pump on, this will clear the hyd lock.
> FOR INFORMATION ONLY. UNCONTROLLED DATA !.