What would cause a grease gun to lock up? Our maintenance department is having issues. While we are greasing bearings, the gun stops pumping half way through the tube. Is this the gun, the grease, or both? Is it an industry wide problem?

Sounds like an air pocket to me. There should be a little relief valve at the top of the gun. Just hold it down while you pump,and try to purge the air out until the grease flows. If there is no valve, uscrew the gun top part way, and do the same thing until grease flows, then screw it back on. If this doesn't work, just try a new gun, as they are not expensive.

What do you mean by lock up? Does the gun stop pumping grease but you can still freely pump the handle? If that is the case air pockets are likely the culpret and the previous advice applies. If your grease gun hydraulicly locks and you cannot pump the handle then you may have something blocking the discharge of grease from the gun. A faulty check valve, some foreign material in the hose or nozzle or something else. As was previously mentioned a new grease gun is a fairly modest investment but get one from a major manufacturer such as Lincoln or Alemite the cheap foreign ones are just that.

Thanks for the info. The guns we use have instructions describe how to purge the air. Most of our guys knew about this but some of the new guys didn't know or don't have the patience to stop and think to purge the gun and want to blame the grease.