The hydraulic cylinder is the most important part of a hydraulic system. Without it, the system simply can't function. It's also one of the most uncomplicated parts of the system, meaning that repairs usually can be conducted also by inexperienced people. The least you can do as someone who doesn't have any experience of hydraulic cylinder repair is to examine the cylinder to find a source to the problem you're experiencing with your hydraulic system. To do a proper examination of your hydraulic cylinder, there are a few things you should know to keep an eye out for. 

Piston seal

One of the first things you should check is the piston seal. This is an important part to examine as it can be an indicator of truly devastating issues with the hydraulic cylinder. Make sure the seal isn't discoloured or eroded. If this is the case, then you probably have a problem with the barrel in the hydraulic cylinder. It might be too large or has bulged during hydraulic cylinder service. In this case, simply changing the seal won't be enough to fix the problem. This is, therefore, a repair you shouldn't attempt to perform on your own if you don't have any prior experience, as changing a seal might be quite simple, but changing a barrel or the whole cylinder is rather complicated.

Rod seal

The rod seal is another seal that might indicate bigger problems if it doesn't look like it's supposed to. If the rod seal is broken or eroded, this is most likely an indicator that the rod has been bent or that the guide bush in the cylinder is damaged. This causes all the weight accumulated when the cylinder is operating to be put on the seal, which causes it to break or erode. Once again replacing the seal won't do anything to solve the actual problem and you need to have the cylinder looked at by a professional.

Rods

Another common issue with cylinders is bent cylinder rods. This is something that is usually examined by a professional by putting it in a roller when the hydraulic system is being repaired. However, spotting bent rods before they start causing extensive problems can save you both time and money. The easiest way to determine if a cylinder rod is bent is to look at the surface of the rod itself. If the chrome seems worn on one side by looking duller than the other side, this is a firm indicator that the rod is bent.