Originally Posted by RV Captain
I need to check on the manufacturer of the slides system. There is no visible rails or pistons to lubricate. Some of the hydraulic hoses for this slide are under the bed beneath a wood board that covers the bottom of the lift-up bed storage compartment. I will check these hoses the next time I am at the RV. It's possible they are leaking under the bed..and that would be a mess!
I'd suspect you would see a change in the hydraulic fluid level in the tank.
Consider doing this: Extend the slide and then immediately put a piece of masking tape on the hydraulic tank to mark the top of the fluid level.
Let the slide do its thing a few times. If it's an external leak you should see a steady gradual drop in the fluid level when the slide is extended for the last time.
If it's an internal leak, I doubt you'll see the hydraulic fluid level change. The fluid leaking from the extend side to the retract side will not make it back to the tank and as soon as you extend the slide, that extra fluid will be used to help extend the slide.
You also could place a piece of masking tape at the level when the slides are fully in and try it that way.