2002 gmc envoy

When I press the brake pedal there is a crunching sound from the front. Sounds like it is coming from the left side. Had a mechanic look at it and they said brake pads needed to be lubed where they slide. The crunching sound is still there every time we use the brakes. I personally checked both sides and all seems fine. Could this be the caliper making this sound? Any suggestions would be appreciated. Trying to avoid taking it to the dealer as they are very expensive, always find something else to charge us for. Thank you very much.