Originally Posted by OffroadFrance

Purely a guess without seeing/testing as it could be many things but, I guess it's an air in the system problem or the hoses need replacing or both. However, it could also be brake pad push back on the caliper(s) due to slack wheel bearing(s). Another possibility is the vacuum line to the brake servo is leaking or even the servo defective. Lastly it could be the master cylinder seals defective. It's a process of logical elimination I'm afraid.