Access and lubricate the o-ring that seals the upper push rod tube to the lower push rod tube. Sometimes when these o-rings are to dry they don't allow the push rod tubes to slide and keep pressure on the upper and lower push rod o-rings as the motor expands because of temperature. Hope this helps you. It worked for me. Let me know if you have any luck.
Remove the retainer, collapse the tube and look at them. Sometimes repositioning them seals them. See if the one that goes in the head is black or yellow. The yellow ones are pretty good, the black ones have a way of getting hard when the heads get a little too hot.