Hi I have a 95 850 which recently I've has been having random steering problems. Two weeks ago I noticed that at certain points of a turn my steering felt tough and on occasion the entire turn (left and right). I went and flushed the Mobil Synthetic out of my P/S pump and replaced it with fresh stuff. Same problem, but randomly 2 days later the problem disappeared. In fact 2 days into the steering going back to normal I took it to my mechanic to install new outer tie rods (the boots were ripped) and a wheel alignment I've needed for several years. I asked him to check the system and he said everything looked fine and were tight. In fact the outer tie rods had no play, but since the boot was ripped it would be best to replace. A week goes by and then randomly one day it starts again. I hear the PS pump when I go into full lock. If I open the PS filler top I can see some flow when the car is on. I thought previously that if I try to open the PS pump filler top while it was running it should go all over the place. Is that true? There are no leaks in the system. I was searching the board and someone mentioned a u joint under the car above the rack that may need lub? Any recommendations or ideas?

Regards
Sandro