Truck Repair: Sterring problem on 1998 GMC, pressure relief valve, gmc 1500

Question
Hi Van I have a 1998 GMC 1500 4x4 when I am traveling I sometimes feel the steering wheel free up for a split second. It's not like it is pulling but like the power steering all of a sudden decided to work harder. It doesn't happen all the time in fact one day it will be fine and the next it may happen several times. This has been happening for almost a year.Could a slipping serpentine belt cause this? Power sterring fluid is fine and no apparent leaks.     Any Ideas?  Thanks

Answer
Hello Davis,
Could possibly be the belt slipping, but I am surprised you can't hear it if it is.
If you have the hydroboost brakes operated by the same pump and fluid, there could be a valve sticking in it, but I don't think a 1500 had that system...it is on heavier trucks.
The pressure relief valve in the pump could be sticking open, and just closing occasionally. A pressure test would be needed to confirm that.

Van