Greetings!
GM racks had a lot of problems in the 1980's/ early 90's with internal seal leakage when the racks were cold (the moring sickness you mention). the seal materials used would contract when cold, allowing fluid to bypass them; after the fluid warms up they seal better.
Often seal conditioner additives that soften rubber help with the morning sickness issue; there are many of them on the market, available at parts stores.
The fluid overflowing the cap is probably either due to the fluid blevel being overfull (fluid expands when it gets hot), or too low (if the fluid level is very low, the pump will cavitate (suck air and beat it into the fluid) causing the fluid to foam.
If the fluid overflowing the reservoir appears clear and not foamy, then it is most likely just overfilled. Pump faults do not usually cause fluid overflow.
If pump performance is suspect, most repair shops can verify pump operation by measuring the pressure at the pump with a special pressure gauge set.
I hope this is helpful; if so, please click my accept button! Thanks!
