The high-pressure power steering lines are known to leak.
Car Problem Reports
Cadillac Seville STS High Pressure Power Steering Hose Can Leak Fluid
Cadillac Seville STS Problem
Average Mileage: 124,855 mi (71,000 mi - 200,000 mi)
Visitor, 1994 Cadillac Seville STS, 103,565 mi
Had a leak in the high presure side of the power streering, was leaking and the Dealer said the line had to be changed at $200.00 plus for the part and labor. Took it to a regular shop that I use. He got what he needed at NAPA for $60.00 and I got it fixed for a little over $100.00. I have found that most of the issues can be fixed by regular Auto repair shops.
Visitor, 1994 Cadillac Seville STS, 200,000 mi
My car all of a sudden had no power steering, and after verifying that the pump still seemed to work, I'm assuming that the hose is bad as well. I really don't know though and am still looking. Powersteering makes a really loud noise when I turn the wheel and the car is not keeping the power steering fluid.
Visitor, 1999 Cadillac Seville STS, 71,000 mi
Experiencing this issue now, replacing the line soon.