Buying your own parts is a real bad idea unless the people at the repair shop ask you to do so. That only applies when the part is rare or hard to find and will take up a lot of their time and resources. Supplying your own parts is like bringing your own food to a restaurant and asking them to cook it for you. If you don't like the quality, the cook is off the hook and you have to bring some more food.
When the repair shop supplies the parts, they make a profit on them, just like every other store, but then they assume the responsibility if one of them is defective, if it's wrong, or even if they accidentally break it. They have to get someone to order it and get it to the shop. That profit also goes to pay the mechanic to do the job a second time when the reason is not his fault. In this case, the dealer can expect you to pay for the labor a second time since they didn't supply the part.
That said, I'd have to see the leakage for myself, but my suspicion is there are o-ring seals on the two steel lines that didn't get replaced. Depending on the design, the leaking fluid can build up in a cavity in the frame or cross member, and it has to build up high enough before it runs over and causes a leak on the ground that you can see. Those o-rings almost always come with the replacement steering gear, but they're in a plastic bag and have to be placed on the lines by the mechanic.
There could also be a hairline crack on the end of one of the lines. If that migrates high enough, it will spread past the o-ring to where the fluid will leak out by the threads.
There is very little that can go wrong with a rack and pinion steering gear, and you'll always buy a rebuilt assembly. You only get a new one when the vehicle is under warranty and the manufacturer is supplying it. I've never run into a problem with a replacement rack and pinion assembly, so that adds to my suspicion that something else is being missed or overlooked. I would approach this by washing the area with engine degreaser, then running the engine with the vehicle on a hoist to see exactly where the fluid is coming from. Even a real slow leak should show up as wetness that is visible after a few minutes. You may have to work the steering wheel a little as that will increase the pressure in the supply line.
The steering gear can only leak from two places if a seal fails. One is at the input shaft, and that usually results in power steering fluid running onto the carpet by your feet. The other is past either rack seal. That's by far the most common failure. The fluid will run into the accordion boot on that side, build up over time, then run through the small equalizing tube to the other boot. There's a 50 percent chance it will eventually run out on the left side, regardless which seal is leaking, the left or right one. If the fluid is leaking from where the hoses attach, there could be a tiny crack through the threads, but that is real uncommon to run into on one steering gear, and real unlikely to occur with two or three of them. A cut o-ring seal is much more likely.
Wednesday, December 9th, 2015 AT 6:15 PM