So my S5 has (I believe) a power steering leak. There's liquid/oil/whatever all over the underside/toward the front Appears to becoming from the rack and pinion.

Quickly looking around I see a rebuild kit on Atkins for $220 USD but I also found remans on RockAuto and fleaBay for around the same price in CAD. To me, it seems like getting a reman is the route, both for ease of work and price. Is there another source for rebuild kits?

Thanks.

 

To me, a reman would be the route to go, but make certain it is the same rack as there are various
racks available for the S5.

 

That price is insane. Rockauto has a kit for $75 Canadian, which should be even less in USD:




Now that being said, I've purchased a kit 2 (3?) times, because I've never been able to get a rack rebuild correct. The first time I did it, there was user error on my part. That's on me. But the second (and third, maybe? Don't quite recall) time that I rebuilt it, I definitely made sure everything was right. It would work for a few months and then spring another leak.

I've documented the process in my build thread with tons of pictures, but I recommend you just do what I ended up doing and buying a reman.

 

I've read through various parts of your build thread but did not see the "rack and pinion rebuild saga" section - not saying much since I overlooked the rebuild kit on RockAuto too. I'll go back and look.

I thought so too. But thought I would check the 2025 consensus first. Good to know there is different ones. I guess that means a S4 would very likely not fit? My brother just got a S4 for parts, I was secretly hoping I could use that one.

 

No, they're different. The geometry is the same and the column has the same splines (I think), but the S4 rack has three ports for fluid and the S5 has the more common two port arrangement seen on most racks. This means the pumps and computers are also different. The ratio for S4 racks is 15.4:1, S5 is 17:1, so the S4 rack is a significantly quicker ratio.

You could technically swap them, but any swap would also require swapping the lines, pump, computer, and very possibly making changes to the wiring harness. The S4 computer also senses wheel-speed as well as engine-speed, but the S5 rack only senses engine-speed (I think), meaning some necessary wires might not even be at the plug for the computer.

 

The S5 came with two different PS systems depending on model. The TII and GTUs models had vehicle speed sensing (VSS) PS, and all other models had engine speed sensing (ESS) PS. My '90 GXL has ESS PS.

IIRC, ESS PS has 2 lines and VSS PS has 3 lines.

IDK about compatibility between S4 and S5 PS systems.

Check your hoses at the rack. I once had a leak suspecting it was the rack but it turned out to be a hose.

 

That's interesting - does this mean there are 3 line S5 racks with the 17:1 ratio? I've never seen one but that doesn't mean they don't exist.

The third line is for something that I've never seen on any other car other than the S4 FC (or possibly S5 if there are indeed 3 line S5 racks). Mazda calls it a "reaction force" tube. I'm a little hazy on the mechanics of it, but basically this third line incorporates the resistance of the wheel turning against the road into the assist level. This extra line combines with something in the pinion to dynamically decrease assist depending on grip. The end result is that on snowy roads or in rainy conditions, where the rubber is not experiencing as much friction against the asphalt as normal, this tube decreases the amount of assist as you turn the wheel to increase steering feel and prevent twitchiness

I can't say I've ever noticed it doing anything. That either means it doesn't work, or it works so well that I don't even notice it's there. I will say that (when it's working properly) the 3 line S4 rack is my favourite steering rack that I've ever used on any car, FC or otherwise. I'm probably biased since my FC was my first car, but a few cars later (and having driven many others) it remains my favourite.

 

TII has has VSS PS (3 line rack). Checkout this link: https://www.importapart.com/product/...mbly-oem-3212/

IDK about the ratio. I out of town for the holidays, so I don't have access to all my resources.

 

Thanks for all these details. This is getting interesting. My car is an NA to TII swap. So it would be interesting to see if they swapped the steering rack too. I'll have to check it out and take some notes.

 

There are 3 Steering racks for a LHD FC. There is/was a stick on the rack so ID is really easy.
The Manual rack is FB01, its found in S4's ratio is 21:1 or something like that, ie really slow.
The 3 line rack, is FB05 or FB78, its all of the S4's with PS, and the S5's with 3 lines. its the fastest, 15:1
the 2 line rack, FC01 is in some of the base model S5's, this one is 17:1, so its a little slower. starting in 1990 you start to see it on the lower models

 

That's really helpful. Thank you. I also just went back and read WondrousBread's "A Series of Less Than Logical Choices: An S4 Build Thread" to read through the PS rebuild portion. All good info.

Car is jacked up in the garage while I'm tinkering with wiring (I decided it was easier to get at what I was working on). So I'm going to inspect sometime this week what's there and as noted, look for loose connections. Probably wouldn't be a bad idea to clean up the whole area and try to determine where my leak is actually coming from. Priorities, and the list is long.