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I'm soliciting ideas on how one removes this piston from the bare PS rack. I've resealed enough racks but what makes this one different is the toothed track has a significantly larger OD than the rack bar itself, making replacement of the interior tube seal impossible without first removing the pressure chamber separation piston. This is a ZF7852 servotronic unit. ZF's documentation I've researched does not show this particular piston. I expected that two snap rings secure the piston in place and one is obvious facing the track end. The other is apparently shielded by the machined tapered portion of the piston. This is probably a no-brainer for a factory rebuilder but out of respect for the product there will be no hammering, prying, or torching today. Would appreciate any constructive input. Anyone out there already seen and overcome this snag? Toothed track OD oversize, seals must come off opposite end Hidden snap ring??? One snap ring obvious
If you post all the vehicle info including the VIN I will look in Mercedes WIS which is a digital service manual. Dunno if it'll have info about the internals of the R&P or if it'll just say replace R&P.
Thank you for the offer. MB has never supported detailed in-house teardown/reconditioning instructions of steering racks in the Workshop Information System. I can't blame their liability department...too much risk I would think. Regardless of the reasons, there is nothing to be found in WIS for my 211.182. Thanks again.
The hidden snap ring is under the piston’s tapered lip. You need a thin, strong hook tool or a modified pick to reach in and pull it out. Once that ring is out, the piston should slide off. Try soaking it with penetrating fluid first sometimes they’re stuck with varnish. No hammering needed.
RE: 2114602400 rack 211.082 modelAnswer from a 100% USA in-house remanufacturer. "On this2114602400 rack, this piston is hydraulically crimped in place at the taper after being located against the forward snap ring. A new tube seal and ring requires machining the piston and subsequent replacement with specialized tooling." All because the toothed track OD exceeds the ID of the seals. My rack seal and ring are being reused.
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