Schwitzer S2A Turbocharger Overhaul and Repair Instructions

Schwitzer S2A Turbocharger Overhaul & Maintenance Guide

This data sheet covers the recommended engineering procedures for dismantling, inspecting, and overhauling Model S2A Schwitzer Turbochargers. The repair must be carried out using an original Schwitzer Overhaul Kit. To ensure long-term reliability and proper operation, all limits and assembly guidelines must be strictly followed.

1. Required Tools and Chemical Compounds

To service the Model S2A turbocharger correctly, the following specific tools are required:

Circlip pliers (snap ring pliers).
12-point sockets: 3/8", 1/2", 5/8" A/F (actual socket size depends on the specific turbocharger model size).
Torque wrench: 0-15 lb. ft. (0-2 Kg. m).
Open-ended spanners: 1 1/8 inch and 10 mm.
Insert extractor tool.
Compounds: Loctite 290 threadlocker and a high-temperature anti-seize compound such as Fel-Pro C5A.

2. Dismantling Procedure

Before beginning disassembly, always mark the relative positions of the compressor cover, the turbine housing, and the bearing housing to ensure correct alignment during reassembly.

Fix the turbine housing in a vice using soft jaws with the turbocharger shaft facing vertically.
Remove the large circlip securing the compressor cover. Remove the V-clamp securing the turbine housing and lift the central core assembly (CHRA) out.
Clamp the appropriate 12-point socket wrench in the vice. Place the 12-point hub of the turbine wheel into the socket. Release the compressor wheel locknut. Note: Later models use a left-hand thread!
Remove the compressor wheel. Gently tap the compressor end of the shaft with a soft-faced mallet to remove the turbine shaft from the bearing housing.
Using circlip pliers and screwdrivers, remove the insert assembly, thrust bearing, thrust collar, journal bearings, and inner circlips from the bearing housing.

3. Cleaning and Inspection of Parts

Aluminum Parts: Soak in a non-caustic solvent. Vapour blasting may be used, provided that all bearing surfaces are strictly protected.
Shaft and Wheel Assembly: Soak in solvent to remove oily residue. When vapour blasting the wheel and hub, the entire shaft section must be masked. Avoid concentrating on the piston ring seal groove. The shaft must be checked for eccentricity, and the whole assembly must be balanced in both planes.
Housings: Inspect the turbine housing visually for overtemperature damage (cracking, warping, or erosion). Inspect the compressor cover for contour scuffing.

4. Assembly Instructions

All parts must be washed in clean solvent and dried with compressed air. Only use parts that comply with dimensional limits, plus the components from the Overhaul Kit.
Fit the inboard snap rings to the bearing housing. Lubricate the bore and fit the journal bearings and outboard snap rings.
Fit a new piston ring seal to the turbine shaft. Fit the turbine backplate, lubricate the shaft generously, and insert it into the bearing housing, taking care not to damage the piston ring.
Fit the thrust ring, thrust bearing, thrust collar, and oil deflector.
Assemble the compressor-side insert assembly with a new O-ring and piston ring. Secure it in the bearing housing with the snap ring, ensuring the bevelled edge is uppermost.
Fit the compressor wheel and locknut. Apply 2 drops of Loctite 290 to the threads and tighten to the specified torque.

5. Reinstallation and Important Safeguards

No Jointing Compounds: Use new, approved gaskets at all air, oil, and exhaust connections. Do not use sealing compounds or liquid silicone at flanged oil connections.
Thread Protection: Use a high-temperature anti-seize compound (such as Fel-Pro C5A) on all threaded fasteners connected to the hot side of the turbocharger.
Drain Port Tilt Limit: Limit the oil drain port tilt to a maximum of 20 degrees from bottom center in either direction. Tilting beyond this limit creates a low-idle oil leakage tendency at both the turbine and compressor seals.
Pre-Lubrication: Fill the oil inlet port to overflowing with clean engine oil before connecting the feed hose. Before connecting the drain hose, crank the engine without firing until a steady stream of oil flows from the drain port.
Filtration & Operation: Oil filtration should be 10 micron maximum. Always warm up the engine for 2-5 minutes to allow oil to fully circulate before operating under load.

During Schwitzer S2A major overhaul the original Overhaul Kit (e.g., 318377 or 1261-988-0003) must be used and the thrust collar inspected for zero surface disturbance or scoring on the thrust face per the S Range Service Limits and Torque Values data sheet; thrust collar thickness and thrust bearing contact area are measured with a micrometer, any scoring exceeding 0.001 in. demands full replacement as it causes axial shaft play (TIR) beyond the 0.006 in. limit verified with a dial indicator mounted on the compressor flange. The journal bearing (part no. 194914 STD or 8-C-1247) radial clearance after installation must remain 0.002–0.004 in. – OD/ID micrometer check ensures floating bushing contact without dry friction even after applying Loctite 290 to the compressor wheel nut (left-hand thread on later models). Compressor wheel locknut torquing follows the “Pure Torque” or “Snug + Angle” method from official Schwitzer torque tables – after 2 drops of Loctite 290 on the threads the specified torque is 12–15 lb.ft (0–2 Kg.m) with a calibrated torque wrench, followed by light rubber-mallet tapping on the V-clamp (P/N 148313) to seat it evenly against the turbine housing; the snap ring for the compressor-side insert assembly is installed with the bevelled edge uppermost, and the thrust bearing plus oil deflector fitted only after shaft insertion into the bearing housing while protecting the piston ring seal groove – maximum groove width 0.068 in., otherwise idle oil leakage occurs. After CHRA reinstallation strict drain port tilt control is mandatory – maximum 20° deviation from bottom centre in either direction measured with a protractor, as excess angle creates low-idle leakage through both turbine and compressor seals due to impaired oil return; Fel-Pro C5A (or equivalent) must coat all hot-side bolts and threads, oil filtration must not exceed 10 microns, and before start-up the engine is cranked without ignition until a steady oil stream exits the drain port, ensuring complete lubrication of the thrust collar and journal surfaces prior to any load application.

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