How the EBPV Works on a 7.3L Power Stroke
The exhaust backpressure valve is a simple butterfly type valve assembly mounted to the outlet of the turbine housing. Its function is to simulate an engine load following a cold start so that the engine will reach operating temperature quicker. The position of the valve is controlled by the EBPV actuator; a cylinder and piston assembly cast into the turbocharger pedestal. The position of the actuator is controlled by engine oil pressure. The flow of engine oil to the actuator is managed by the EBPV solenoid (also referred to as EBPV regulator), which is threaded into the turbocharger pedestal directly behind the compressor housing and just in front of the EBPV actuator cylinder.
Rebuilding the EBPV pedestal refers to disassembling and cleaning the pedestal in addition to replacing the actuator piston and various related seals. The primary reason for rebuilding the system is that a leak has been detected, although we highly advise rebuilding this component if/when the turbocharger is removed for an overhaul. Turbocharger removal on the "OBS" F-Series trucks is relatively difficult and burdensome (comparatively), thus it is time and cost effective to address this system preemptively. Likewise, it is convenient to rebuild/overhaul the turbocharger if it is being removed to address a leaking EBPV actuator/solenoid. Kill two birds with one stone and rebuild everything at once. For more information on rebuilding a turbocharger, see: 7.3L Power Stroke TP38 turbocharger rebuild guide
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• Remove the turbocharger. See: 1994 - 1999 7.3L Power Stroke turbo removal procedures
• With the turbocharger and pedestal assembly on a workbench, remove the retaining bolt holding the EBPV solenoid connector to the compressor housing (10 mm socket).
• Remove the turbocharger from the pedestal (10 mm socket, 4 bolts). Discard the two o-rings between the pedestal and turbocharger, they are not to be reused. Set the turbocharger aside.
• Using a 16 mm socket, remove the bolt on the top of the EBPV solenoid, then remove the outer part of the solenoid by sliding it up the shaft.
• Remove the inner part of the solenoid by pulling straight upwards. It is generally extremely tight; the o-rings tend to swell and/or harden.
• Remove the snap ring on the EBPV actuator, then force the piston assembly out by gently tapping the actuator rod into the cylinder. Discard the piston, snap ring, and end cap; they are all replaced in the rebuild kit.
• Examine the bore of the actuator cylinder with a finger. If there are any imperfections or buildup the cylinder needs to be honed.
• Hone the cylinder using a brake cylinder hone and LIGHT pressure. There's no need to remove a lot of material, but a smooth bore free of any imperfections and buildup is desirable to ensure a positive seal of the new piston. Dip the hone in clean motor oil frequently during this process. Check the condition of the bore with your finger - once it is smooth and free of any buildup, nicks, etc, stop honing.
• As an optional step, you can polish the bore of the EBPV actuator. Honing the cylinder can theoretically leave deep scratches (for all intents and purposes) and polishing it may provide an improved, longer lasting seal. We used a 3 step process (3 different polishing abrasives) from a standard aluminum polishing kit. The result was an extremely smooth cylinder with a light crosshatch from the honing process. As stated, this step is entirely optional.
• Thoroughly clean the actuator bore and all orifices with a solvent (brake cleaner, etc) before continuing.
• The EBPV rebuild kit from Garrett includes a new piston assembly, cylinder end cap, end cap o-ring, end cap snap ring, and o-rings for both the pedestal-to-turbocharger and pedestal-to-engine block mounting surfaces.
• Remove the EBPV actuator disconnect clip/latch (connects the actuator rod to the EBPV) by unscrewing it from the rod.
• Liberally coat the actuator piston AND actuator bore in clean motor oil, then install the piston into the bore until it is fully seated.
• Install the cylinder cap o-ring (coat in clean motor oil), then the cylinder cap itself over the bore and secure it with the new snap ring. Ensure that the cap is fully seated before continuing.
• The EBPV solenoid is not serviced in the rebuild kit, but the old o-ring should not be reused. Do you really want to pull the turbocharger a second time to fix a serious oil leak? You'll need two o-rings: (1) # 012 x 1/16" cross section and (1) # 013 x 1/16" cross section The # 013 is not a common size in our experience while the # 012 is common to standard o-ring kits. Use a chemical or oil resistant o-ring.
• Reinstall the EBPV solenoid. Make sure to coat the o-rings and bore in clean motor oil and that the EBPV seats entirely when pressed in. You may have to put your weight into it, but you'll typically feel it seat into place. Install the valve stem first, followed by the solenoid body. Lightly torque the top nut - it will unseat the valve stem if it is over torqued. It just needs to be slightly more than hand tight.
• Coat the turbocharger-to-pedestal o-rings in clean motor oil and set them into the oil ports at the bottom of the turbocharger.
• Gently set the pedestal onto the turbocharger and install the (4) bolts. Notice that two of the bolts are longer than the other pair; they correspond with the taller portion of the pedestal casting. Lightly coat the tips of the bolts with high heat anti-seize
• Hand tighten all (4) mounting bolts, then snug them down in a criss cross fashion to seat the o-rings.
• Reconnect the EBPV connector bracket to the compressor housing (10 mm socket). Do not overtighten, lightly snug.
• The final step is to set the EBPV actuator preload force. The piston assembly uses a spring to close the valve when the solenoid closes and oil pressure drops in the actuator cylinder. To ensure proper operation, it is important to set the spring preload to 10 lbs of force. A small pull scale is required.
1) Connect the actuator rod latch to the EBPV.
2) Install a 0.01 inch feel gauge between the EBPV linkage and bump stop (refer to image).
3) Install a small pull gauge above the actuator disconnect fitting and pull straight outwards while holding the turbocharger. When the feeler gauge falls (butterfly valve just begins to open), read the scale. International's preload spec is 10 lbs.
4) Make any appropriate adjustments by lengthening/shortening the actuator. Disconnect the actuator from the EBPV link and rotate the latch inwards (shorten) for more preload and outwards (lengthen) for less preload.
5) Once the preload has been set to 10 lbs, tighten the jam nut against the actuator latch.
Reinstall the turbocharger and test for proper operation. See: 1994 - 1999 7.3L Power Stroke turbocharger installation procedures