Mishimoto Pontiac GTO/G8 Aluminum Power Steering Reservoir - Polished

Replace Your Aging Plastic Reservoir With a Polished Aluminum Upgrade Built for the GTO, G8, and Caprice PPV

The Mishimoto MMRT-GTO-04PSP is a direct-fit polished aluminum power steering reservoir engineered specifically for the 2004-2006 Pontiac GTO, 2008-2009 Pontiac G8, and 2011-2013 Chevrolet Caprice PPV. The factory plastic reservoir on these vehicles is notorious for yellowing, becoming brittle, cracking, and leaking power steering fluid over time. The MMRT-GTO-04PSP eliminates that failure point permanently, replacing the OEM unit with a precision-machined, corrosion-resistant aluminum tank finished in a brilliant polished shine. It features -6 ORB and -8 ORB fittings for a grease-free, leak-free connection, mounts to the factory location, and ships complete with all hardware needed for installation.

Why GTO, G8, and Caprice PPV Owners Upgrade

On the GTO, G8, and Caprice PPV platform, the factory power steering reservoir sits on the driver's side of the engine compartment and is retained by a bracket bolted to the cylinder head. These plastic reservoirs are known to yellow, crack at the hose barbs, and seep fluid onto hot engine components. Because it is machined from high-quality aluminum, this tank does not share any of those degradation characteristics. Aluminum is heat-tolerant, corrosion-resistant, and will not warp or become brittle with age. The polished finish also gives the engine bay a clean, finished appearance that complements other underhood upgrades on these LS-powered vehicles.

Features

• Precision-machined from high-quality, lightweight aluminum for maximum durability and corrosion resistance
• Brilliant polished finish for a show-quality underhood appearance
• Direct-fit replacement for the factory plastic reservoir on 2004-2006 Pontiac GTO, 2008-2009 Pontiac G8, and 2011-2013 Chevrolet Caprice PPV
• -6 ORB (O-ring Boss) inlet fitting and -8 ORB outlet fitting for a leak-free, grease-free connection
• O-ring Boss fittings eliminate the need to grease threads or use thread sealant during installation
• Mounts to the factory reservoir location using the included bracket and hardware
• Ships complete with all mounting hardware, no separate purchase required
• Shipping dimensions: approximately 6.40" W x 4.90" H x 8.70" D; shipping weight approximately 1.0 lb
• Available in polished or anodized black (MMRT-GTO-04PSP-BK) finish
• Backed by the Mishimoto Lifetime Warranty

Fitment Reference

Specifications

What's Included

• 1 x Polished aluminum power steering reservoir tank
• 1 x Cap with seal
• -6 ORB inlet fitting
• -8 ORB outlet fitting
• Mounting bracket
• Complete hardware kit (bolts, washers, lock washers, nuts)

Frequently Asked Questions

Will the MMRT-GTO-04PSP fit my 2008 or 2009 Pontiac G8 GT?
Yes. This reservoir is a confirmed direct fit for both the 2008 and 2009 Pontiac G8 GT. It replaces the factory plastic reservoir that clips into the bracket on the driver's side of the engine compartment. The factory reservoir is held by a bracket bolted to the cylinder head with 15mm fasteners. The Mishimoto unit uses the same mounting location and includes its own bracket for a clean, permanent installation.

Does this fit the G8 GXP as well?
Yes. This reservoir fits the 2009 Pontiac G8 GXP in addition to the GT trim. All G8 models share the same power steering reservoir mounting location and hose routing, so the fitment is identical across trims.

Is this reservoir compatible with my 2004, 2005, or 2006 Pontiac GTO?
Yes. This tank is a direct-fit replacement for all three GTO model years. On the GTO, the factory plastic reservoir is a well-documented failure point, particularly around the hose barbs, where the plastic becomes brittle and cracks. This aluminum tank solves that permanently.

Does this fit the 2011-2013 Chevrolet Caprice PPV?
Yes. The Caprice PPV shares the same power steering system architecture as the Pontiac G8 due to their common platform, and this reservoir is a confirmed direct fit for all three Caprice PPV model years (2011, 2012, and 2013). The reservoir location, bracket attachment, and hose sizing are all compatible.

What fittings does this reservoir use, and do I need to grease the O-rings?
This reservoir uses a -6 ORB (O-ring Boss) inlet fitting and a -8 ORB outlet fitting. ORB fittings use a captive O-ring that seals against a machined face rather than thread sealant, which means no thread sealing compound and no greasing of threads is required. This results in a leak-free connection right out of the box.

What power steering fluid does the GTO, G8, and Caprice PPV use?
The GTO, G8, and Caprice PPV all use Dexron VI automatic transmission fluid in the power steering system, not traditional power steering fluid. This is a common point of confusion. Using the wrong fluid can damage the pump and seals over time. Always confirm the fluid specification in your owner's manual before refilling. This reservoir is fully compatible with Dexron VI ATF.

Is there a finish option other than polished?
Yes. Mishimoto offers the same reservoir in an anodized black finish under part number MMRT-GTO-04PSP-BK. The polished version provides a bright chrome-like appearance, while the black version suits builds with a blacked-out underhood aesthetic. Both versions share the same direct-fit construction and fitment.

What is the warranty, and will it void my factory warranty?
The MMRT-GTO-04PSP is backed by the Mishimoto Lifetime Warranty against defects in materials and workmanship. Under the Magnuson-Moss Warranty Act, a vehicle manufacturer cannot void your factory powertrain or vehicle warranty simply because you installed an aftermarket part. The manufacturer would need to demonstrate that the aftermarket part directly caused the failure in order to deny a warranty claim. Keep your purchase receipt as proof of date of purchase for any Mishimoto warranty claim.

Will my factory G8 or GTO hoses connect directly to this reservoir?
This reservoir includes -6 ORB and -8 ORB fittings sized to work with the factory hose routing. The fittings use M12 x 1.0 metric thread. Most owners connect the factory hoses using the provided fittings without additional adapters, though hose condition should be inspected at the time of installation. If your hoses have been previously modified or upgraded to AN-style lines, standard AN-to-ORB adapters are widely available.

How long does installation take?
For a mechanically experienced enthusiast, this installation typically takes between 30 and 60 minutes. On the G8 and Caprice PPV, the factory reservoir unclips from its bracket using a flathead screwdriver. The factory bracket is removed by unbolting it from the cylinder head (15mm socket and extension required) and is not reused. The Mishimoto bracket installs in its place with the provided hardware. The GTO install follows a similar process. Have a drain pan and shop towels on hand before starting.

Do I need to bleed the power steering system after installing this reservoir?
The power steering reservoir is a return-side component and does not hold system pressure. However, air can enter the system any time a line is disconnected. After refilling the new reservoir to the correct fluid level, start the engine and slowly turn the steering wheel from full lock to full lock several times with the cap off. This cycles fluid through the system and allows any trapped air to escape through the reservoir. Recheck the fluid level and top off as needed before replacing the cap. The system does not require vacuum bleeding unless the rack or pump was also serviced.

Installation Instructions

1. Allow the engine to cool completely before beginning. Never work on the power steering system while the engine is hot.
2. Disconnect the negative battery terminal to prevent accidental starting during the installation.
3. Locate the factory plastic power steering reservoir on the driver's side of the engine compartment. The reservoir clips into a bracket that is bolted to the cylinder head.
4. Using a turkey baster or suction pump, remove as much power steering fluid from the factory reservoir as possible before disconnecting any hoses. This minimizes spillage. The GTO, G8, and Caprice PPV use Dexron VI ATF as power steering fluid; keep this fluid off rubber belts and painted surfaces.
5. Place a clean drain pan beneath the reservoir. Loosen the hose clamps on both the inlet and outlet lines using the appropriate driver and slide them back from the reservoir fittings.
6. Carefully pull the hoses off the factory reservoir fittings. Cap or plug the hoses temporarily to prevent additional fluid loss while you work.
7. On G8 and Caprice PPV models, disconnect the two wiring harnesses from the factory bracket before removing it. Pry one harness clip loose and open the second clip to release it from the bracket.
8. Using a 15mm socket and extension, remove the two bolts securing the factory bracket to the cylinder head. Remove the bracket and factory hardware; they will not be reused.
9. Position the new Mishimoto bracket in the factory mounting location and secure it to the cylinder head using the provided hardware. Tighten to a snug, secure fit.
10. Thread the -6 ORB inlet fitting and -8 ORB outlet fitting into the appropriate ports on the new aluminum reservoir. These use M12 x 1.0 metric thread. Tighten securely; no thread sealant or O-ring grease is required with ORB fittings.
11. Mount the new MMRT-GTO-04PSP aluminum reservoir onto the installed bracket. Secure with the provided bolts, washers, and lock washers. Verify the reservoir is seated firmly and will not contact any moving components.
12. Reconnect the power steering hoses to the inlet and outlet fittings on the new reservoir. Slide the hose clamps back over the fittings and tighten securely. Give each hose a firm tug to confirm it is seated properly.
13. Fill the reservoir with Dexron VI ATF (the correct fluid for GTO, G8, and Caprice PPV power steering systems) to the appropriate cold-fill level marked on the reservoir. Do not overfill.
14. Reconnect the negative battery terminal.
15. Start the engine and let it idle. With the reservoir cap off or loosely placed, slowly turn the steering wheel from full lock to full lock three to four times. This cycles fluid through the system and purges trapped air. Watch for air bubbles in the reservoir.
16. Shut off the engine, recheck the fluid level, and top off with Dexron VI ATF if needed. Replace the cap securely.
17. Start the engine again and perform a final inspection of all fittings and hose connections for any leaks. Confirm no hoses are kinked or contacting moving parts before returning the vehicle to service.

WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.