Why Upgrade Your Audi S5’s Intercooler?

The Audi S5’s 3.0-liter supercharged V6 is a robust power plant, but like all forced-induction engines, it’s susceptible to heat soak. As intake air temperatures rise, the engine management system pulls timing and reduces boost to protect the engine—dramatically cutting power. A larger, more efficient intercooler lowers intake air temperatures, allowing the engine to maintain peak output run after run. Wagner Tuning’s intercooler kits are engineered specifically for the Audi S5 (B8, B8.5, B9 chassis), offering up to 40% more core volume and superior fin density compared to the factory unit. The result is more consistent horsepower, reduced knock risk, and improved fuel efficiency under load. This guide walks you through a complete DIY installation, covering every fastener, hose clamp, and test drive check. Whether you’re chasing drag strip times or simply want a cooler-running daily driver, this upgrade delivers measurable gains.

Tools and Materials You’ll Need

Before lifting a wrench, gather the following. Missing a tool mid-job can turn a three-hour install into a weekend project. We’ve grouped items by function for clarity.

Wagner Tuning Kit Contents

  • Wagner Tuning intercooler (cast aluminum end tanks, bar-and-plate core)
  • High-quality silicone hoses (two pieces, with reinforced layers)
  • Stainless steel T-bolt clamps (all sizes needed)
  • Mounting brackets and hardware (specific to Audi S5 chassis)
  • Instruction manual (review before starting)

Hand Tools

  • Socket set: 8 mm, 10 mm, 13 mm, 16 mm deep sockets
  • Combination wrench set (10 mm, 13 mm)
  • Torx bits: T25, T30, T45 (for bumper and underbody panels)
  • Flathead screwdriver (medium size for prying clips)
  • Phillips screwdriver (No. 2)
  • Torque wrench (range 5–80 Nm)
  • Trim removal tools (plastic pry bars – highly recommended to avoid scratching paint)

Consumables & Safety Gear

  • Genuine Audi G12 or G13 coolant (about 2–3 liters for bleeding)
  • Distilled water (if mixing coolant)
  • Small funnel and coolant bleeding funnel
  • Rags or shop towels
  • Protective gloves (nitrile or mechanic’s gloves)
  • Safety glasses

Preparing Your Audi S5 for the Install

Park on a level surface and let the engine cool completely—ideally overnight. A hot cooling system can spray scalding coolant when you disconnect hoses. Place wheel chocks behind the rear tires, and raise the front of the car on jack stands if you need more working room (though the job can be done from the ground with the car parked).

Safety First

Disconnect the negative battery terminal. This prevents the electric cooling fans from kicking on unexpectedly, and avoids any short circuits while working near sensors. Use a 10 mm socket to loosen the terminal clamp, then secure the cable away from the battery post. Wear safety glasses when working under the car—debris and coolant splashes are common.

Engine Bay Preparation

Remove the engine cover (if equipped) by pulling straight up on the four rubber grommets. This gives you access to the charge air pipes and the top of the intercooler. Also remove any plastic trim panels that bridge the front of the engine bay to the bumper. In some S5 model years, there is a small cross-brace between the strut towers that must be removed (two 13 mm bolts each side).

Step-by-Step Intercooler Installation

We break the process into five phases. Work slowly and double-check each step—forcing components can damage the new intercooler or the vehicle’s radiator support.

Phase 1: Remove the Front Bumper and Grille Assembly

This is the most time-consuming part for first-timers, but it’s straightforward if you follow the fastener pattern. Audi uses a mix of screws, bolts, and spring clips.

  • Remove the under-engine splash shield (10 mm screws and a few T25 Torx). You’ll need to access the lower bumper attachments.
  • Remove the upper grille trim. On B8/B8.5 S5s, there are two T30 Torx screws at the top of the grille frame, plus plastic clips along the sides. Use a trim tool to gently release the clips—pull the grille forward once all are free.
  • Remove the lower bumper grilles (if equipped with adaptive cruise or fog lights, unplug connectors).
  • Locate the bumper mounting bolts: two 16 mm bolts on each side inside the wheel well liners (turn steering to full lock for access), and four 13 mm bolts along the top of the bumper carrier. Some models have an additional 10 mm bolt behind each headlight access panel.
  • With all fasteners removed, pull the bumper straight forward. A helper makes this easier—the bumper is heavy and has wiring for fog lights and parking sensors. Gently lay it on a clean blanket to avoid scratching.

Pro tip: Place tape on the paint edges where the bumper meets the fenders to prevent accidental scuffs during removal.

Phase 2: Remove the Stock Intercooler

With the bumper off, the factory intercooler sits prominently behind the radiator. It’s a black plastic-and-aluminum unit approximately 25–30 mm thick.

  • Drain the coolant. Locate the drain plug on the bottom of the radiator (passenger side) or remove the lower radiator hose. Have a drain pan ready. Expect about 4 liters to come out. Alternatively, you can clamp the hoses to minimize loss, but draining gives you a cleaner workspace.
  • Disconnect the two charge air hoses from the intercooler: one on the driver side (inlet from supercharger) and one on the passenger side (outlet to throttle body). Loosen the T-bolt or spring clamps with a flathead screwdriver or 8 mm socket. Slide the hoses off the plastic barb fittings.
  • Remove the two or three bolts securing the intercooler to the radiator support (typically 10 mm). On some S5 versions, the intercooler also has two lower push-pins that slide into rubber grommets—pull the intercooler upward to release them.
  • Carefully lift the stock intercooler out. Rotate it slightly to clear the condenser lines. Compare its dimensions with the new Wagner unit—you’ll immediately see the increase in core thickness (from ~25 mm to ~40 mm) and the full cast aluminum end tanks.

Phase 3: Install the Wagner Tuning Intercooler

Before mounting the new intercooler, inspect the silicone hoses from the kit. They should have a smooth inner bore and no debris. Apply a very thin film of silicone grease (included in some kits) to the hose interiors to ease installation onto the intercooler and the vehicle’s charge air pipes.

  • Position the Wagner intercooler in the same orientation as the stock unit. The inlet and outlet ports face the same direction. Slide the new intercooler down into place, ensuring the lower rubber grommets (if reused from stock) seat properly. If the kit includes new brackets, install them now before tightening.
  • Secure the intercooler using the supplied bolts. Torque to 8 Nm (6 ft-lb)—overtightening can crack the aluminum mounting tabs. Check that the intercooler sits level and does not contact the radiator or condenser. A gap of about 5 mm all around is ideal.
  • Attach the charge air hoses. Start with the driver-side outlet (pipe from supercharger). Slide the hose fully onto the intercooler barb, then tighten the T-bolt clamp just snug. Do the same on the passenger side. Do not fully tighten until everything is aligned—you may need to rotate the hoses slightly to avoid kinking.
  • Once both hoses are connected and aligned, torque the T-bolt clamps to 5 Nm (3.7 ft-lb). Over-tightening can collapse the silicone hose or strip the stainless band.

If your S5 uses an auxiliary electric coolant pump (early B8 models), ensure its hose routing does not interfere with the new intercooler. Some owners choose to relocate the pump slightly—the Wagner kit’s included brackets accommodate this.

Phase 4: Refill Coolant and Bleed the System

Now reconnect the coolant lines. Audi uses spring clamps—they are reusable, but if any feel weak, replace with worm-gear clamps. Push the hose onto the intercooler’s coolant barb until it seats over the ridge, then secure with the clamp.

  • Pour a 50/50 mix of G12+ and distilled water into the expansion tank. Fill slowly to avoid air pockets. Stop when the level reaches the “cold” max line.
  • Run the engine with the heater set to “HI” and fan on low. Let it idle, and as the thermostat opens, you’ll see coolant level drop—add more. Use a coolant bleeding funnel if available (this simplifies the process and prevents spills).
  • Once the engine reaches operating temperature and the upper radiator hose is hot, shut off the engine. Let it cool, then recheck coolant level. Top off as needed. Repeat the bleed cycle until no air bubbles appear in the expansion tank.

Phase 5: Reassemble the Front End

Refitting the bumper is the reverse of removal, but pay attention to alignment.

  • Reattach the bumper by aligning the slides on the top of the bumper carrier. Push the bumper straight back until the spring clips engage. Listen for distinct clicks on each side.
  • Install the bumper bolts: torque the 16 mm wheel well bolts to 25 Nm (18 ft-lb), the top 13 mm bolts to 15 Nm (11 ft-lb).
  • Reinstall the grille, splash shield, and engine cover. Reconnect the battery negative terminal.
  • Before lowering the vehicle, turn the steering lock to lock to ensure the wiring for the wheel well sensors is clear and the bumper sits flush with the fenders.

Post-Installation Testing and Validation

Rushing the test drive can mask issues like loose clamps or a minor leak. Follow this systematic check:

  • Visual inspection: With the engine running, look for coolant drips at the intercooler hose connections and the radiator drain plug. Also listen for any air hissing from the charge air hoses. A small leak under boost will cause a significant performance drop.
  • Short idle test: Let the car idle for five minutes. The electric fans should cycle on once or twice. If the engine overheats, you likely have an air lock in the cooling system—bleed again.
  • Road test (light load): Drive gently for 5–10 minutes, keeping RPM under 3000. This allows the ECU to relearn fuel trims and ensures no boost leaks at low pressure. Monitor the coolant temperature gauge—it should stay within normal range (90–100°C).
  • Full boost run: Find a safe straight road. From a rolling start in 3rd gear at 2500 RPM, floor the throttle to redline. You should feel a stronger pull from mid-range onward compared to stock. The engine should not “fall on its face”—if it does, you likely have a boost leak. Pull over and retighten all charge air clamps.

Data logging: If you have a VCDS (VAG-COM) or OBD-II datalogger with IAT (intake air temperature) monitoring, compare pre- and post-install logs. Stock intercooler IATs often climb 30–40°C above ambient during a 3rd gear pull. With Wagner, expect a rise of only 10–15°C. Lower IATs mean the ECU does not pull timing, giving you more consistent power.

Common Issues and Workarounds

  • Hose too stiff to slide onto intercooler fittings: Dip the end of the silicone hose in hot water (70°C) for 30 seconds to soften it. Never use oil or soap—they can degrade the rubber.
  • Bumper not aligning after reinstall: Check that the intercooler is not pushing the crash bar forward. The Wagner unit is designed to fit within the stock envelope, but an unsecured hose can bind. Loosen the intercooler hardware, shift it slightly, and retighten.
  • Coolant leak at intercooler fitting: The O-rings in the kit must be lubed with a tiny amount of silicone grease. Replace the O-rings if they appear cut or pinched.

Performance Gains and Efficiency Results

After a proper install, the Wagner Tuning intercooler provides measurable benefits. Independent tests on the 3.0T engine show up to 15–20 horsepower gains on a stock tune simply from reduced heat soak. The gains multiply if you run a stage 1 ECU tune—where the stock intercooler becomes a bottleneck. With the Wagner unit, IATs stay low enough to allow continuous back-to-back pulls without power fade. Fuel efficiency also improves on hot days because the engine does not enrich the mixture to cool combustion chambers. Many owners report a 5–10% increase in highway mpg when towing or climbing grades.

For those considering further upgrades, the Wagner intercooler provides a solid foundation. It works seamlessly with upgraded supercharger pulleys, intake systems, and cat-back exhausts. The bar-and-plate core is also less prone to charge air temperature spikes under sustained high boost, making it ideal for autocross, track days, or spirited mountain drives.

External Resources

For additional technical data and community feedback, consult these sources:

Final Thoughts

Swapping the factory intercooler for a Wagner Tuning unit is one of the most effective bolt-on upgrades for the Audi S5—it unlocks consistent power, reduces engine stress, and improves drivability in all conditions. While the bumper removal requires patience, the process is well within the reach of a competent DIYer with basic tools. Every component in the Wagner kit is designed to fit without cutting or modification. Take your time on the coolant bleed, torque all fasteners to spec, and do a thorough boost-leak test. With the new intercooler in service, your S5 will pull harder, run cooler, and be ready for whatever driving situation comes next.