Understanding the Coolant-Integrated Intercooler

A coolant-integrated intercooler, such as the APS GT-R system, uses engine coolant to cool the intake air charge rather than relying solely on ambient air. This design offers several advantages for high-performance vehicles like the Nissan GT-R: more consistent intake air temperatures, reduced heat soak in stop-and-go traffic, and the ability to maintain peak power during sustained boost sessions. By integrating the intercooler into the vehicle’s existing coolant loop, you create a closed-loop thermal management system that keeps charge air temperatures low even under extreme loads.

Before diving into the installation, it is critical to understand that this upgrade is not a simple bolt‑on replacement. It requires careful integration with the coolant system, proper bleeding, and often a tune adjustment to fully realize the performance gains. The following guide provides a comprehensive walkthrough for a safe and effective installation.

Tools and Materials Needed

Having the correct tools and parts on hand before you start will save time and prevent frustration. Beyond the basic socket set and wrenches, you will need:

  • APS GT-R coolant-integrated intercooler kit – includes intercooler core, brackets, and all necessary hardware
  • Socket set (metric, ¼” and ⅜” drive recommended)
  • Combination wrenches (10 mm to 19 mm)
  • Torque wrench (ft‑lb and in‑lb ranges)
  • New coolant (manufacturer‑specified type; often Nissan Long Life Antifreeze / coolant mixed 50/50 with distilled water)
  • Silicone coolant hoses and worm‑gear clamps (if not included in kit)
  • Safety glasses and mechanic’s gloves
  • Shop towels or rags
  • Drain pan (minimum 5‑gallon capacity for the coolant system)
  • Shop vacuum or compressed air (to aid in coolant removal and cleaning)
  • OEM or aftermarket intercooler piping (if the kit requires new routing)
  • Magnetic parts tray (to keep bolts organized)

Optional but recommended: a coolant pressure tester, a scan tool to reset adaptation values, and a helper for lifting heavy components.

Preparation Steps

Workspace and Vehicle Safety

Park the vehicle on a level, well‑ventilated surface. Engage the parking brake and place wheel chocks behind the rear tires. Disconnect the negative battery terminal (using a 10 mm wrench) to prevent any accidental electrical shorts while working near the engine bay.

Draining the Coolant

Allow the engine to cool completely – a hot coolant system is pressurized and can cause severe burns. Place a drain pan under the radiator petcock and under the side of the block drain plug (if accessible). Open the radiator cap to relieve pressure, then open the petcock and allow the coolant to drain. For a more thorough drain, also remove the block drain plug(s) – consult the service manual for your GT-R model year.

Removing Obstructions

To access the intercooler area, you will need to remove:

  • The front bumper cover (follow the manufacturer’s clip‑removal procedure)
  • The crash bar (if it blocks intercooler access)
  • Any factory air intake ducting, horns, or fog lights that obstruct the intercooler mounting location
  • Under‑engine splash shields

Keep all fasteners organized – a magnetic tray or labeled baggies will save hours of searching later.

Removing the OEM Intercooler

The OE intercooler on the GT-R is a large air‑to‑air unit located behind the front bumper. To remove it:

  1. Disconnect the charge air pipes (usually two large silicone hoses with T‑bolt clamps). Label the hoses and plugs.
  2. Unplug any sensors attached to the intercooler (e.g., IAT sensor).
  3. Remove the bolts securing the intercooler to its brackets. Typically there are four to six 12 mm or 14 mm bolts.
  4. Carefully slide the intercooler out from its mounting position. Have a second person support it if the intercooler is large and heavy.
  5. Set the old intercooler aside; you may want to sell it or keep it as a backup.

Tip: Clean the mounting area thoroughly with a shop towel and brake cleaner to remove any oil or debris before installing the new unit.

Installing the APS Coolant-Integrated Intercooler

Mounting the Core

Position the new APS intercooler in the same location as the OEM unit. Align the mounting tabs with the vehicle’s bracket holes. Use the supplied bolts and a torque wrench to tighten them to the manufacturer’s specification (typically 15–20 ft‑lb, but verify with the kit instructions). Do not overtighten – the core is aluminum and can deform.

Connecting Charge Air Piping

Reconnect the charge air pipes to the intercooler inlet and outlet. Most APS kits use a combination of silicone couplers and bead‑loked aluminum tubes. Apply a thin film of silicone lubricant to the inside of the couplers for easier assembly. Tighten clamps to 4–5 in‑lb (do not exceed, or you may crush the piping).

Bracket and Support Modifications

Some coolant‑integrated intercoolers require additional brackets or shims to align properly. The APS GT-R kit typically includes a new crash bar and lower support brackets. Follow the included diagram exactly – incorrect mounting can lead to rubbing, vibration, and eventual failure of the core.

Integrating the Coolant System

Coolant Line Routing

The APS intercooler has coolant inlet and outlet ports (usually two 5/8” or 3/4” barbed fittings). You will need to plumb these into the engine’s coolant circuit. The most common method is to tap into the heater hose circuit or to use a dedicated coolant line from the water pump outlet. The kit includes silicone hoses and splices; if not, purchase high‑temperature coolant hose rated for automotive use.

  1. Identify a coolant supply source – often the water pump bypass or a T‑fitting on the upper radiator hose.
  2. Install a coolant flow direction as marked on the intercooler (usually inlet from the engine’s coolant return).
  3. Use constant‑tension clamps (or worm‑gear clamps) at every junction. Position clamps so they do not interfere with other components.
  4. Ensure hoses do not contact sharp edges, belts, or hot exhaust pipes. Use split loom or heat sleeve where needed.

Filling and Bleeding the Coolant System

After connecting all lines, close any drain valves. Fill the radiator and expansion tank with a 50/50 mixture of appropriate coolant and distilled water. Start the engine with the radiator cap off and allow it to idle. As the thermostat opens, you will see coolant circulate. Carefully add more coolant as the level drops. Squeeze the upper radiator hose to help burp air pockets. Follow this with a coolant system burping procedure using a coolant funnel or a vacuum filler tool. Continue until the level stabilizes at the “FULL COLD” mark and no bubbles appear in the coolant stream.

Final Checks and Testing

Visual Inspection

  • Verify all hose clamps are tight and not kinked.
  • Inspect electrical connectors (IAT sensor, fan connectors) are fully seated.
  • Check that the intercooler is not rubbing against the radiator or condenser fins.
  • Confirm the crash bar and bumper cover are re‑installed correctly.

Use a coolant pressure tester to pressurize the system to the cap rating (usually 16–20 psi). Wait 10 minutes and watch for a drop in pressure – any drop indicates a leak. Repair as necessary.

Road Test and Monitoring

Reconnect the battery. Start the engine and let it reach normal operating temperature. Monitor the coolant temperature gauge – it should remain within normal parameters. Take a gentle test drive, allowing the coolant to cycle through the intercooler loops. After the drive, re‑check the coolant level and top off as needed. Ideally, log intake air temperatures (IAT) using a scan tool – you should see significantly lower IATs under boost compared to the stock intercooler.

Performance Benefits and Tuning Considerations

A coolant‑integrated intercooler offers several performance advantages over traditional air‑to‑air designs:

  • Consistent charge air temperatures – even during extended hard driving, the coolant loop provides a stable heat sink.
  • No heat soak in traffic – unlike air‑to‑air intercoolers that rely on ram air, the coolant‑integrated system keeps air cool even when stationary.
  • Reduced plumbing complexity – the intercooler can be placed closer to the throttle body, reducing turbo lag.

However, this upgrade increases the coolant volume and may slightly raise coolant temperatures if not properly engineered. A high‑flow water pump or a larger radiator might be needed for heavily modified cars. Additionally, because the intercooler exchanges heat with the coolant, it can slightly increase engine coolant temperature under extreme load – monitor your coolant gauges and consider upgrading the radiator if you track your GT-R.

After installation, you should have the vehicle tuned or at least have the ECU adaptation reset. A custom tune can take advantage of the cooler intake air by advancing timing and increasing boost, yielding significant horsepower gains – often 30–50 hp on a Stage 1 GT-R with a supporting tune.

Common Pitfalls and Troubleshooting

  • Air pockets in coolant system: If the cabin heater blows cold or the engine temperature spikes, the system may have an air lock. Re‑bleed using the procedure above.
  • Insufficient intercooler coolant flow: Some installations require a dedicated coolant pump. If you have idle issues or slow warm‑up, check that the coolant lines are not reversed or restricted.
  • Charge air leaks: A hissing sound under boost indicates a coupler or clamp leak. Re‑tighten or replace the coupler.
  • Overheating after installation: This could be a result of reduced radiator airflow (if the intercooler is too thick) or an overtaxed cooling system. Consider a higher‑capacity radiator or an auxiliary cooler.

Maintenance and Long‑Term Care

Periodically inspect all coolant hoses for cracks, swelling, or leaks. Flush the coolant system every two years or 30,000 miles to prevent scale buildup that can clog the intercooler’s internal passages. Also check the intercooler core for debris accumulation – a soft brush and water can clean the front fins without damaging them.

External Resources

Conclusion

Installing a coolant‑integrated APS GT-R intercooler is a rewarding upgrade that can significantly improve engine performance and reliability. By following this detailed guide – from tool preparation and removal of the OEM unit, to coolant integration, bleeding, and final testing – you can ensure the installation is done correctly the first time. The result is a vehicle that pulls harder in every gear, resists heat soak, and delivers consistent power on the street or track.

Always prioritize safety: work with a cold engine, wear protective gear, and never rush the bleeding process. With the right preparation, you’ll unlock the full potential of your GT-R’s forced‑induction system.