2018 Ford Explorer Coolant Flush — Complete DIY Guide

The 2018 Ford Explorer with the 3.5L EcoBoost twin-turbo V6 is a capable SUV, and its cooling system works hard — two turbochargers add significant heat load that the factory cooling system is sized to handle. Keeping the coolant fresh is more important here than on naturally aspirated engines, and dealers charge $150–$200 for the service. You can do it yourself for $40–$60.

The critical detail: the 2018 Explorer uses Ford's orange OAT (Organic Acid Technology) coolant — Motorcraft Specialty Orange Engine Coolant. Do not use universal green, HOAT (yellow or orange "universal"), or Dex-Cool. Mixing coolant chemistries causes gel buildup that clogs the cooling system.

What You'll Need

• Coolant: Motorcraft Specialty Orange Engine Coolant (VC-3-B or VC-3DIL-B for pre-mixed)
  • Approximate total system capacity: 14.8 quarts for the 3.5L EcoBoost Explorer
  • Buy 1–1.5 gallons of pre-mixed 50/50 for a drain-and-fill; 3 gallons for a full flush
• Distilled water (not tap water — minerals in tap water accelerate corrosion in aluminum components)
• Drain pan (2-gallon minimum capacity)
• 8mm or 10mm socket (radiator petcock or lower hose clamp — confirm your drain access point)
• Funnel
• Safety glasses and gloves (coolant is hot when warm and toxic — keep it away from pets)
• Ramps or jack stands for drain access

Estimated time: 60–90 minutes Estimated cost: $40–$60 in coolant (vs. $150–$200 at a Ford dealer)

Before You Start — 3.5L EcoBoost Cooling System Notes

The 3.5L EcoBoost has an electronically controlled thermostat and a fairly sophisticated cooling system that maintains tighter temperature tolerances than older V6 engines. A few things to know:

1. Thermostat housing location — The thermostat on the 3.5L EcoBoost Explorer is located on the passenger side of the engine, at the rear, where the lower radiator hose connects to the engine block. When following the lower radiator hose from the radiator, you'll find the thermostat housing where it connects to the engine. This is important for bleed procedure positioning.

2. No traditional petcock on some builds — Some 2018 Explorer cooling systems drain from the lower radiator hose clamp rather than a petcock drain. Check your specific vehicle.

3. Electronic thermostat — The 3.5L EcoBoost uses an electronically actuated thermostat (electric coolant temperature control). It functions normally during a DIY flush — no special considerations — but if you see erratic temperature gauge behavior after service, an OBD-II scan for coolant-related codes is worth checking.

Step-by-Step Instructions

1. Let the engine cool completely — Minimum 2 hours. The 3.5L EcoBoost operates at high coolant temperatures — opening the system when warm causes scalding coolant to erupt from the reservoir.

2. Locate the coolant degas bottle (overflow reservoir) — On the 2018 Explorer, the pressurized coolant reservoir is the degas bottle on the passenger side of the engine bay. Remove the cap slowly — confirm there's no residual pressure by listening for a hiss before fully removing.

3. Locate the radiator drain point — Check the lower-left corner of the radiator for a petcock. If present, open it counterclockwise. If there's no petcock on your specific vehicle, loosen the hose clamp on the lower radiator hose at the radiator end and carefully pull the hose partially free to drain.

4. Drain the old coolant — Position the drain pan. The 3.5L EcoBoost Explorer holds nearly 15 quarts — use a large drain pan. Let it drain 5–10 minutes.

5. Initial flush — Close the drain/reinstall the hose. Fill the system with distilled water through the degas bottle to the MAX COLD line. Start the engine and let it reach operating temperature (approximately 185–195°F). The thermostat will open, circulating water through the entire system. Shut off, let cool completely, then drain again.

6. Repeat flush if needed — If the drained water looks brown, rust-colored, or cloudy, repeat the distilled water flush. The goal is relatively clear drain water before adding the new coolant.

7. Close the drain and add new Motorcraft Orange coolant — Pour Motorcraft Specialty Orange into the degas bottle to the MAX COLD line.

8. Bleed the air from the system — Start the engine. Leave the degas bottle cap off. Let the engine reach operating temperature and hold for 10–15 minutes. Watch the coolant level in the degas bottle — it will drop as air is displaced and the thermostat opens. Keep topping up to MAX with fresh Motorcraft Orange coolant. You'll see bubbles escaping from the degas bottle as air works out of the system.

9. Check the thermostat housing for air pockets — The passenger-side thermostat housing location can trap air. Some 2018 Explorer owners find it helpful to gently squeeze the upper radiator hose while the engine is warm to help work air bubbles toward the degas bottle.

10. Install the cap once no bubbles appear — When the coolant level in the degas bottle has stabilized at MAX and no more air bubbles are visible, install the cap.

11. Check level cold — After the engine cools completely (next morning), check the degas bottle cold level. Should be at or slightly above MIN in a cold system.

12. Check for leaks — Inspect the drain point, hose clamps, and degas bottle area after 10–15 minutes of driving.

Pro Tips / Common Mistakes

• OAT Orange only — Motorcraft Specialty Orange (not the standard Motorcraft green). The 3.5L EcoBoost cooling system has aluminum components, turbocharger intercooler plumbing, and specific corrosion inhibitor requirements. Wrong coolant accelerates corrosion.
• Don't skip the air bleed — The 3.5L EcoBoost can trap air near the thermostat housing and in the turbo coolant lines. An air pocket that doesn't get bled causes a hot spot, erratic temperature gauge, and potential heater core damage. Take the extra 15 minutes to do it right.
• Check all hose clamps after service — A hose that was dripping during the flush may have a weakened clamp. Inspect and replace if needed.

Cost Comparison: DIY vs. Shop

	DIY	Ford Dealer
Coolant 1.5 gal	$25–$40	Included
Labor	$0	$100–$140
Total	$25–$40	$150–$200

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