Parts for your 1998 Ford Falcon-Thermostat

1998 Ford Falcon Thermostat – purpose, fitment and servicing

Per Ford’s EL and AU Falcon workshop manuals and well-known repair guides such as Gregory’s Ford Falcon 1998–2002, the 1998 Ford Falcon absolutely uses a thermostat. Both the 4.0‑litre inline‑six (late EL and early AU) and the optional 5.0‑litre Windsor V8 are liquid‑cooled engines with a wax‑pellet thermostat. On the six, it sits in the housing at the front of the cylinder head where the top radiator hose connects, on the V8 it’s located in the intake manifold outlet. So yes—thermostat fitment is relevant for this model.

The thermostat’s job is to help the Falcon warm up quickly and then hold a steady operating temperature, typically around the low‑90s °C as specified in Ford service literature. It stays shut while the engine is cold, then opens progressively to control coolant flow through the radiator. That means quicker cabin heat, better fuel economy, lower emissions, and consistent performance even on hot Aussie and Kiwi days.

Owners and techs watching for thermostat trouble will usually notice one or more of these signs:

• Overheating or coolant boiling after a short drive
• Very slow warm‑up and poor heater output
• Temperature gauge hunting up and down, or sudden spikes
• Top radiator hose staying cold, then going scalding hot all at once
• Cooling fans running excessively to compensate

As part of routine cooling‑system servicing on a 1998 Falcon, the thermostat isn’t strictly a scheduled replacement item, but it’s smart to assess it whenever coolant, water pump, radiator, or hoses are being replaced—especially on higher‑kilometre cars. If there’s any doubt, fit a quality thermostat matched to the factory temperature rating and use a new gasket or O‑ring. Clean the housing faces, orient the bleed jiggle‑pin (if fitted) to the top, and tighten the housing bolts evenly. Refill with the correct Type A glycol coolant at the recommended mix, set the heater to hot, bleed air patiently, and verify the fans cycle and the gauge stabilises. After the first proper heat‑soak and a road test, recheck for leaks and top up the overflow bottle once the engine is fully cold. Preventative replacement every decade or so can be cheap insurance, particularly in Falcons that tow, idle hard, or see big temperature swings.

Popular questions about 1998 Ford Falcon thermostats

Where is the thermostat on a 1998 Ford Falcon?
On the 4.0‑litre inline‑six (late EL/early AU), it’s in the alloy housing at the front of the head where the top radiator hose attaches. On the 5.0‑litre V8, it’s under the thermostat neck on the intake manifold at the front of the engine. Access is straightforward with basic hand tools and a catch tray.

What temperature rating should be used?
Factory specifications in Ford manuals call for a thermostat around the low‑90s °C for everyday road use. Lower‑temp units exist, but for most street Falcons they can lengthen warm‑up, increase fuel use, and upset engine management. Sticking with the OEM‑equivalent rating is the safe bet.

How do you bleed the cooling system after replacing the thermostat?
Set the heater to full hot, fill the radiator and overflow bottle with the correct coolant mix, then start the engine and let it idle with the cap off until the thermostat opens and air purges. Squeeze the upper hose gently to help release bubbles. Fit the cap, bring the engine to operating temperature, allow a cooling cycle, and top up the bottle cold if needed.