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Autopapyrus · JAC JS4 1.5 Turbo 156 hp (2024)
https://autopapyrus.com/guides/jac/js4/thermostat-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

JAC JS4 1.5 Turbo 156 hp (2024): Thermostat Replacement

On this turbo engine, the thermostat is usually mounted in a plastic or aluminum housing on the coolant hoses. Signs of failure: the engine takes a long time to warm up, overheats or the temperature fluctuates, and the heater blows cold air. A precise step-by-step procedure for this model is not documented in public sources, so below is the general principle for liquid-cooled turbo engines. Check the location and number of fasteners on the vehicle itself.

Difficulty: Medium Time: 2-3 hours Steps: 11 Tools: Socket set and ratchet (8-13 mm), screwdriver, hose clamp pliers, drain pan (5 L (5.3 qt) or larger), funnel, rags, torque wrench, new gasket or O-ring. A spill-free coolant filling funnel is useful for bleeding the system.

Part

  • 🔩 Thermostat with housing, plus a new thermostat housing gasket or O-ring and coolant (antifreeze) of the same type as is in the system. The exact part number is not given, to avoid errors. Match the part by VIN or by the old part: JAC turbo engines come with thermostats that have different opening temperatures

Step by step

11 steps
  1. Wait until the engine has cooled down completely. Do not open the coolant reservoir cap on a hot engine, or you risk burns from steam and hot coolant.
  2. Remove the lower engine undercover if fitted. Place the drain pan under the radiator and open the drain valve or disconnect the lower radiator hose. Remove the reservoir cap and drain the coolant. A full drain is not needed; it is enough to lower the level below the thermostat housing.
  3. Locate the thermostat housing. It is usually where the large radiator hoses connect to the engine block or cylinder head. If the air duct, turbocharger hose or intercooler hose is in the way, carefully remove it, noting the clamp positions.
  4. Take a photo of how the hoses and sensors are connected, then disconnect the temperature sensor connector on the housing, if there is one.
  5. Loosen the clamps and pull the hoses off the housing. If a hose is stuck, do not cut it; gently twist it free. Inspect the hoses and replace any that are cracked or swollen.
  6. Remove the thermostat housing bolts (usually 2-4 bolts, 10-13 mm socket), take off the housing and remove the thermostat.
  7. Clean the mating surface of any gasket residue and scale, without leaving scratches and without letting debris fall into the passage. Install the new thermostat in the correct orientation, with the valve or tab facing up, the same way the old one was installed. Fit a new gasket or O-ring.
  8. Tighten the bolts evenly in a crisscross pattern. The torque for thermostat housing bolts is usually low, about 8-15 N·m (6-11 lb-ft) (check the exact value in the manufacturer's specifications). A plastic housing cracks easily if overtightened.
  9. Reinstall the hoses, clamps, sensor connector and any air ducts you removed. Close the drain valve.
  10. Fill with coolant up to the MAX mark. Start the engine with the reservoir cap open, set the heater to maximum and let it run until the thermostat opens (the upper hose becomes hot and the radiator fan switches on). Top up the coolant as air escapes. Squeezing the hoses to help bleed the system should only be done very carefully.
  11. Close the reservoir cap and warm the engine up to operating temperature. Make sure there are no leaks at the connections and that the heater works. Shut off the engine, let it cool, then check the level again and top up if needed.

Common mistakes and warnings

  • Do not drive with an air pocket in the cooling system: on a turbo engine this is a quick path to overheating and cylinder head warping. If the temperature gauge climbs toward the red zone, shut off the engine immediately. A 2024 vehicle may still be under warranty, and doing the cooling system work yourself could complicate a warranty claim, so check the terms first. If you have no experience working on cooling systems, have a repair shop do the replacement.
How it works · 3D How the Engine Cooling System Works How the part you're working on actually works — in plain English, on a 3D model. Open in 3D →