The Jetta essentially started out as a VW Golf without the hatchback. As time progressed, the Jetta became more refined and desirable. In the 1999 model year, Volkswagen revamped the Jetta, stepping away from the boxy style and introducing a more aerodynamic style. The 1999 Jetta came standard with a 2.0-liter engine that buyers recognized more as a fuel-efficient engine rather than a powerhouse. Replacing the thermostat in the base 2.0-liter is not a tough task, but you must use extreme care when choosing the coolant for it, as there are two different coolants available for this year and they are not compatible with each other.
Things You’ll Need
- Floor jack
- Jack stands
- Ratchet
- Socket set
- Drain pan
- Slip-joint pliers
- Small flat-head screwdriver
- New thermostat housing O-ring
- Volkswagen G12 coolant
- Torque wrench
- Clean container, 1-gallon
- Clean water
- Clean and sealable container, minimum 2-gallon capacity
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Unscrew the cap from the coolant overflow tank. Raise the front of the Jetta with a floor jack and slide jack stands under the vehicle’s subframe. Lower the Jetta onto the jack stands.
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Crawl under the vehicle and find the under-engine splash guard. Remove the six bolts securing the splash guard using a ratchet and socket. Pull the splash guard rearward to disengage it from the front fascia, then pull it downward to remove it.
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Find the radiator drain assembly next to the lower radiator hose. Position a drain pan under the drain assembly and turn the knob on the drain assembly counterclockwise to open it and start the flow of coolant from the radiator.
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Close the valve once the flow of coolant from the drain assembly stops.
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Move toward the passenger’s side of the engine and find where the radiator hose connects to the engine, just above the oil pan and behind the water pump. The component connecting the hose to the engine is the thermostat housing. Slide the drain pan under the thermostat housing.
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Squeeze the ears of the radiator hose’s clamp with slip-joint pliers and slide the hose clamp about 5 inches away from the thermostat housing. Pull the radiator hose from the thermostat housing with a slight twisting motion.
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Remove the two bolts securing the thermostat housing using a ratchet and socket, and pull the housing from the engine. Pull the thermostat from the engine. Using a small flat-head screwdriver, pry the O-ring from the thermostat housing.
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Coat a new thermostat housing O-ring with fresh Volkswagen G12 coolant; you can identify this coolant by its pink color. Press the new O-ring into the groove in the thermostat housing from which you pulled the old O-ring.
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Guide a new thermostat into the engine with the spring side of the thermostat going into the engine. Rotate the thermostat so the thin metal strip on the exposed side of the thermostat is in a vertical position.
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Set the thermostat housing in place over the thermostat and hand-thread its retaining bolts. Tighten the thermostat housing bolts to 11 foot-pounds with a torque wrench and socket. Press the radiator hose back onto the thermostat housing and slide the hose clamp to about 1/2-inch from the end of the hose using slip-joint pliers.
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Lift the under-engine splash guard upward and align its staggered tabs with the lip on the lower part of the front fascia. Press the splash guard forward until the lip is between the staggered tabs. Hand-thread the six splash guard-retaining bolts, then tighten them with a ratchet and socket.
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Raise the Jetta off the jack stands using a floor jack, and remove the jack stands. Lower the Jetta to the ground.
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Fill a clean, 1-gallon container about 4/5 of the way with clean water. Pour this water into a clean and sealable container with at least a 2-gallon capacity. Add just over a 1/2 gallon – 13/20 of a gallon, to be precise – of VW G12 coolant into the sealable container. Mix the container by sealing it and lightly shaking the container. This creates the 60-40 mixture of water-to-coolant the Jetta requires.
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Pour the mixed coolant into the coolant overflow tank until the level remains steady in the middle of the two lines on the bottom half of the overflow tank.
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Tighten the cap onto the coolant overflow tank, and turn the heater and air conditioner controls to the off position. Start the Jetta’s engine and hold the rpm at 2,000 for roughly three minutes. Allow the engine to idle until the cooling fan turns on, then turn off the engine.
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Check the coolant level. If it is not at the upper line on the coolant overflow tank, slowly unscrew the overflow tank’s cap to allow pressure to escape, then remove the cap. Add VW G12 coolant until the level is at the top line, then close the overflow tank’s cap.
Tips & Warnings
- Engine coolant is highly toxic, and its sweet taste and smell may attract animals and children. If they should drink this coolant, it may result in severe illness and even death. Keep coolant away from children and animals, and always keep children and animals away from your work area.