Bypass Thermostat Overview

Fig 1: Bypass Thermostat, Assembly Overview

Courtesy of VOLKSWAGEN UNITED STATES, INC.

1. Retaining Clip
2. Lower Part of Housing
3. Operating Element
4. Spring
5. O-ring
6. Upper Part of Housing

Checking the Bypass Thermostat:

-- Remove the operating element.

-- Warm the operating element in a coolant bath.

Starts to open: approximately 75°C (167°F).

Opening end: approximately 85°C (185°F).

Opens: approximately 5 mm

Bypass Thermostat Location:

The bypass thermostat for the transmission fluid cooler circuit:

Arrow on the bottom part of the thermostat points to the heater core.

The bypass thermostat for the turbocharger coolant circuit:

Arrow on the bottom part of the housing points to the coolant recirculation pump.