Symptoms
- Overheating symptoms beginning shortly after a thermostat replacement
- Poor heater performance suggesting trapped air
- Possible gurgling sounds from the dashboard or engine bay
- Gauge behavior different from before the replacement, sometimes worse
Likely causes
- CommonTrapped air not properly bled after the coolant was drained and refilledAny time the cooling system is opened for a repair like this, air needs to be purged using the correct procedure.
- CommonThermostat installed backward or in the wrong orientationSome thermostats have a specific orientation, and installing one backward can prevent proper coolant flow.
- PossibleDefective new thermostatOccasionally a replacement part can be faulty out of the box.
- PossibleGasket or O-ring not seated correctly, causing a leak that lowers coolant levelAn improperly seated gasket can leak, gradually reducing coolant level after the repair.
What to do
- Check the coolant level and top off if it's low.
- Follow the correct bleed procedure for your vehicle to purge trapped air from the system.
- If you or someone else did the replacement, double check the thermostat's orientation against the installation instructions.
- Check around the thermostat housing for any new leak from an improperly seated gasket.
- Avoid continuing to drive if overheating is significant; pull over and let it cool as with any overheating situation.
- Have the installer recheck their work first if a shop did the repair, since this is often covered under the original service.
- Have a mechanic verify thermostat orientation and function, or test for a defective part, if a proper bleed doesn't resolve it.
Tools and parts
- Gloves
Thermostat and gasketSearch: “thermostat for [make model year]”
When to call a pro
Go back to whoever did the thermostat replacement first, since an installation or bleed issue from that repair is a common and typically covered cause.
Safety
Use caution
Pull over and let the engine cool at the first sign of overheating rather than continuing to drive.