Holden Astra: Thermostat and its plastic housing leak or stick — overheating on a cheap part
Thermostat and its plastic housing leak or stick — overheating on a cheap part is a common cooling fault on the Holden Astra on the 1998–2003 cars, and we rate it major. Putting it right costs $250 to $1,100 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 16 documented faults on the Holden Astra.
- Vehicle
- Holden Astra
- Years
- 1998–2003
- Fuel
- petrol
- System
- Cooling
What you are looking at
Example of the part — not this vehicleA double-valve engine thermostat, labelled: the wax capsule is what sticks.
What goes wrong
The TS Astra's thermostat sits in a plastic housing on the engine, and both the housing and its gasket are a recurring problem: owners report replacing thermostats repeatedly, gaskets weeping, and thermostats sticking shut so the engine overheats within minutes of setting off. Several TS owners also report going through more than one water pump. None of these parts is expensive on its own, but an overheated aluminium engine is, and this generation has form for getting hot quickly rather than giving a slow warning. Using the wrong coolant makes it worse: owners who ran generic green coolant instead of the correct type report water pump corrosion within a few years. A car with fresh, correctly coloured coolant and a recent thermostat invoice is a much better bet than a clean-looking one with an unknown history.
What you would notice
- Temperature gauge climbing quickly, sometimes within a few minutes of setting off
- Gauge that never reaches normal, or swings up and down
- Coolant weeping from the housing, leaving crusty residue on the engine
- Heater blowing cold, or hot and cold in turns
- Coolant that looks brown, murky or the wrong colour in the bottle
How to check it
Where to look. Thermostat housing on the engine where the bottom radiator hose connects, and the coolant bottle at the side of the engine bay
Look into the coolant bottle with the engine cold and check the level against the marks and the colour of the fluid: it should be clear and brightly coloured, not brown, murky or oily.
Feel the bonnet before you start it so you know the engine really is cold, then start it and watch the temperature gauge continuously for the first ten minutes of driving, because on this car overheating tends to arrive fast rather than creeping up.
The needle should rise steadily to the middle and then stay there through both town driving and open road.
Use your phone torch to look around the thermostat housing on the engine for crusty white or coloured residue and for a wet film.
Ask the seller when the thermostat, housing and coolant were last replaced and what coolant was used.
What it costs to put right
$250 to $1,100 at New Zealand independent workshop rates. That is for this job on its own, not for the car.
Ask the seller
- “When were the thermostat and its housing last replaced?”
- “Has this car ever overheated? What happened afterwards?”
- “What coolant is in it, and when was it last changed?”
Now check the Holden Astra you are actually looking at
Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.
Where this comes from
- ProductReview.com.au — Holden Astra TS (1998-2005) owner reviews: repeated thermostat replacements, leaking thermostat gasket, second water pump, coolant type causing water pump corrosion
- Whirlpool Forums — 'Holden Astra 02 overheating in 3 minutes of drive' thread
- Whirlpool Forums — '2005 TS Astra temperature problems' thread
Holden Astra buyer questions
Is thermostat and its plastic housing leak or stick — overheating on a cheap part serious on a Holden Astra?
We rate it major and common on the Holden Astra. The TS Astra's thermostat sits in a plastic housing on the engine, and both the housing and its gasket are a recurring problem: owners report replacing thermostats repeatedly, gaskets weeping, and thermostats sticking shut so the engine overheats within minutes of setting off. Several TS owners also report going through more than one water pump. None of these parts is expensive on its own, but an overheated aluminium engine is, and this generation has form for getting hot quickly rather than giving a slow warning. Using the wrong coolant makes it worse: owners who ran generic green coolant instead of the correct type report water pump corrosion within a few years. A car with fresh, correctly coloured coolant and a recent thermostat invoice is a much better bet than a clean-looking one with an unknown history.
How much does it cost to fix on a Holden Astra?
$250 to $1,100 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.
Which Holden Astra years are affected?
Our research records this fault on the 1998–2003 Holden Astra. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.
How do I check for it before I buy?
Look into the coolant bottle with the engine cold and check the level against the marks and the colour of the fluid: it should be clear and brightly coloured, not brown, murky or oily. Feel the bonnet before you start it so you know the engine really is cold, then start it and watch the temperature gauge continuously for the first ten minutes of driving, because on this car overheating tends to arrive fast rather than creeping up. The needle should rise steadily to the middle and then stay there through both town driving and open road. Use your phone torch to look around the thermostat housing on the engine for crusty white or coloured residue and for a wet film. Ask the seller when the thermostat, housing and coolant were last replaced and what coolant was used. Look here: Thermostat housing on the engine where the bottom radiator hose connects, and the coolant bottle at the side of the engine bay