The Haynes manual says to remove the thermostat and re-install the housing without the thermostat to flush the system. If you saw what is required to remove the thermostat housing, you would understand why I didn’t do that the first time at 60K. Now it has 120K and It’s time to do it again. I know the heater core will not get a good flushing but would you go through the hassle? New gaskets for the housing and coolant pipe are required. If I do it should I replace the thermostate while it’s apart?
I would remove the thermostat in order to replace it. Yes, they can be a bear sometimes but are one of those really inexpensive little parts where failure can lead to very expensive consequences (warped head, blown gaskets etc from overheating). Routinely replacing the thermostat is just a good idea as a preventative so that you avoid its failure.
So I’d say its time to bite the bullet - do it all at once.
I don’t know why you are bothering with a flush in the first place. Since you are following the maintenance schedule, a simple drain and replace is all you need. You can pull the plug in the block and open the petcock in the bottom of the radiator to get most of the old coolant out.
Flushing can introduce more impurities than it removes. It is best to just drain what you can and refill with fresh antifreeze and distilled water. The new antifreeze will have enough corrosion inhibitors to carry you through for another five years.
Flushing is a last ditch effort in the hopeless pursuit of salvaging a poorly maintained system.
I agree. The car is ten years old. You should replace the thermostat just to be on the safe side.
How long are you willing to gamble that the original thermostat will not fail and cause problems?
If you really don’t want to do it yourself you could probably get your local independent mechanic to do it for you at a reasonable rate.
keith makes a very good point about the flusing. But I’d still be thinking about changing the thermostat. It is something that a lot of people do just as part of cooling system maintenance. Of course, if you are completely vigilant about watching your gauges you could let it ride. But it may also decide to act up at the worst possible time & place.
Unless the old fluid stayed in too long and looks crappy skip the flush.
I believe in changing the thermostat every 4-5 years, in most cases.