I have been advised by an experienced "car guy" to change the thermostat on my 94K miles 2005 Toyota Matrix, although everything seems to be fine at the moment. Everybody else is telling me to leave it be until there are problems. It it were easy I would just do it, but it seems like it is going to be a rather involved process, or I would have to pay someone to do it. What do you think I should do?


This may fall into the "Automotive Urban Legends" category. Many years ago it was advised to change your coolant every year. The coolant broke down and the corrosion inhibiters failed to control rust. Pieces of rust would clog radiators, heater coils and thermostats. With the advent of long life antifreeze service intervals have been extended. If your 2005 has never had the cooling system serviced I would suggest new hoses, a system flush, new coolant. If the coolant looks muddy or rusty I would consider changing the thermostat. If changing the heater hoses is beyond the budget (some of these are vehicle specific and can get costly) do the upper and lower radiator hoses at the least.

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    While a heater hose failure doesn't cause as big a leak (as they're smaller), they'll still empty the system pretty fast. In my experience, the heater hoses are more likely to fail than the main hoses too. If I was concerned enough to replace the main hoses, I'd definitely be replacing the heater hoses. – Brian Knoblauch Jun 28 '13 at 14:08
  • Ok, so do change the hoses, and check the coolant fluid to see if a thermostat change is in order. Thanks! – Pierre Jun 28 '13 at 16:52
  • The only hoses I've ever had fail have been ones that were subject to extreme heat from cooling system failure, and they were not the main upper/lower hose. I think replacing hoses as preventative maintenance is also "automotive urban legend". The only time I'd overhaul a cooling system is if it were allowed to operate for a long time with poor cooling efficiency (e.g. a clogged radiator). – R.. GitHub STOP HELPING ICE Jun 29 '13 at 0:59
  • @R.. : I think replacing hoses as preventative maintenance is also "automotive urban legend" Sorry, I think you are completely wrong here. I have seen way too many 10-15-year-old cars with cracked or squishy hoses. Rubber is the fastest thing to degrade under the hood of a car. Replacing the hoses is cheap insurance compared to total loss of coolant and overheating, especially considering how many engines have aluminum heads nowadays (which can be warped or cracked and destroyed by a single episode of overheating). – dodgethesteamroller Jun 29 '13 at 19:13

If it ain't broke don't fix it.Thermostats are generally easy to remove and test with hot water and a thermometer to ascertain that they open at correct temp.Workshop manual shows how.When reassembling ensure all mating surfaces are clean;use new gasket and check for corrosion of housing as they are sacrificial

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