Have an old toyota and was told recently that the thermostat was not working and was jammed open.
I've not noticed any difference recently and the car seems to run just fine.
Could anyone advise a novice on how to tell if there is a problem with the thermostat (ie how to determine if it's jammed open) and what difference a defective one would make?
If it is jammed open, the car will be unlikely to reach proper working temperature, so the temp needle will read below normal, the heater may be low output, and the car may waste petrol.
If you can get it out of the car you can throw it in some boilling water and watch it open and close as it cools
Take it for a longer run and get up to speed, but at gentle throttle. If the temperature goes down, the stat is jammed open.
johnson formulated on Wednesday :
Start the car from cold, letting it tick over, keep checking the top hose from the radiator to the engine. If the thermostat is stuck open the top hose will warm up gradually, if it warms up quite suddenly the thermostat is doing it job. Doing its job, may not mean that it is opening at exactly the right temperature though, but likely it will be.
If you can get it out of the car you can throw it in the bin and replace it with a new one. They're not exactly expensive.
Not without testing the old one, there's no point having a false sense of confidence that it is 'fixed' if there is nothing wrong with the old one.
Exactly what I would do, having done the boiling water trick in the past. You have to at least replace the casting and top up the water/antifreeze to drive to the spares shop, or go on the bus. ;-)
On a VW Golf, at least, that description might actually just mean the sender unit is on the way out, as mine recently was.
All the best, Angus Manwaring. (for e-mail remove ANTISPEM)
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More than once I've found a failed/failing thermostat in one of my kids' cars by taking it for a test drive when I service it. I have a nice long fast down-hill run to watch the temp gauge on.
The kids say that the car runs just fine. Nor can I pick up the failed thermostat by just driving.
Part of not noticing the problem is their not taking my advice and keeping fuel consumption records.
John
In message , John Henderson writes
I've done that since the early 60's when it had to be done with a calculator and graph paper. It alerted me to a partly blocked main jet when it dropped dramatically. There were other clues like having to keep the loud pedal pressed. :-)
Now it's easy with a spreadsheet.
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