Expert: Sean Halliday - 5/30/2007

Question
QUESTION: I have a 1985 Toyota Tercel SW 4 WD, it does not overheat while driving it but as soon as you shut it off the temp soars and if you start it again the gauge is reading hot and the temp light is on.  Do you have any suggestions?

ANSWER: I assume you checked the coolant,while the engine is cold.It could be a faulty temp sensor.You will need to see if the coolant is low or leaking and you didnt say how many miles are on the engine.

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QUESTION: Yes the coolant has been checked while cold.  The car is well broken in with about 126,000 miles on it.  The coolant shows to be full with no leaks.  Normally I would think it might be a faulty temp sensor but after the car has been sitting a couple of minutes the hood will almost burn you so I believe it is really getting too warm.
ANSWER: With the amount of miles on the engine,i think its time to replace the head gasket/water pump and flush out the coolant.The gasket may be ready to blow anyway.Check the coolant tank isnt blocked and the passage is clear so the coolant is returning to the bottle/radiator.I assume the fan is working?....electronic i think which works off the sensor even though the car is shut off.More than likely a flow problem which makes the engine hotter when its shut off.

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QUESTION: The head gasket was changed about 6 months ago because when we started driving the car it had a burned valve which had to be replaced therefore so did the head gasket.  The water pump has not been changed as far as I know.  How would I know if that is bad/ how would I check it?  The fan is working when the car is running.  After the temp gets half way up the guage the fan kick on and then off again in a few minutes, but it does not stay running once the car is shut off.  I don't know if it should or not.  We have run a cycle of Prestone Radiator flush through it again tonight and hopefully we might see a difference tomorrow.  When the flush was drained it was a yellowish orange color I am assuming because of rust.
ANSWER: It is possibly rust but try a new thermostat also.The thermostat wasnt fitted the wrong way by chance?Is the heater working ok?As you say the hood gets warm,these cars do run very hot as all japanese engines do.The only real accurate way to tell is get a digital tester and point it at the engine while it is running and shut off.Most alloy engines run at 80,90,degrees centigrade which is acceptable.

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QUESTION: My husband did change the thermostat a month or so ago and it was properly installed.  Where might I get a digital tester and would you happen to know the price range for one of those.  Is it possible that the engine isn't really overheating when shut off and it is just the norm for this motor?  I have never driven a foreign made car *only chevrolets* so I don't know what the norm is.  I do know that it has only overheated one time while driving it and after the new thermostat was put in that hasn't happened since.
ANSWER: A tester costs about $40....if you have a harbor freight tools store near you they have one.Or you can go on ebay .The norm for these engines is to run hot but with the light coming on then it could be a faulty temp sensor so the best way to tell is use the thermometer.These are very accurate and you only have to point it at the engine to read the exact temp.Most jap engines as i said run betweeen 80-90 centigrade.If you look at a thermostat for most jap engines they are calibrated to open at 80-90 centigrade.

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QUESTION: Well, I don't know if this could be my problem or not but on my way to take my husband to work this morning the water pump sprung a really bad leak and is going to have to be replaced.  Of course when that happened it overheated but luckily I was keeping an eye on it pulled over before going into the red.  Is it possible that the water pump could have been my problem all along even though it wasn't leaking?

Answer
Looks like the problem ok.It will leak after you stop but as it gets worse then it just lets go completely.Fit a new one and you should be ok.Do the usual things like check all the belts while youre in there,,,,have a good look at the hoses also and general color of the coolant.