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temperature gauge and overheating

I have a 2001 Toyota Camry with 187,000 miles. My temp gauge moves into the red area when driving up hills or idling for long periods of time. If it gets hot enough the coolant backs into the overflow tank. Have replaced sensor that controls the fan, thermostat, water pump, had the radiator flushed and replaced coolant. Sometimes gauge will go back to normal very quickly but later rise again. Spark plugs are coolant free and no noticeable leaks and antifreeze level remains the same. What could be wrong? Cost?

Comments

  • edited June 2009
    [b][i]A Couple Of Ideas:[/i][/b]

    Assuming the guage is correct;

    Was air properly "purged" from the cooling system when it was serviced? Air trapped in the high point of the system will cause problems. I would follow proper procedures and "burp" the system.

    When you say, "[i] . . . and no noticeable leaks and antifreeze level remains the same.[/i]", are you checking the level in the radiator (ENGINE COLD) as well as what you see in the recovery tank? You need to be sure the radiator is full.

    Is the cooling fan(s) working when car is hot? Do they come on when you turn the A/C on?

    Was the radiator cap replaced with the proper cap when the system was serviced?

    If the coolant is low in the radiator, post back.

    CSA
  • edited June 2009
    All of those things that CSA mentioned are great things to check. A 2001 with 187K on it might still have a fine cooling system, but if service has not been done regularly, or you have hard water, the radiator might be shot. Does the temp go down immediatly, even when climbing or idling, if you turn on the heater? Is the radiator clear of debris, fore and aft?
  • edited June 2009
    What are the proper procedures to "burp" the system? We had it flushed and filled at a oil change shop so I'm not sure if they burped it but they were aware of my problem. Will it 'self burp' after a period of time?

    The cooling fans are working and it does come on when the AC is on

    The radiator has not been replaced and the cap is original. This is the only thing I haven't replaced yet but the mechanic seemed to think it was okay. The mechanic (not too bright) can't find anything wrong with it but I haven't taken it to the dealership for fear of being raped.

    I have been checking antifreeze levels regularly since this overheating starting occurring in November. The first time it overheated it was low and I added some antifreeze but since then levels have remained full when the engine is cold.

    In the last month or two the engine is burning a little oil. It was half a quart low and then maybe a month later it was a half a quart low again. It has been about 2800 miles since my last oil change. It has been regularly changed since I purchased the car with 22k miles. The overheating problem has been ongoing much longer (Nov 08) but it may be time to put the ole' Camry to rest. I really wanted to get another year out of it.

    I do have hard water here and maybe neglected to have the radiator flushed regularly. Yes, turning the heater on will lower the temperature gauge immediately as long as I'm not climbing hills (live in the mountains but sometimes the smallest of inclines will make the gauge go up some). Temp gauge will also go down when I crest a hill and enough air flows over the engine. If idling the turning on the heater will make it go down. Is that bad news?
  • edited June 2009
    I would have suspected radiator with almost 200,000 miles before replacing the waterpump.Radiator is partially plugged, needs replaced.
  • edited June 2009
    When the radiator was flushed, wouldn't they be able to tell if there was an obstruction? The radiator looks great, no rust, no debris. Is there a test that can determine if the radiator is plugged? My husband is convinced it is not the radiator but he was wrong about the waterpump. Is there a test that can determine if my car is in fact overheating or if by chance, (oh please) my gauge could be lying?
  • edited June 2009
    oops, meant to reply to you but accidently posted a comment to myself. see below at 5:02:01pm on 6/16. Radiator?
  • edited June 2009
    some radiator shops may be able to flow test the radiator. but with that mileage i would have the radiator replaced. make sure someone checks to see if it has a blown head gasket. put tester on raditor to test for exhaust gases
  • edited June 2009
    Yes, there is a test. A shop can put a test gage "T'd" in with your regulat sensor and measure the actual temperature. But the coolant "back[ing] into the overflow tank" tells me that the engine actually is overheating.....OR the radiator cap isn't holding pressure like it should. The cap can be tested, but for $15 you can replace it. The cap is supposed to keep the fluid pressurized at (typically) about 16 PSI (the rating is stamped on the cap). If it isn't the engine will overheat more readily. Fluid under pressure boils at a higher temperature than fluid that is not.

    Refer back to CSA's post.

    Oh, and "burping" simply means releasing an air bubble. They can get trapped in a high spot in the system, generally in a hose, and restrict flow. Cars prone to this will typically have a small valve at one of the hose's high spots.
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