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Thread: intermitant temperature variations...

  1. 26th June 2007, 09:44 PM #1
    EchiDna's Avatar
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    intermitant temperature variations...

    non landy question, but possibly applicable to all vehicles...

    I've got a little buzzbox over here in Singapore that drives well and doesn't miss a beat, and yet recently the temperature spikes upwards almost to the overheating area for a few seconds, then drops back down again to normal (half scale on the gauge) and cycles through this for a couple of minutes. When I stop, the engine is definitely hotter than normal, so I don't think it's sensor related.... possibly the water pump giving up the ghost slowly?

    coolant is full and clean, oil is clean... but there are some 'unusual sounds' that aren't identifiable and so far not reproducable once stopped with the bonnet up....

    any thoughts? my mind says water pump, but with the cap off and thermostat out the water is certainly circulating consistantly (but that intermitant noise aint there either when I look).
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  2. 26th June 2007, 10:02 PM #2
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    thermostat disloged/failed, water pump failing, excess debry in the cooling system. failed radiator pressure cap, collapsing lower radiator hose


    he first is easy take the thing out see what happens

    the second take the belt and pully of and see what play you have and how smooth the roataion is, nothing like 30 od HP to make a waterpump look like its turning smoothly

    Drop the bottom radiator hose off and see what comes out if you get flakes thats bad... this can be intermittant as the coolant flow slows the debry begins to settle and then once it does coolant flow returns so the engine cools down as the coolant flow increases as the coolant flow increases it picks up debry which........

    the collapsing lower radiator hose does the same thing...

    and finally check and replace the radiator cap... assuming its not a fancy cooling system with oil-coolant and charge air-coolant heat exchangers thats the simple cheap stuff covered...
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  3. 26th June 2007, 10:24 PM #3
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    Quote Originally Posted by Blknight.aus View Post
    thermostat disloged/failed, water pump failing, excess debry in the cooling system. failed radiator pressure cap, collapsing lower radiator hose


    he first is easy take the thing out see what happens

    the second take the belt and pully of and see what play you have and how smooth the roataion is, nothing like 30 od HP to make a waterpump look like its turning smoothly

    Drop the bottom radiator hose off and see what comes out if you get flakes thats bad... this can be intermittant as the coolant flow slows the debry begins to settle and then once it does coolant flow returns so the engine cools down as the coolant flow increases as the coolant flow increases it picks up debry which........

    the collapsing lower radiator hose does the same thing...

    and finally check and replace the radiator cap... assuming its not a fancy cooling system with oil-coolant and charge air-coolant heat exchangers thats the simple cheap stuff covered...
    thanks Dave...

    thermostat is already out, has been since before i got it...

    will check the rest shortly, hoses have swollen around the clamps, so could have swollen inwards as well time for a a few hours under the hood...
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  4. 26th June 2007, 11:43 PM #4
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    Running with no thermostat can cause issues too.
    (from what I was told once)
    The coolant flow isn't being regulated, it can flow too fast and not actually draw any heat out of the metal, and this can cause hot spots around the cylinder walls.
    Actually boiling the coolant in localized spots.
    This could be the temp fluctuations you see.
    I think from memory, you need the coolant flow slow enough to transfer the maximum heat energy into it, but not too slow as to cause boiling,
    (or too fast as for above reason)

    plausible?
    1999 110 Defender 'Extreme' TD5
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