Loss of engine oil
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  1. #1
    WLB
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    Default Loss of engine oil

    I thought this might be worth posting as it seems to be a trap for the unwary. I have encounter 2 cases in the last month. In the first instance it was on a dark night between Warrnambool and Bendigo and if I'd asked more questions before offering to drive the old guy to buy oil, I would have saved myself the extra drive. The second case was my wife, even though I'd told her of the first. (Maybe she'd stopped listening after she heard the word "car").

    Anyway, it seems that quite a few people don't realise this, and it needs to be understood.


    If the engine loses enough water reasonably quickly from a split in a heater or radiator hose for example, the level of water can drop below the water pump before the engine overheats.

    When this happens, the water tends to stop circulating through the system properly and so the temperature sensor for the temperature gauge or warning light may no longer be giving a correct reading.

    The engine will overheat, but the gauge or warning light may not show it.

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    As the oil overheats it becomes much thinner and oil pressure is lost and so the oil warning light come on.

    The driver stops and checks the oil and there appears to be none on the dipstick.

    They believe that they've run out of oil and add more.

    They drive off only to have it happen again, because the engine is still dangerously low on water.

    When everything cools down they find that the engine is now over-full with oil and probably the head has been cooked.


    So, those of you who are not entirely engine-savvy, remember this.
    It is very unusual to lose a large amount of engine oil suddenly and if you do, it will be accompanied by mess and smoke.

    If the oil light comes on, the engine seems very hot and there appears to be no oil on the stick, let it cool, wipe the stick and check it again, looking closely. Very hot oil is very runny and will drain off the stick. It won't show the usual distinct level mark.

    Then check your radiator as you are most likely low on water.

    Warwick.

  2. #2
    Fellow Frogger!
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    Hi Warwick,

    Yes, a trap for the unwary. I think a stove hot head/block combination, plus the usual smoke & odours from overheated metal & grease is another sign that all is not well.

    Another variation to the running hot saga is the removal of the thermostat from the cooling system, in an attempt to correct overheating problems.

    The coolant is now circulated to quickly within the block / radiator, giving insufficient time for the coolant to absorb heat from the surrounding metal, thus actually increasing the total engine temperature.

    It does not seem to happen with every engine type, thus other engines simply run too cold, causing all the associated inefficiences due to poor thermal efficiency.

    Cheers,
    Kim.

  3. #3
    Gone Fishin' Ray Bell's Avatar
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    Default

    While I appreciate what you're trying to say here, you left out a few important things...

    When the car pulls up after running this far without sufficient water, there will be smoke coming off every crevice on the head and block, it will probably be crackling audibly. Most likely it will have by now blown a head gasket or warped or even melted the head so it won't be running right, and even if it hasn't it will be pinking like there's no tomorrow.

  4. #4
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    Default No water circulation - no heater

    Happenned to me many years ago - on a cold night the heater suddennly went cold, so pulled over to check under bonnet and radiator hose had split, strangely no steam coming out from under the bonnet?

    Lucky that I stopped when the heater went cold as the water level loss stopped the hot water circulating through the heater matrix and even on a cold night it would not have taken long to overheat the motor.

    Spare radiator hose fitted, water added (very slowly) and we were on our way half an hour later - no ill effects - but I consider myself very lucky I stopped and and also that it was a cast iron head and block so less likely to warp.

    You can be lucky sometimes, but my brother recently tried to drive his AU Falcon home slowly when a hose split, result warped head and $600 plus garage bill. I thought he would have known better than to try that. and he IS in the RACV but doesn't believe in mobile phones

    Ken

  5. #5
    1000+ Posts Gamma's Avatar
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    The paint blistering off the head and block is a dead give away.

    This type of failure was common on the Holden’s with the 202 motors where the thermistor/sender unit was at the very top and centre of the head. If the thermostat failed to open on a cold morning and you just went out and drove, there would be insufficient circulation in the head to do any real cooling. The water would boil out leaving the sender in gas/steam alone, (this in combination with a radiator cap of the wrong pressure, (8-14lb, depending on model)), spelt disaster.
    I am still amused to see persons wondering why the temp warning light in a 30-40 year old car did not come on after some cooling circuit failure. The dammed things only came on to tell you your motor was done to a tender turn, when new. Ones that old are lucky not to be blown.

    Standard after market fitment of a Smiths combination analogue temp and oil pressure gauge in any Holden I had purchased in the last 20 years. I also advise having a look at the dial every now and then.
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  6. #6
    WLB
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    Quote Originally Posted by Ray Bell
    When the car pulls up after running this far without sufficient water, there will be smoke coming off every crevice on the head and block, it will probably be crackling audibly. Most likely it will have by now blown a head gasket or warped or even melted the head so it won't be running right, and even if it hasn't it will be pinking like there's no tomorrow.
    You would think so; but not necessarily so. That's why I raised it.

    Yes the engine will be very hot and smelly and "creaking", but this may go unnoticed by the non-mechanical person. How hot is too hot if you don't look under the bonnet much anyway? I got to my wife's car about 20 mins after she stopped and rang me. Even then I thought the engine was too hot just from the smell of metal, whereas she thought it "seemed a bit hot" when it first happened.

    In both cases, they only noticed loss of power in the relatively short interval before stopping, and both cars drove normally once refilled with water. This of course does not mean that there won't be head gasket problems on the horizon, or the possibility of considerably reduced engine life.

  7. #7
    WLB
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    Quote Originally Posted by KIMDEB
    Another variation to the running hot saga is the removal of the thermostat from the cooling system, in an attempt to correct overheating problems. The coolant is now circulated to quickly within the block / radiator, giving insufficient time for the coolant to absorb heat from the surrounding metal, thus actually increasing the total engine temperature.
    Yes, good point Kim. The other factor involved here is that to get good heat transfer you need a temperature differential between the 2 materials, so the cooler the water passing through the radiator, the less heat that is transferred to the air moving through it.

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