Anonymous asked in Cars & TransportationMaintenance & Repairs · 8 months ago

when over heat an engine, does that usually cause the pistons to get scored? or the cylinders? or rings? which one first, second and third?

can explain why?

talking about not having enough oil in the engine etc.


like which would happen first, second and third?

if the pistons are not scored, does that mean that the cylinder walls are probably okay? what about rings?

6 Answers

  • not
    Lv 7
    8 months ago
    Favorite Answer

    All metal parts expand with heat. Overheating expands them to the point that the piston is too large for the cylinder it goes in. Friction gets excessive; scoring and melting of piston takes place. There is no 1st 2nd or 3rd; it all happens together.

  • ?
    Lv 7
    5 months ago

    You need to understand normal heat generated from combustion.  There are some very hot places inside an engine. 

    Part of that heat goes out the EXHAUST PIPE. 

    The rest gets transferred to other places, like into the valves and CYLINDER HEAD which gets transferred into the coolant;

    into the PISTONS which is transferred into the cylinder metal and into the coolant; and into the engine oil on the bottom side. 

    I believe the hottest place is the exhaust valves, perhaps 1200° F. 

    The next hottest place is the center of the top of the pistons, perhaps 600° F. 

    When the heat being absorbed into and dissipated by the cooling system suddenly stops, the pistons get hotter.  With this increase in temperature, the aluminum piston expands more.  If it's in an iron cylinder, which can't change size as much as an aluminum piston, the piston to cylinder clearance decreases. 

    If the engine is having oil starvation, then immense friction results. 

    Tighter piston, less lubrication, causes the aluminum to gall.  That makes even less or no clearance.  The story goes on and on.  The engine comes apart.  Often in pieces. 

    -Engine overhaul mechanic and general overhaul mechanic since 1972

    • M.
      Lv 7
      5 months agoReport

      But with a simple, short duration overheat, and the driver pulls off the road right away, and shuts the engine off, none of these things happen.

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  • Anonymous
    8 months ago

    to me this sounds like a mechanics test....or schooling.  If you don't know then LEARN IT.  You deserve to get it wrong. You deserve not to be a mechanic.

    Sorry; that is the way it goes.

    I always have enough oil in my engine.

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  • Anonymous
    8 months ago

    Often, head wharps first, and blown head gasket if Al head.

    Main bearings melt.

    The rings can then over expand,and scuff  cylinder walls, causing seizing or  oil plumping.

    Pistons can melt, yes.

    Much is due to loss of coolant or loss of cooling due to stopped fan, stuck thermo, clogged radiator;  but loss of oil can cause last  3.

    An overly lean mixture can cause high heads temps, too. 

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  • 8 months ago

    Not enough oil in the motor doesn't cause over heating the way no coolant causes over heating. Lack of doing 3,000 mile oil changes and keeping the oil level topped up will cause the piston rings to seize in the piston grooves which causes oil to burn more.

    The crankshaft and connecting rod bearings get worn and seize up

    Source(s): Mitsubishi Master Tech
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  • Anonymous
    8 months ago

    Mechanics do not WORRY about that stuff.  They REPLACE or REBUILD the engine and move on so they can get PAID.

    If it is a leaf blower, THROW IT AWAY.

    • "pistons". NST as multi cylinder leaf blower--at least, not stock.

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