91 SI rebuilt motor eats litre of oil per week!!!

Discussion in 'General Motoring' started by RayGun, Aug 11, 2005.

  1. RayGun

    RayGun Guest

    Hey All.. I rebuilt my daughters 91 Si, had burned and bent exhaust
    valves. Put in new rings, valves, valve seats, gaskets and all the
    necessary items needed. Break-in period was gentle and 2000 kms.
    It passed the emission test no sweat, but after about three months
    started to go through more an more oil.
    Compression test showed all cylinders up to snuff, ( haven't done a
    leak-down test) but the exhaust pipes are full of soft coal!!! and there
    is definitely smoke under exceleration and decel. No oil on
    undercarriage, no drips, no leaks from rocker cover...?????
    Anyone had this experience...and what remedy
    Thanx for any help.
    RayGun, Aug 11, 2005
  2. RayGun

    jim beam Guest

    two possibilities:

    1. assuming the rebuild was good, check the coolant level. look in the
    radiator, not the expansion bottle. if you don't have the correct
    coolant level, the temp sensor is not getting the right signal and it
    tells the motor to go into cold start mode. that injects excess gas,
    dilutes the oil film on the cylinder walls & suddenly, it's consuming
    oil. also check/replace the thermostat & the oxygen sensor. but i
    doubt this would be as bad as a quart a week.

    2. you mention replacing rings, but not pistons. when you replace
    rings, you need to re-hone the cylinder wall to break up the glaze layer
    for the new rings to bite. re-honing usually means new pistons. if you
    didn't hone, the rings will never seal and it'll drink oil. in
    addition, all traces of abrasive need to be removed from the cylinder
    wall after honing too. re-built engines almost always have a much
    accelerated wear rate compared to factory because this vital step of
    cylinder honing abrasive removal is either overlooked or done badly.
    excess wear = excess oil consumption.
    jim beam, Aug 11, 2005
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