Help - I'm Burning Oil!

[Peter Styer]

I purchased my 1999 Forester with 62,000 miles about 30 days ago. It has a
manual transmission and the 2.5L engine. I've driven it about 4000 miles
and the engine has used 10 quarts of oil! That's 400 miles per quart of
oil!

Compression test shows all cylinders about the same, 155 to 170 psi range
Reving the engine above 4000 rpm, yeilds dark black smoke out the exhaust
pipe.
There are no external leaks from the engine or transmission area.
There is no smoke in the exhaust at start up.
Spark plugs may have a slightly brown dark ash, but the engine is running
fine with no misfires or fouling of plugs.
The well for Spark plug #1 was full of oil when I pulled the plugs.

I think the valve seals are leaking, but is there something else I may be
overlooking?
How difficult is replacing valve seals? Will I need to pull the camshafts
or just the rocker assembly?

Thanks for all your help!
Pete

 

[Carl 1 Lucky Texan]

You may very well have some bad seals BUT ,if you want a shot at slowing
the leakage, clean or replace the PCV valve (and maybe the tubing as well).


Carl
1 Lucky Texan

 

[Edward Hayes]

There is a seal on the cylinder/tube that the spark plug go into. That may
be why you have oil on the plug so just replace them. I suspect the PVC
valve as the "Texan" said. Probably or hopefully not valve stem seals. eddie

 

[ed]

Bad valve seals will cause smoking at idle, when the vaccuum in the engine
is highest, pulling oil past the seals and burning. To check, let the engine
idle when warm for a few minutes, then accelerate the engine a little. Bad
seals will show up as smoke in the exhaust. If no smoke, oil must be leaking
from somewhere that may not be obvious. Seals can be changed in place, but
it's not a very DIY job.
Ed B.

 

[Lance B]

There is a seal on the cylinder/tube that the spark plug go into. That may
be why you have oil on the plug so just replace them. I suspect the PVC
valve as the "Texan" said. Probably or hopefully not valve stem seals. eddie

Dark black smoke from the exhaust means too rich fuel ratio. If it
was grey/blue smoke THIS would mean burning oil. Are you sure about
the colour of the smoke from the exhaust? Generally if the valve stem
seals are leaking you will see the blue/grey smoke after idling at
stop lights for a while. Are you sure there is no leak from the motor
somewhere dripping to the ground?

 

[Peter Styer]

Sorry - I forgot to mention that I replaced the PCV valve after driving
about 3000 miles. The old one appeared to be working. The plunger inside
the valve slid back and forth just like the new valve.
Peter

 

[Peter Styer]

It's definitly black oily smoke.

There are no external leaks. The engine was cleaned by the dealer and is
spotless underneath. In fact, in thirty years of working on engines, this
is the cleanest engine I've ever owned.

Peter