I have a 99 Olds Intrigue GLS with the 3.5L Shortstar engine.
It has a definite knocking sound that occurs on startup, not too
noticeable in the car with doors closed, but definately there.
It has not gotten any worse and oil consumption is about average for
what I hear for this car. Sometimes needs more between changes and
other times it does not need any additional.
Crankshaft postion sensor already replaced.
What could this be? Think it is a definite sign of impending engine
failure or is it something that will just be a minor annoyance?
Sounds like bad lifters, but, im no mechanic.
Car has 65,000 miles and runs well otherwise.
Two things come to mind with this engine. A very uncommon
but serious problem with these engines was the failure of
the front balance shaft bearing. This bearing is like a cam bearing
that you would find in a small block chevy engine, same idea.
We've had about 3 of the 3.5 engines that had this bearing
actually come right out of the block and then the balance shaft
just begins to spin right into the aluminum block (which essentially
destroys the block). Usually, the sure sign of this happening
is no lack of oil pressure on the guage, but you get a lot of
lifter noise, simply because the front balance shaft bearing is
right in line with the oil passage that goes from the block and
then up to the cylinder heads. As a result, a failure of that
bearing causes the oil pressure to drop off up to the heads.
The other item that we see much more of....is just carbon buildup
on the pistons which can cause this noise. There is a de-carbonization
procedure that GM uses for oil consumption on the Northstar engines.
We use this same procedure for carbon buildup on the pistons, and
for the most part it's fairly successful.
We don't see too many engine failures of any kind with these
3.5 engines. Pretty solid little engine.
No, you pull the plugs, inject the cleaner
into the cylinders and let it sit for between
2 and 3 hours. Then it gets sucked out,
plugs re-installed, oil drained and refilled,
given a good hard road test, then change
the oil and filter again.
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