2005 GMC Savana 1500 - 4.3 engine /auto
About 85,000 on engine - installed used about 10,000 miles ago. No maintenance history on used engine - have used Mobil ! since installation.
All was great until about six months ago when a loud (apparently) lifter noise occurred one morning. It would go away after a few miles but come back after a day or two. Oil was not low. I added a can of SeaFoam, the noise went away, didn't come back, I changed the oil and filter, and forgot about it.
Now, six months later - the noise is back, although maybe a bit less loud. Oil is up to the mark. But this time I noticed that while the noise is happening the oil pressure at idle and in gear is about 10 lbs. Neutral and reving to maybe 2000 rpm gets the oil pressure close to 80 lbs. Idle in neutral and it's back to about 18 lbs.
A couple miles, the noises goes away, and the oil pressure acts normal again: idles at about 20 and is about 40-42 running at 50 mph.
Can any one point me in the right direction? Maybe can think of a correlation between the weird oil pressure action and the "lifter noise". It's sharp and metallic - nothing like a rod or main bearing knock.
Any ideas? <g>
About 85,000 on engine - installed used about 10,000 miles ago. No maintenance history on used engine - have used Mobil ! since installation.
All was great until about six months ago when a loud (apparently) lifter noise occurred one morning. It would go away after a few miles but come back after a day or two. Oil was not low. I added a can of SeaFoam, the noise went away, didn't come back, I changed the oil and filter, and forgot about it.
Now, six months later - the noise is back, although maybe a bit less loud. Oil is up to the mark. But this time I noticed that while the noise is happening the oil pressure at idle and in gear is about 10 lbs. Neutral and reving to maybe 2000 rpm gets the oil pressure close to 80 lbs. Idle in neutral and it's back to about 18 lbs.
A couple miles, the noises goes away, and the oil pressure acts normal again: idles at about 20 and is about 40-42 running at 50 mph.
Can any one point me in the right direction? Maybe can think of a correlation between the weird oil pressure action and the "lifter noise". It's sharp and metallic - nothing like a rod or main bearing knock.
Any ideas? <g>