Question about 1999 GMC Sierra
Ok, if you have it narrowed it down to a specific area, try narrowing it down further by using a long (2foot or more) extension or screwdriveras a "stethescope". Hold one one end against your head in front of your ear and probe different areas near the noise 'till you hear it the loudest, (I'm not kidding... this works) Be careful where you put the probe... the engine is running... stay away from drive belts and any other rotating stuff!
With what you have said, I'm sort of leaning towards a valve lifter at this point. PS: which engine is this?
The oil pressure thing concerns me... What is the exact pressure at idle hot and cold? what about at 1500rpm? If you have not been doing regualr oil changes, you could have something simple like gummy residue. If you have been using a high parafin based oil (usually really cheap stuff) this can happen even with properly timed oil changes. (once saw an engine with similar miles with enough sludge in it to make two softball sized globs just using what I found inside the valve covers, yet oil was changed every 3000 miles!) Though I don't like promoting products, I recommend changing your oil now, using any good synthetic and a pint of Marvel oil +good oil filter. (unless you have been using similar all along) See if after a few days the fluctuations in pressure and noise diminish somewhat. Get back to me on questions I asked.
Posted on Dec 14, 2008
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Posted on Jan 02, 2017
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