2000 Chevrolet Blazer Zr2 Cold start knocking from engine

Artie Gustafson

Asked by Jan 27, 2015 at 10:59 AM about the 2000 Chevrolet Blazer 2 Door LS 4WD

Question type: Maintenance & Repair

I have 2000 Chevrolet Blazer Zr2, it has about 148,000 miles. When i start MY truck up in the morning the engine knocks, not severly or violently but there is definetly some light knocking. The knocking will increase in tempo when I increase the throttle as well. When the truck warms up after 2-3 mins the knocking stops and it sounds fine. Also, at cold starts I noticed that the oil pressure gauge is reading really high but then once the truck warms up it goes back to normal. I have noticed no power changes from the  engine just a cold start knocking. Also Oil levels are full. What could this be and how do I fix it?

2 Answers


Your oil viscosity might be affected by the cold weather, if you're living in the north, otherwise use oil for high-mileage engines. Higher oil pressure at startup could be due to the oil being thicker at lower temperatures. Make sure you haven't overfilled the oil. Try changing the oil to a recommended viscosity for your climate/mileage and see how it affect the noise. - One other consideration too, is an exhaust leak, it goes away once the vehicle has warmed up. You'll have to put your ear to the engine (mech's stethoscope or long screwdriver) might help just where the noise is coming from.

1 out of 1 people think this is helpful.

Vortec piston slap. Most of them do it. Has something to do with the material the piston is made from expanding at a different rate when it warms up. I had a full size that made that noise until it warmed up for years. Never used a drop of oil. Still running at near 250K.

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