Loud Tapping/Grinding Noise on Cold Start for a Few Seconds

[Legend11]

I have a 2001.0 QX4 and have noticed a problem with the car since I've had it for the past month. When the car is cold (first thing in the morning, after work, etc... anytime it sits for a longtime) it starts rough: loud tapping/grinding noise and then it goes away after a few seconds. To me it sounds like the oil circulates the engine and keeps the parts lubricated. I can start the car when it is warm and this problem doesn't happen; only when it's been sitting for a while. I'm concerned that it is something serious, but I'm hopeful it's not. Any ideas? Also, I just changed the oil to try to fix this problem and it is still happening. Could it be something else? Thanks

[zach7685]

The same thing happens to me. Check your oil level when cold.

[Buzzman]

How many miles on it, and what grade and type of oil are you running?

[Mark Mellott]

I use CD2 oil detergent every other oil change to keep build up and deposits from forming. These deposits and build up can make your hydraulic lifters sticky which will make noises like you have described. This type of sticky lifter issue also has the symptom of making more noise at cold start ups and less or no noise when the engine is warmed up. You can get CD2 oil detergent at AutoZone. Use one or two bottles of the product but do not overfill the crankcase. You may have to drain some oil before adding the product so you do not overfill it. If deposits are the problem, this oil detergent will stop or reduce the noise in 100 miles or less. I hope this is all it is.

[Legend11]

I just checked my oil and after 1200 miles it is still a quarter of a quarter low (I refilled with a 5 quart container and a refill calls for 5.25quarts). I am relieved that it is not burning/losing oil since I changed it. I am using 5w30 mobile 1 high mileage FUll synthetic. It is still doing the same thing as it was before the oil change so I know the synthetic hasn't caused the issue. I will look into the CD2 detergent. Any other ideas? I recorded it on my iPhone. I will upload to youtube and post