cold start rod knock

[mike06train]

I have a rod knock for around 3 minutes at cold starting. The oils pressure gose up and I get a knock until it warms up.Then, the oil pressure returns to normal and the knock gose away. It's a 2007 Denali and aside from that runs perfect. Looking for ideas for a reason before I see if the factory powertrain warranty will cover it. Knock sensor maybe? Any info would be a big help.

 

[murdr'd HOE]

im guessing you have a 5.3. I had a 2000 with the 5.3 a 2008 with the 5.3 and now an 09 with the 5.3 and they all tap a little from a cold start. Its not a rod knock its a lifter tap. As soon as the oil pumps it up it goes away. I started using synthetic in my 2008 and it stopped the tap. Good luck !

 

[02Lightning]

Did it start doing this after an oil change? How maney miles? Sounds like it might be a sticky lifter.

 

[thumper_ehhhhh]

I only had the lifter tap when i use castrol oil. Bad decision to try something other than what i regularly use. Quaker state no lifter tap.

 

[mike06train]

I should have given more info. I have a 2007 Denali with the 6.2 motor. Milage is high due to long highway trips. It sounds more like a knock then a lifter tap. Its a heavy deep noise like someone is tapping the side of the block with a hammer. It's pretty loud. I've run motors with mechanical cams and some with hot hydroloic cams that would the lifters would need some time to pump up. It's not that kind of noise. The other day it did it bad enough that the check engine light came on. I just would like to get some ideas before I take it to the dealer.

 

[doubletapdrew]

There was a problem very similar to what you are describing, called piston slap. I hadn't heard of the more recent engines being affected by that though, just the previous body style trucks/suvs.

 

[thumper_ehhhhh]

Dont know if this will help but I found this. http://www.ls1tech.com/affiliates/truck/forums/showthread.php?t=364389

 

[OklabyGodhoma]

I'll offer this in hopes that it will help you. First off the sound you are hearing if I am reading you correctly is pretty normal. It doesn't usually last as long as you describe but I have a couple of things for you to try.

First off get 2 cans of Chemtool B-12, liquid not spray. Wait until you are almost empty on fuel and when you go to fill up put both cans in first then fill your gas tank; also find 100% gasoline with NO ethenol. Second change your oil and go with a pure synthetic. I personally use only Mobile 1 and have in all my vehicles for the last 20+ years. I also only use WIX filters due to the higher volume of filter material.

The Chemtool will clean your system and ensure that none of your problems are caused by pre-detonation (not a normal problem but it does happen). I use it in all my vehicles about every 5th tank just to keep the system clean. For normal use I only use 1 can per 20 gallons of fuel. The synthetic oil has far too many qualities for me to go into here but just know that it's far, far superior to any fossil fuel oil. My NORMAL oil change interval is 10,000 miles. I advise paying attention to the recommendations of your vehicle taking into account mileage and tempreture range you will be operating under and adjust accordingly. If you are making the switch to synthetic I suggest you run the first oil change only 4,000 miles and change oil and filter. Then you can increase intervals between changes.

Hope this helps with your problem; give it about 3,000 miles after you make the changes before deciding if this cured your problem or not. Just for info, I'm a retired Quality Assurance/Safety Manager for a military base motorpool.