a 6ya Mechanic can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repair professionals here in the US. click here to Talk to a Mechanic (only for users in the US for now) and get all the help you need. Goodluck!
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
The 3.4L engine has special pistons that are designed to expand as the engine heats up. When the engine is cold, the pistons make a knocking sound that resembles lifter noise or piston slap. As long as the noise goes away after the engine warms up, don't sweat it; this is normal.
Sounds like excess bearing clearance, when the engine sits overnight the oil between the bearings and the crankshaft is able to run back into the oil pan. When you first start it up it takes a few seconds for the oil pump to fill the spaces back up and you get some clatter.
Hard to say over the internet but I will try to explain. If the noise is a distict KNOCK KNOCK and it sounds like it is coming from the bottom of the engine, then it most likely is a rod or main bearing. If it is a TAP TAP noise that sounds like it's coming from the top of the engine, then most likely a valve lifer is failing/failed.
the fact that it goes away when the car is warm, makes me lean towards a bad lifter. Normaly if a bearing is bad and knocking, the noise doesn't go away.
The KNOCK noise will be somewhat hollow sounding and the TAP TAP sound will be more solid. If the KNOCK KNOCK is solid, then a rod or main bearing has most likely failed to the point that a new/reman engine will be needed.
If the knock goes away after it warms up there are 3 possible causes for this: 1. The pistons are slapping meaning there is piston or engine wear. 2. There is carbon on the top of the pistons. This is the most likely cause. GM says this is not detrimental to the engine. 3. The o-ring between the oil pump screen and the oil pump may be cracked causing areation of the oil. This one was supposed to be there from the time the engine was new but I have seen the problem appear at 50k miles. The oil pan will have to come off to replace the o-ring.
the most common issue is what is called piston slap, GM's official stance is that it will not cause any long term damage, in other words it is just annoying, my Corvette has the same noise, goes away in about 2 miles, had it to the dealer and that is what they said, and i agree with them because it has never gotten any worse after years or hard use/.