My 2004 I35 has 167,000 mi. Just started with an engine tapping when engine is warm. It does not tap when engine is cold. I tied Seafoam for gunk in oil. I've tried an oil additive stabilizer. Still taps. Any ideas?

It has developed a clicking engine noise on a cold start. After the car has warmed up, the sound goes away. ... Clicking or a sharp tapping from the valve cover on top of the engine would point to a valve train noise. A dull tapping or slapping sound from the side of the engine block would point more toward piston slap.4 Nov 2011

Cold-start engine clicking is a nuisance, not a disaster - StarTribune.com

tap usually associated with lifters when vehicle warms up oil thins out and a bad or worn lifter will make a tapping noise --other oil level low --oil needs changing --low level will starve rockers/push rods/and lifters which will also cause tap ---damaged /dirty{sludge oil can cause same problems

A tapping noise that starts out cold and goes away when warm is usually caused by a valve lifter inside the engine. The lifter may be worn/leaking down and will be noisy until it fills with oil pressure. You can try an oil additive ( Lucas Oil Additive ) available at most part stores works very well with noisy lifters. Another noise that can happen cold and go away when warm is an exhaust manifold leak. However, this is normally a ticking type sound rather than a tapping sound.

I've had the same problem. I think that begin with the weather started getting cold but I can't say for sure. I am definitely going to check the hose.

Are you absolutely certain the noise is lifter tap and not an exhaust leak? These are pretty well known for breaking exhaust manifold studs, or even cracking exhaust manifolds. The noise will be present on a cold engine but might go away as the engine heats up and the manifold expands. Maybe that's why it seems to go away after adding additives or changing the oil. It gets just enough heat in the engine to fool you in to thinking the issue was resolved by adding the oil/additive. Are you always adding to a cold engine?

-Rod

sorry scrap it

try draining the oil and putting kerosene in the engine, then run the engine for a minute and drain, this will clean out a lot of gunked up debris in your motor, when you refill the oil put some conditioner in with it like Lukas or Risloan. You may have to do this a few times in a short period to get the system all cleaned out.

try changing the oil but use seafoam in the oil first and run it for a while,the lifters may be dirty and this may fix them,ive heard this sound in a 2004 f150 before but havent tried anything yet

lash adjuster broke or need to primed. All rocker arms can be fine and you will hear a sewing machine noise to a tapping/knocking depending on severity or how many are failing. However a lead tech would check these I imagine and the car is so new, I wonder if it was not broken in and abused while brand new. Also never let it sit in the cold to prevent dry starting where the oil is thick and not lubricating properly. Can you give details as to what they have check or stated they have checked?

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Try changing to an heaver oil first,if your using 10-30 go to 10-40,see if this helps,before looking at the valves.