03-27-11, 02:12 PM
Have an 05 STS N* RWD. I have a tapping noise coming from what sounds like the right side of the motor. It is more prominent above the back 2 cylinders. The sound is like tapping the shaft of a screwdriver on a wooden workbench. The noise tends to disappear at times. Can hear it under heavy acceleration and at idle. Especially noticeable at idle when standing by drivers door. The car has 86000 mi and I think it lacked WOT's by the first owner. I am the second owner. Hot or cold the noise is pretty constant. It disappears when accelerating in park in the driveway. Exhaust cams? I got the car for $8000.00 and it is in nice shape
03-27-11, 09:41 PM
First thing I would try is this. Go to auto zone and buy a bottle of sea foam. Dump it in your oil and run it a few hundred miles and then change the oil. It worked on my car, it had what I assume was a sticking lifter ticking, but my car had been sitting for years.
Please don't dump any snake oil in the engine, gas tank or cooling system. See if you can isolate where the noise is coming from. A stethoscope would be a great help.
03-28-11, 05:03 PM
Ranger, I used a stethoscope to find that it was coming from the back right side of the engine. Thanks for takin' time to give me some help. If you have any more help, I'm more than willing to listen. Thanks again
03-28-11, 05:16 PM
"Tapping the shaft of a screwdriver on a wooden workbench" is NOT a good omen. That's an old term for either rod bearing knock or maybe a (static) cam follower lash adjuster that is bleeding down too quickly - grit in the tiny check valve. (I believe your engine still has roller cam follower shoes.)
This an earlier (2000+ FWD) Northstar, but you get the idea.
A rod knock would be low down in the block - valve noise will be up on top of the head.
03-28-11, 07:40 PM
Thanks Sub. My sound description may be a little off. It does not sound like anything to do with a rod. It's not that deep of a noise. It sounds like a lifter tapping in an old Mustang with a 302. Not a great example I know, but the best I can come up with right at the moment. I've prolly owned 7 HT4100's in my days and every one of them knocked. This knock I have now is much lighter and thinner than that famous knock. As I mentioned earlier, load seems to make no difference in this knock. I can hold the brake and give it gas and it does not change. It actually lessens. Hope this helps. I know for a fact that this car has had regular oil changes throughout its life. The car was owned by the owner of the local dealership since it was new. Thanks again, Mike