Engine noise is driving me up the wall!

[trainguy1989]

My 3.2L engine makes a very subtle knock when started in the cold and goes away when the car warms up. It won't knock at all if its 60F or above out. I was just told it is the rod bearings making noise until they warm up. I have new rod bearings, but do not have the time to do them until spring as I have no garage, its very very cold, and leaves and dirt are blowing around. As the oil warms up and thins out, a rod knock would get louder, not the other way around, right? Would this more likely be a valvetrain noise then? This noise was even around before I did my 60K. I used a screwdriver on various parts of the engine(timing covers, valve covers, etc), but cannot pinpoint the noise. I have been trying to diagnose this myself, but I am stumped. Any help is greatly appreciated!!!!

Thanks,
David

P.S. Heres a video:
[youtube]nxonoe75QCk[/youtube]

 

[rubydist]

I'm going to guess that you are hearing a piston slap because the rings are sticky. When it warms up, the piston expands enough that the rings fit better and the noise goes away. I can't hear well enough on the audio to tell what's going on, but that is a common issue on these engines, especially if the previous owners didn't like to change the oil, or if they have sat for extended periods of time. AutoRx or Seafoam has helped on occasion, and Mobil 1 has lots of detergents so it helps clean up that stuff over time.

 

[trainguy1989]

When I did my 60K valve adjustment the car was as clean as a whistle. The previous owner was using mobile 1. The noise is the loudest around 0:17 sec.

Thanks

 

[Ishodu]

Take a quick min to check to see if the crank bolt is loose. 19mm socket.

 

[trainguy1989]

went to turn the crank bolt. When I cranked on it it turned the accessories.

 

[badcamelot]

noise

Just a thought but have you check the exhaust system? I realize this my be strange considering that it isnt there when above 60, but if it gets cold enough perhaps part of the exhaust cools easier than another and then when warm it holds together better. I had an old truck whose manifold kinda did this. Probably not it, but a thought. I listened to the video too and couldnt hear any specific knock. Perhaps on your video you could say -right after the knock "there that was it' - still to provide video was awesome.
Good luck.

 

[jmpSHO]

It sounds like a rod knock to me but it's hard to say listening to a video on my computer.

 

[trainguy1989]

If it was a rod knock, why would the noise disappear when it warms up. A rod knock would get louder when the oil thins out, right? The knock cab be heard best at 0:17 and 0:34 sec

Thanks for all your help guys!!

 

[ShadetreeSHOguy]

That sound is either a rod knock, crank cancer to me..

 

[trainguy1989]

 

[SHOtimer]

Have you inspected your timing chain tensioners, a lot of times those can cause similar noises.

Doug

 

[trainguy1989]

The timing belt seems quite tight. If the tensioner was going bad, how could I tell other than the noise? Would the belt be lose? If it were crank cancer, would it make sense for the knock to go away after the car has warmed up? Is it possible for a rod knock to go away with after the engine warmed up? As mentioned above, would piston slap make this sound?

This is quite mind boggling to me. So thanks for all your guys input!

David

 

[jonheese]

Timing chain tensioners, not timing belt.

You should remember them from the valve adjustment portion of the 60k, they are little springy pads that push up/down on the timing chains between the intake and exhaust cams on each head to keep them tight. As the plastic pads wear down over time, slack is introduced in the timing chains, and can cause a knocky kind of sound as the slack is taken up and payed out many times per revolution.

Regards,
Jon Heese

 

[tps761]

^^^^ what he said. had this happen to me in my mustang. thought it was a bad lifter, turned out it was a worn tensioner alowing slack.

 

[trainguy1989]

When I put the screw driver on the valve covers no noise is coming from them. when I did my 60k the chains were tight and the pad had quite a bit of wear left.

Just sounds like it is deeper in the engine....
It just does not make any noise what so ever if it is above 60 F.
This is just weird.....:banghd:

Thanks, guys
David

 

[1993MTXSHO]

It's hard to tell from the vid, but what octane fuel do you run? My 94 will do this when I run 87 but go away if I run higher grade fuel. Once it warms up its fine but it's when the engine's cold that it gets ******.

 

[trainguy1989]

I have been running 91 octane. The knock seems to be louder on the rear bank(by firewall) which is about 0:17 sec in the vid

 

[RonJohn]

I'm going to guess that you are hearing a piston slap because the rings are sticky. When it warms up, the piston expands enough that the rings fit better and the noise goes away. I can't hear well enough on the audio to tell what's going on, but that is a common issue on these engines, especially if the previous owners didn't like to change the oil, or if they have sat for extended periods of time. AutoRx or Seafoam has helped on occasion, and Mobil 1 has lots of detergents so it helps clean up that stuff over time.

forged piston when cold will also make a knocking sound till warm then they expand.. thats what it sounds like to me..

 

[Brett]

My car knocks slightly upon start up and goes away. occasionally coming up here and there but goes away with some revs, for me its the rod bearings. I know this because my dad did them when he got some cabin fever while i was at work, and didnt pay much attention to the torque specs. I'm not saying it is the problem, im saying dont rule it out because it only does it when cold. did you do rod bearings when you did the 60k? previous owner do them?

 

[trainguy1989]

I have not done them and as far as I know the PO did not do them.