strange marks on tension arm

[hotrodssnova]

I have some strange marks on my timing belt tension arm. I discovered these marks while i was replacing my alternator. While i was taking the alt off, i discovered that the bolt holding the adjustment arm had broken off. that means, pull the whole side of the engine apart and remove the water pump to get to the broken off bolt. easy enough.
Story continues, I figured while I was in that deep, I would chase down a "rattle" I had at around 2500-3300 rpm. It would have a metallic sound, not quite even with rpm, say around half of, or even 1/3 of rpm. It would not occur under boost, ONLY at low load conditions.
I am looking for opinions. I have excellent oil pressure, new valve train, all bc stuff. The rattle was there when I changed the alt in dec of 2012.
picture of arm:
My theory: the marks are caused by improper adjustment of the tension pulley, causing it to "bounce", and the rattle sound.?????

 

[92AWDHX40]

Do you have a new tensioner?

 

[hotrodssnova]

The tensioner and all the bearings look new. I got the car back in Nov of 2012. It had a complete rebuild before I got it. I just wonder if the tensioning pulley slipped, and caused the tensioner to take up that slack. You can see the 2 distinct marks. The tensioner was definitely out a good bit. Beyond where I would have put it if I had installed it. I am going to replace the tensioner upon re-assembly and a new belt.

 

[Jward5]

I cant believe your belt didnt slip that thing had to have a lot of slack.

 

[pauleyman]

While i was taking the alt off, i discovered that the bolt holding the adjustment arm had broken off

This statement bothers me. How could you even have seen that?

The marks could've come from anytime in the cars life. They aren't shiny so I doubt they are fresh. If you're in doubt put a new tensioner and arm on it and don't worry about it again.

 

[hotrodssnova]

I cant believe your belt didnt slip that thing had to have a lot of slack.

I'm not going to sat it had a lot of slack, but, the adjuster was out a good amount, say...5/16"? Way more then I would accept. I just wonder if that much play would cause a rattle at low loads? I can see at loads going into boost, the belt would, say, pull on the tensioning unit, and not rattle. In a low load situation, I could see it oscillating tight then loose, thus the rattle.....make sense?
Boost will create a nice even pull on the belt and exert pressure on the tensioner, where as a low load, say still in vacuum, will oscillate between push and pull on the belt, and in the tensioning unit. That's what I'm thinking. That's why you see 2 district marks. One for normal boost, and the other for the bouncing around in light throttle.

This statement bothers me. How could you even have seen that?

The marks could've come from anytime in the cars life. They aren't shiny so I doubt they are fresh. If you're in doubt put a new tensioner and arm on it and don't worry about it again.

I noticed the bolt holding the alternator adjuser bracket was broken. Then I had to take the wp off to get to the broken bolt. We all know that in order to take the water pump short bolt out, you need to pull the tensioning pulley assm out. That's when I seen the wear patterns. Not to mention the tensioner was out of adj. Then I thought, AH HA! My rattle! So I posted to get some opinions
BTW, thanks for chiming in. You have helped me in numerous posts you have replied to.

 

[pauleyman]

Guess I missed that part. You were fixing something else and discovered this.

and well...my signature doesn't mean in 24 years old.

 

[hotrodssnova]

Guess I missed that part. You were fixing something else and discovered this.

and well...my signature doesn't mean in 24 years old.

That's some funny $hit.
Yea, complete discovery! I thought the rattle was lifter tick and dismissed it. Then the alt died. Then I found a broken bolt. THEN, I found the tensioner was out of adjustmet. Then I noticed the marks.
So I put 2&2 together and came up with this.
Make sense? Or am I wishful thinking.
This might be the phantom knock I get at around that rpm range. I have it tuned out till I get to 6.5 psi and it runs great, tunerpro, sd

I still would like some educated replies.
Like I said before, all the timing components are in like new condition. The motor was rebuilt just before I took ownership. Oil pressure is 25 at idle, 50-70 at cruise. The rattle only occurs at light throttle, not under boost.
If I were to punch it from a stop, no rattle. Taking off at a light behind another car,...rattle. I think I've found it. Just need more experience on this one.

 

[92AWDHX40]

That's a odd one got a video. Could be anything making that noise.

 

[hotrodssnova]

That's a odd one got a video. Could be anything making that noise.

No videos, and I have explained it thoughly. Its either the tensioner or the oil pump gears. I have run the car without the ps pump, the ac pump, and alt. It has to be the tensioner bouncing when the engine is in vac. Everything is new

 

[pauleyman]

Regardless of what you do sounds like you needed to set the tensioner which you're obviously going to do. If that fails you can take it apart again. Sucks but it isn't life or death. I've had to take it all apart again 5 mins after I finished as have many others. Does suck that you are not 100% sure this is what it is so you're shooting in the dark some. I had a water leak so I knew what I screwed up....but that's another story.

 

[hotrodssnova]

Yea, I've been there too. Perhaps, I'm reading into this too much. It's just I have never seen this wear pattern before. And then the rattle on top of the wear pattern.?
I tuned the crap out of this thing to get rid of the pk at that rpm range, switched tuning programs, pulled spark plugs, blt out the wazoo, you name it........then to find this, well, sorta a relief.
It would be cool if there were a single point of wear in the arm, but, with taking into consideration the newness of the parts, the wear that is observed, it would only come to one conclusion. .....
An improperly adjusted timing belt. The parts are all new, therefore, the wear patterns presented would, in my opinion, would justify the rattle.
Now, unless I have missed something,which I have inspected everything that moves on that side of the car, including: axle bearings, ball joint, muffler bearing, cv joint, brake pads, ac compressor, ps pump, alternator, door hinge, that's the only thing left.
??????