FZXtreme

Hello All,
Recently my S has started to make a strange noise upon start up. At first I thought that maybe my clutch was going but deduced that that is not the case since the sound persists without engaging the clutch. I've researched it and looked through a bunch of videos and can find a sound that matches mine so I made my own and was hoping someone more knowledgeable than me may be able to pin point the origin of the sound.
https://www.youtube.com/watch?v=8-an...ature=youtu.be
The sound does seem to originate from the engine bay area but I haven't had the time to fully investigate it but I'm guessing it may be something loose rattling around or something seriously damaged.
The most recent work that I have done to the car is a radiator swap and a valve adjustment, if this information may be relevant, for a track day two weeks ago. The car has been sitting since that track day since I cracked a rotor and haven't had the time to fix it and the sound first happened a week after that event while I had to move the car.
Any input would be greatly appreciated and thanks for looking.

windhund116

Maybe pulley or idler going out. Take off accessory belt and start car --- for a moment. See if noise goes away.

Good luck!

Soviet

Does it continue as you rev? Does it disappear when warm?

It is a bit strange that the sound pattern is non deterministic.

Car Analogy

Good suggestion. Easy to check using that idea.

Another possibility, sounds like something loose that is banging around with engine vibes. Like broken exhaust hanger, letting pipes bang against chassis. Grab exhaust at tail tip, and try to move it around forcefully. See if hear it hit anything. Better to try that under car, grab pipe in the middle someplace, move it around. But at tip takes zero work.

If its not that, I would try under hood, put pressure on stuff with engine running, see if noise goes away. Stuff like intake box, battery heat shield, etc. Just use your gloved hand.

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FZXtreme

If I recall correctly it does not continue as I rev and it does happen when the car is warmed up which leads me to believe that it could just be something rattling about. I will confirm this info when I work on the car this weekend, car is stored 10 miles from my location and schedule wont allow me to stop by and verify.

I was thinking of the battery heat shield as well since I had to remove it to do the valve adjustment, maybe forgot to tighten it down properly... I will attempt your suggestions first and report back with my findings.

Will try this last if the previous ideas don't work.

Thank you guys/gals for the tips.

FZXtreme

Alright, update time.
So I was finally able to look into this noise some more and may have discovered a more severe issue in the process...yay... but first ill address the issue at hand.
The noise does happen when the car is warmed up but the noise does not get louder/continue as I rev the engine. It does seem to happen when the revs drop back down to idle and if I rev it to 1500 rpm and hold it the noise is constant but only at 1500 rpm.
I tried to shake random parts of the car to see if anything is loose but have not found anything to be the cause, the exhaust, heat shield, I shook almost everything and nothing was the cause.
I still cant seem to determine if it's coming from the front of the engine or the rear, as the sound just seems to originate from the engine overall.
I still havent taken off the accessory belt to see if it's the pulley but will try that sometime during the week and report back.
I also decided to remove the valve cover since I did a valve adjustment recently and considered a retainer upgrade and removed the cams so I wanted to double check the torque on all of the screws and that the cams are aligned properly. I believe they are but will post a pic to have others verify.

I have an ingalls torque damper installed which partially obstructs the view but I believe that it still shows enough to determine if it's aligned.
I also took pictures of the spark plugs for shits and giggles and will post to see if maybe they show something someone may see a problematic.




Now onto the other issue I discovered. I decided to do a compression check, again for shits and giggles, but did it without warming the engine up as I've read that a cold compression test my just show lower numbers but what I have seen was worrisome. My numbers for 3 trials of each cylinder for the cold test were as follows:
Cyl1:
215
212
215
Cyl2:
140
155
160
Cyl3:
200
200
200
Cyl4:
215
215
215
So the results are that something is seriously wrong with cylinder 2 and cylinder 3 is a bit low so decided to do another test after warming the engine up and the results are as follow:
Cyl1:
220
225
222
Cyl2:
220
220
221
Cyl3:
208
205
205
Cyl4:
222
225
225
Now cylinder 2 is back up to par with 1 and 4 but 3 is still a bit lower than the rest. Should I be concerned with this or should I be fine and just keep monitoring it to see if it worsens? I have a track day coming up next weekend and concerned about abusing the car given this information so any help or advice is greatly appreciated.
Thanks!

Car Analogy

Did you test them in sequence, 1, 2, 3, 4, both times? What getting at is did battery get low, and maybe the low cyl was the last one you tested both times, as batt was getting low (and testing it warm meant battery must have gotten rechaeged a bit between tests). Low batt would obviously result in low reading.

Cause otherwise its seriously weird to have one low cyl, but a different low cyl, onw test to the next.

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FZXtreme

I did it in 1,2,3,4 sequence both times. Then I went again for the cylinders that were low so for the cold one I did 1,2,3,4,2 again and warm 1,2,3,4,3 again.

Car Analogy

Ok, then its seriously weird. One low cyl each time, but a different low cyl on different tests? Test A, cyl 2 low, but 3 ok. Test B cyl 2 now fine but now 3 is low???

Maybe the gauge connection is flaky, and sometimes leaks air. Maybe it just so happened to not be connected well to cyl 2 on test A, then cyl 3 on test B.

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FZXtreme

In both tests cyl3 seems to be around the same numbers, but cyl2 has a drastic change. My main concerns are if such a change from cold-hot tests could have such a change in compression like the case with cyl2. Then if cyl3 being about 15psi lower than the rest consistently is a major issue.