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'03 Spec V, 148k miles, original owner for over 17 years now. Just replaced the rocker cover gasket (for the second time) and noticed what sounds kind of like a bunch of marbles being thrown around under the rocker cover. All tools and screws accounted for, so there shouldn't have been anything left in the engine. It's hard to tell if it's an air, electrical, or mechanical sound, very random and constant, not synchronized with the spark plugs or injectors. Engine idles and accelerates fine. Engine does bog down a bit when the fans/AC kick on, still trying to figure out the source of that. Thinking it's a marginal aftermarket alternator I'm going to replace soon. Previously replaced the radiator fans already. New battery ground cable on order too.
The PCV hose was hard as a rock and I thought it might be leaking so I replaced that. I thought it could be a bad ignition coil (been through that twice) thinking maybe one was arcing internally so I replaced all four and it still sounds the same. If I put my ear right over the engine while idling it seems to be loudest just over cylinder 2 and 3 ignition coils. Felt around the oil tube gaskets and can't feel any leaking. Oil level is correct. Just had the upper oil pan off to replace the leaky seal and didn't see any timing chain issues.
Maybe the sound was always there and I just didn't notice, but it seems like something I would have noticed given the volume. The engine cover does a decent job of quieting it down, but I've been under the hood plenty of times with this car and this just seems different.
Not super concerned because it runs smooth. I might just pull the cover off again just to see if there's anything obvious. Looking for other ideas.
 

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Do you have an aftermarket valve cover (doesn't have the "NISSAN" logo on it). Sometimes at the 4th cylinder area, the cams hit the cheap valve cover and breaks pieces off of it.
 

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Yeah it's aftermarket (after the first gasket replacement because the spark plug tubes were full of oil). This time I took the aftermarket cover off and just replaced the gasket. While it was off I looked inside and didn't see anything that appeared to be damaged. Had been running with this cover for at least a year now. Definitely sounds like some random piece of material getting knocked around in there though.
I'll do an idle relearn and if it's not gone probably just take the cover back off and double-check this weekend. It's a pretty quick task and the cover gasket is brand new so it should be OK using it again.
 

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Eric the car guy shows this about the aftermarket valve covers. Right around 45 minute mark. Anyway it doesn’t sound like that’s your problem though. Yea the only thing to do is to pop that vc off and take a look. Isolate it while it’s running so you know where to zone in when you remove the vc. Good luck.


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Do you have an aftermarket valve cover (doesn't have the "NISSAN" logo on it). Sometimes at the 4th cylinder area, the cams hit the cheap valve cover and breaks pieces off of it.
That stupid as shit and I didnt know that, but I believe it. There is no faith in anything after market!

Maybe its new to you because you noticed it after you did the job? I would pull it and get an oem valve cover. The tube seals are not serviceable even tho some kits sell them. Check for impact marks on the old vc. But really it sounds to me there is too much valve lash between cam and bucket. Replace and see what happens.
 

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Discussion Starter #7
Well I took the cover off and found nothing unusual. Everything still held in place, no busted/cracked parts, nothing hiding in the engine. Mine doesn't sound like anything Eric was experiencing - that's a very regular sound based on timing. Mine just sounds like things randomly bouncing/flowing around.
After I put the cover back on and trying to narrow it down more the engine reached full temp and all of a sudden it got quieter, then the cooling fans kicked on about 30 seconds later. Maybe it's coolant flow? Coolant pump? Still weird to me that it's loudest right over the two middle coil packs. I recently replaced both thermostats, which also required a coolant flush. It definitely isn't overheating, gauge goes to just below mid-level like it always has and stays there.
I haven't bothered to let it cool down and see if it comes back. It idles, revs up, accelerates, and drives fine.
Regarding the bogging down, turns out I had a crappy aftermarket alternator. I had proactively replaced the alternator about 2 years ago. This weekend I swapped back the original one, did a battery ground cable swap, and cleaned the remaining dirty terminals (positive at battery and the ground wire near the alternator). Now it idles like a champ and barely changes the rev level when fans and AC cut in. Also feels like I gained some HP back.
Have to agree on the POS aftermarket parts, at least for critical parts like the alternator. Maybe I got lucky with my rocker cover, but might dump that for OEM in the future too.
 

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Is it loudest when start up? or is it constant.

I had a very loud chain slapping which was my Cam Phaser and possibly worn chain tensioner but it was mostly only on start up.

I just did all the timing components and the rattle went away, if its the same noise you are hearing.
 
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