GTS4 RB20 clunks while shutting off?

[SkylineP]

Hey everyone, over the last week my gts4 rb20det has developed this sound. It doesn’t always happen but after turning the key off it will kinda clunk in the last movements of the engine, also when that does happen sometimes when I start it back up it will be like a one clunk before it fires completely up, the car runs and idles fun, just sometimes has that weird clunky feeling while shutting off. It was also kinda shaking at lights while idling. Car is stock besides a hks bov that vents to the air. 

[GTSBoy]

You may be best off trying to video this and find the best spot to put the camera/mic for us to hear it. And if you're going to go to that effort, you might end up putting the camera/mic in odd places, like on the ground next to the gearbox to see if the noise is coming from down there.

[SkylineP]

I’ll try, it’s hard because it doesn’t do it all the time.

[SkylineP]

• Okay here is a video taken from under the car. It’s like towards the end, the couple clunks, also there has always been this squirting\electric noise that I’ve never been able to pinpoint after ever shut off.. that is the very last sound you’ll hear after the clunky sound. Sorry first video didn’t load; second one should work.. 

Edited September 25, 2019 by SkylineP

[GTSBoy]

Dunno. Sounds like mine shutting off. The "clunk" is not really a clunk. It sounds like gearbox rollover noise coming to a stop.

The hiss is also normal, and in they all do it. The options are;

• Air leaking in to a volume that is under vacuum (ie brake booster, or plenum chamber) through a small leak. The IACV would qualify as such a small leak into the plenum that would perhaps make that sound and you only hear it because all the other noise suddenly stops.
• Fuel flowing away through the reg as it closes up when demand from the injectors suddenly stops.
• Other such similar crap.

[SkylineP]

Thanks for the response!

Okay, sometimes it’s a bit more predominate with the clunk feel and sound, that has been the first one I could even catch the car doing it because it’s definitely not all the time, maybe one shut off out of ten?  I was first thinking it’s just the internals coming to a stop but for the two years I’ve had it I don’t e er remember that feeling or sound and it’s not all the time. Also noticed tonight at idle while I was eating fast food in a parking lot that the engine would have sudden slight jerks, very small but I could feel it in the cabin.. would assume that’s either spark or fuel?

[SkylineP]

Also would the gearbox even be turning at all if the car is in neutral and at idle?

[SkylineP]

Here’s another one I just got from under the car.

[GTSBoy]

31 minutes ago, SkylineP said:

Also would the gearbox even be turning at all if the car is in neutral and at idle?

Yes. Input shaft is driven by the clutch whenever the clutch is engaged. Neutral just means that there's nothing meshed to the input shaft.

My R33 box makes a truly enormous amount of rollover noise. Clutch in at idle and the background noise level drops appreciably.

[GTSBoy]

26 minutes ago, SkylineP said:

Here’s another one I just got from under the car.

I like the crickets at the end. Very fitting.

I don't think I would be worrying about your noise.

[SkylineP]

Okay so this noise seems to be getting worse and am dreading taking it into a mechanic because 1: it's hard to find a trustworthy mechanic and 2: it's a skyline in the US and everyone will have a "skyline markup" for any work done. 

The noise only happens when I've been driving for a while on highway or kinda pushing it. It also sometimes feels "clunky" when starting it up, but mostly the "clunk-clunk-clunk" happens right after the car is shut off. I've tried shutting off with clutch pushed in and also in gear with clutch pushed in while shutting off but nothing seems to make it sound better or eliminate it. Someone besides gtsboy has to have some input about what this could be, because it's not sounding normal now. Thank you for any help!!

[KiwiRS4T]

Sorry can't hear it from here.