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2005 Z: Help requested: Engine knocking at idle ONLY WITH A/C ON
**SEE ATTACHED VIDEO**
Hey guys, I literally just bought this 2005 350Z and once I got it home I noticed it knocking at idle.
It will only do this “knocking” after it’s been driven a while, and only when the A/C fan is on. It can knock as loud as it wants, but as soon as I put the A/C to the off position, it stops. The knocking also stops whenever gas is applied to the vehicle.
I've also noticed the static of the radio at fluctuating volumes. No issues with power steering though.
See the attached video! Looking for any suggestions or anyone that has experienced the same/similar issue! Thanks in advance!
Last edited by vndr09; Jul 4, 2018 at 09:40 AM.
Reason: Problem narrowed down, so post updated!
Based on what you said that it only happens when the clutch is not engaged, I'd suspect it to be part something with the clutch, flywheel, bad install or a combination. If the engine was knocking that loud, I'd imagine you wouldn't be making much power that you would notice it. It also seems to be associated with heat expansion since it only occurs after you've driven it. Or possibly something with the fan or shroud?
I've blown a motor before and it was knocking with or without the clutch being engaged. Oil was coming out of the exhaust port when I took the header off. It drove like crap and was obvious.
Doesn't sound great, but we need more information. Oil pressure? oil level? It goes away when driving?
Oil pressure and levels are good. It occurs after it’s been driven for a while. Or just driven. In other words, when the engine is warm.
Originally Posted by K20Z350
Based on what you said that it only happens when the clutch is not engaged, I'd suspect it to be part something with the clutch, flywheel, bad install or a combination. If the engine was knocking that loud, I'd imagine you wouldn't be making much power that you would notice it. It also seems to be associated with heat expansion since it only occurs after you've driven it. Or possibly something with the fan or shroud?
I've blown a motor before and it was knocking with or without the clutch being engaged. Oil was coming out of the exhaust port when I took the header off. It drove like crap and was obvious.
Gotcha, okay, well that makes me feel better. That’s what I was leaning towards too; or at least something non-engine related.
any idea on how I can check those things myself? Or is that something to take to a mechanic?
Gotcha, okay, well that makes me feel better. That’s what I was leaning towards too; or at least something non-engine related.
any idea on how I can check those things myself? Or is that something to take to a mechanic?
If you are unsure then take it somewhere. I know many wouldn't agree with me but I'd take it to a Nissan dealership. They usually charge 30-100 to diagnose the problem. If not, go to somewhere that specializes in Nissan.
I must of overlooked the clutch part. If the clutch pedal is out then TOB. If clutch is pressed then pilot bearing. Could be something else wrong in there, but sounds like engine is fine, but you're going to have to drop the tranny
Gotta ask the obvious question: what brand and grade of fuel have you been using? Since there was no knocking for the previous owner and on your test drives, something changed and you need to figure out what it was.
I must of overlooked the clutch part. If the clutch pedal is out then TOB. If clutch is pressed then pilot bearing. Could be something else wrong in there, but sounds like engine is fine, but you're going to have to drop the tranny
The clutch pedal is both in and out. It happens at idle and in neutral. Whether the clutch pedal is depressed or not does not make a difference. Does this make sense?
Originally Posted by dkmura
Gotta ask the obvious question: what brand and grade of fuel have you been using? Since there was no knocking for the previous owner and on your test drives, something changed and you need to figure out what it was.
It happened after I drove the car home from the seller to my garage. Same day I purchased it. But, I did stop on the way home and I put 91 (premium) octane in the car, per the fuel cap instructions.
Like everyone is saying though, since it happens at idle, and only at idle, with the clutch disengaged, it can't really be the engine, can it?
My Z Has An Engine Knock Only At Idle, When I’m Stopped And It Progressively Gets Worse When The Engine Gets Warmer. It Sounds Exactly Like Yours. It Started Happening After I Changed Aftermarket Valve Covers To OEM Cuz Aftermarket Was Leaking.
I Don’t Know If This Relates But I Also Have An Oil Leak Somewhere Driver Side Mid Engine. It’s Not The Valve Covers But It’s Somewhere A Little Lower.
This Is Below Under The Valve Cover Next To A Radiator Hose Connecting Into The Engine
I Can’t Upload A Video Of The Sound Atm
Last edited by Andrewu24; Mar 9, 2022 at 11:10 PM.
My Z Has An Engine Knock Only At Idle, When I’m Stopped And It Progressively Gets Worse When The Engine Gets Warmer. It Sounds Exactly Like Yours. It Started Happening After I Changed Aftermarket Valve Covers To OEM Cuz Aftermarket Was Leaking.
I Don’t Know If This Relates But I Also Have An Oil Leak Somewhere Driver Side Mid Engine. It’s Not The Valve Covers But It’s Somewhere A Little Lower.
This Is Below Under The Valve Cover Next To A Radiator Hose Connecting Into The Engine
I Can’t Upload A Video Of The Sound Atm
This Is The Only Video Atm
Last edited by Andrewu24; Mar 9, 2022 at 11:11 PM.
2005 Z: Help requested: Engine knocking at idle ONLY WITH A/C ON
