Could this be exhaust leak? - Toyota RAV4 Forums
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#1 (permalink) Old 11-27-2012, 11:53 PM
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Could this be exhaust leak?

As some of you might remember I have this weird knocking engine noise under acceleration on cold engine. Started almost 2 years ago and I posted about it before.

" title="engine knock in Toyota 2GR-FE engine cont. - YouTube" target="_blank">engine knock in Toyota 2GR-FE engine cont. - YouTube

Someone on Youtube suggested to look for exhaust leak. The more I read about it, the more it fits, especially the cold engine part and acceleration only.

Anyone had a small leak that sounded like that? This is news to me.
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#2 (permalink) Old 11-28-2012, 01:54 AM
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serpentine belt tensioner pulley ??????????????????????
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#3 (permalink) Old 11-28-2012, 09:21 AM
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I listened several times and honestly it is hard to tell with the background noise.

My initial impression is piston slap on a cold engine. I have experienced this on 4 different GMs over the years so I do have an ear for it (although the piston slap sound sometimes sounds different in different vehicles and engines).

I have had manifold leaks in different vehicles and I am not quite getting that feeling, but again it is very hard to tell without being there in person.

When you say a cold engine, how long before the sound goes away? I found piston slap would disappear after a few minutes of driving under a light load. An exhaust leak will sometimes result in a loss of MPG.

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#4 (permalink) Old 11-28-2012, 11:21 AM
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Originally Posted by Noel View Post
serpentine belt tensioner pulley ??????????????????????
When I had a tensioner problem in my corolla, it sounded differently and it wasn't cold engine only either.
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#5 (permalink) Old 11-28-2012, 11:26 AM
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I listened several times and honestly it is hard to tell with the background noise.

My initial impression is piston slap on a cold engine. I have experienced this on 4 different GMs over the years so I do have an ear for it (although the piston slap sound sometimes sounds different in different vehicles and engines).

I have had manifold leaks in different vehicles and I am not quite getting that feeling, but again it is very hard to tell without being there in person.

When you say a cold engine, how long before the sound goes away? I found piston slap would disappear after a few minutes of driving under a light load. An exhaust leak will sometimes result in a loss of MPG.
Well, for a long time I did think it was a piston slap. Some Toyota people also called that. What is different in this compared to GM piston slap, no dieseling in idle, but only on acceleration. No correlation with ambient temp meaning you can hear it in summer as well as winter. It does go away with hot engine. 2 miles of driving or so.
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#6 (permalink) Old 11-28-2012, 12:08 PM
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Hard to tell from the video - but that does sound a lot like piston slap or even rod knock. Especially when it gets louder with off-idle speeds (accelerating) and when the engine is cold. Does it do this when you are in park/neutral? Or only under load?

There are a number of other possibilities that might cause that sort of noise - from a cracked flexplate/transaxle issue (loose bolt making contact with engine side) to worn suspension parts (powertrain was binding).

Exhaust leak is a possibility, but to me, that would sound a little bit different. If you notice a change in exhaust tone if you drive through a puddle, that might put more weight toward an exhaust leak. I have a fairly decent exhaust leak on the Corolla - doesn't quite make the same sound as yours, just sounds like a louder exhaust.

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#7 (permalink) Old 11-28-2012, 12:10 PM
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Could be a bad sensor triggering early firing thus detonation in one cylinder. What sensor is driven by heat measurement?
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#8 (permalink) Old 11-29-2012, 10:14 AM
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Originally Posted by fishexpo101 View Post
Hard to tell from the video - but that does sound a lot like piston slap or even rod knock. Especially when it gets louder with off-idle speeds (accelerating) and when the engine is cold. Does it do this when you are in park/neutral? Or only under load?

There are a number of other possibilities that might cause that sort of noise - from a cracked flexplate/transaxle issue (loose bolt making contact with engine side) to worn suspension parts (powertrain was binding).

Exhaust leak is a possibility, but to me, that would sound a little bit different. If you notice a change in exhaust tone if you drive through a puddle, that might put more weight toward an exhaust leak. I have a fairly decent exhaust leak on the Corolla - doesn't quite make the same sound as yours, just sounds like a louder exhaust.
Fishexpo,
thanks for your expert comments. I just tried revving in park. The noise is very faint and you can only hear near 2000 RPM when fast idling. It's mostly noticeable under load. The thing is I live at the bottom of a hill and have to accelerate moderately to keep at 25 MPG in the first mile of driving. If my commute was different, I would probably never notice the noise. But, my other cars don't do it and RAV4 didn't do it either when new, so I know it's abnormal.
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