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Discussion Starter #1
Hi- I have a '11 Pilot LX 4x4 with 120k miles. There's a knocking sound coming from the top left side of the engine (near the top pulley), as well as slight grinding noise. When in Park and the engine is revved the knocking gets louder obviously, but then stops around 3000 RPMs. Let off the gas and the RPMs drop back down, the knocking/grinding starts up again. While driving the sound is heard the same way, at idle at a stop, then louder as it revs and gets up to speed, then stops around 3000RPM, but theres no loss of power, just an annoying sound that doesn't sound good at all. Oil changed a month ago and no issue until today.


Before dropping it off at the dealer would like to see if anyone has experience with this issue or know what it could be. Thanks
 

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Since you say (near the top pulley), I assume you mean from the top left side of the engine when standing in front of the car. Best guess is that its a water pump (because of the knocking). Have you had the complete TB change with WP yet? But there are a lot of pulleys and wheels on bearings there that could be making the noise, so it cold be anything. Probably not the engine itself though..
 

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Might be the alternator. Bad front bearing can be noisy. My alternator failed a couple of months ago, and I thought it was the power steering pump at first. Grinding and rattling could be the alternator.
 

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Discussion Starter #4
Timing Belt Tensioner - found issue

Yes, as you look at the engine, the sound was top left. Happens to be the Timing Belt Tensioner, which now is recommended to also replace water pump/timing belt even though they are still good. Glad it wasn't anything more serious, like in the engine itself. When you hear knocking and grinding you think the worst. Any one else out there who has experienced this best to get everything done at once per Honda recommendations. More expensive right now, but will save time in the long run not to go back when those issues do and most likely will arise. hope this thread can help some else out.


Since you say (near the top pulley), I assume you mean from the top left side of the engine when standing in front of the car. Best guess is that its a water pump (because of the knocking). Have you had the complete TB change with WP yet? But there are a lot of pulleys and wheels on bearings there that could be making the noise, so it cold be anything. Probably not the engine itself though..
 

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Yes, as you look at the engine, the sound was top left. Happens to be the Timing Belt Tensioner, which now is recommended to also replace water pump/timing belt even though they are still good. Glad it wasn't anything more serious, like in the engine itself. When you hear knocking and grinding you think the worst. Any one else out there who has experienced this best to get everything done at once per Honda recommendations. More expensive right now, but will save time in the long run not to go back when those issues do and most likely will arise. hope this thread can help some else out.

How did you confirm it was the timing belt tensioner and not the drive belt (accessory) tensioner? I have a similar issue but I'm almost certain it's the accessory tensioner as I've seen several videos posted that match the sound (in those videos replacing the accessory tensioner resolved the issue).



The bolt to relieve tension on my accessory tensioner is nearly stripped from me using a 12 point socket last time I replaced my alternator, so its due for a replacement anyway even if that turns out to not be the cause of the noise.
 

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Have the same knocking noise during cold startup only. Bought car to honda dealer and it was the timing belt tensioner 100%. Had to do a complete timing belt kit replacing at 74k. Sound is now gone. Told dealer to save the old hydraulic tensioner to see and it was bad. There was some play to the tensioner piston. It would pushback a little when i tested it. Seems like alot of honda pilots have this common issue and its never a recall.
 

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Have the same knocking noise during cold startup only. Bought car to honda dealer and it was the timing belt tensioner 100%. Had to do a complete timing belt kit replacing at 74k. Sound is now gone. Told dealer to save the old hydraulic tensioner to see and it was bad. There was some play to the tensioner piston. It would pushback a little when i tested it. Seems like alot of honda pilots have this common issue and its never a recall.
recalls are usually mandated by the government and include the safety of the driver/passengers.


Its common for the tensioner to lose tensioner and cause a rattle
 

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120K on your original timing belt? You got lucky it was just the tensioner. There have been posts here where the tensioner fails and the belt jumps a cog or two. My original tensioner was leaking at 105K when I did my first timing belt service. The replacement failed 70K later and I ended up just replacing the tensioner. The noise came back here at 185K and after replacing the tensioner again (this time with Honda tensioner) the noise did not go away. The noise on mine did not present itself until you were lightly accelerating or just letting off the gas. Sounded fine under load or at idle. I decided to just do the timing belt service early since the replacement tensioner was still good. The belt was a bit stretched, pulleys all spun freely without noise. Replaced water pump, timing belt, pulleys, TB tensioner, accessory belt tensioner and accessory drive belt. Now we are nice and quiet. My first TB service was done using a Gates TB kit. This one I used Aisin. I still have the plugs to do at 200K to complete the TB service.
 

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How did you confirm it was the timing belt tensioner and not the drive belt (accessory) tensioner? I have a similar issue but I'm almost certain it's the accessory tensioner as I've seen several videos posted that match the sound (in those videos replacing the accessory tensioner resolved the issue).

The bolt to relieve tension on my accessory tensioner is nearly stripped from me using a 12 point socket last time I replaced my alternator, so its due for a replacement anyway even if that turns out to not be the cause of the noise.

I just wanted to post an update. It turns out it was my timing belt tensioner after all. I removed the serpentine/accessory belt yet the noise was still present. Compared to my new one, the old part leaked all the hydraulic fluid and was significantly lighter. I installed the new one and all is good.
 
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