Piston Slap??

[ekidd]

Hello all,

I own and LOVE my 2004 Pilot EX. Bought it new in Dec 2003. It currently has 92K miles on it. The only things I've done to it besides normal maintenance was a service bulletin where the dealer added additional fluid to the 2nd gear tranny (I think) which was many many years ago. Other than that, just wipers, lights, battery etc. Absolutely nothing else.

About 3 years ago, when it had somewhere in the upper 60K mile territory, it started a light knocking noise at start-up but would go away when warm. The noise has gotten much worse and now at 92K I refer to it as my diesel. The local dealer and a local engine builder said it is piston slap and that I shouldn't worry about it. It's common in some vehicles and will not hurt anything.

My biggest concern is that we mostly use the Pilot to transport my total care child and her wheel chair. I worry about my wife breaking down and being stranded with our daughter.

And yes I realize that could happen in any vehicle, new or used but I'm big on preventive maintenance! So I'm worried because it is getting louder and louder to the point it is embarrassing if nothing else. It is not using oil so I guess it is a pride thing as I am a Toyota/Honda/Subaru person and often talk about their reliability.

I searched for piston slap but the results didn't yield anything on here.

Has anyone encountered this in the 3.5 engines? Is it normal or just luck of the draw for me? Should I be concerned or at what point should I be concerned? Maybe if it starts using oil?? I plan on keeping it until the wheels fall off because it simply fits me and my family's needs. One of our company vehicles is an 07 Pilot with the 3.5--I think the engines have changed a little over the years but not much and it has around 80K and is as quiet as a mouse. Is it something that could be rebuilt? I guess the cylinder walls could be bored and larger pistons installed but I'm no mechanic. Would it be better to rebuild it or by one for a junker? Can you easily install a newer 3.5 from say and 07 or 08 model???

Any help/thoughts/input would be appreciated. Thanks!

[N_Jay]

Does it go away when warm?
As long as it does, I would not worry at all.

If it does not, then start monitoring for excessive oil consumption or a change in the sound (to more of a hard knock).
As long as oil use is OK, and no hard knocking, sound, I would not worry too much.

[ekidd]

Originally Posted by N_Jay

Does it go away when warm?
As long as it does, I would not worry at all.

If it does not, then start monitoring for excessive oil consumption or a change in the sound (to more of a hard knock).
As long as oil use is OK, and no hard knocking, sound, I would not worry too much.

It used to go away when warm but now you can hear it all the time. It's much louder when cold, especially if you start it up, wait a few seconds, put it in gear and put it under a light load like pulling out or backing up.
Even when I get to work, after driving 25 miles and put it in neutral, you can still hear a knocking, just not as deeply as when it's cold. I had thought about trading up to a newer model but it's paid for and I just can't bring myself to giving someone else my problem. I just can't do it.

If it's possible, I'd like to find a newer model 3.5 with low mileage and swap it out. I'm just not sure if all the wiring harnesses etc are compatible.

[ekidd]

After doing a little more googling, I found something interesting in not only the Honda/Acura 3.5L engines but also Toyota's 3.5L engines and piston slap as well as all brands of autos. I
thought piston slap was the piston rocking in the bore but someone mentioned short piston skirts being the culprit.

A comment was that it could also be due to short piston skirts. In a combustion engine, the pistons are sealed inside of the cylinder walls by the piston rings. The rings, as they are called, are making contact with the cylinder wall while the piston rides up and down, centered by the rings in the cylinder wall. At the top and bottom of each stroke, as the piston is changing direction, the piston rocks. It is then that the piston skirt makes contact with the cylinder wall, setting the piston straight once again to continue its journey.

Depending on the stroke of the crankshaft and the length of the connecting rod, the piston skirt could be making contact with the crankshaft at the very bottom of its travel or stroke causing the piston slap sound.

Does any of this make sense?

[N_Jay]

I doubt the piston is touching the crank.. It the piston skirt "slapping" the walls of the cylinder.

[robs]

Have you replaced the timing belt yet? If not that could be the sound of the hydraulic adjuster piston hitting the the adjuster pulley. The oil in those things wear out over time and sounds like a rod knock.

A guy in another thread pulled the timing cover and was able to get the belt to wiggle by pushing on it with his hand. It should not do this

[ekidd]

Originally Posted by robs

Have you replaced the timing belt yet? If not that could be the sound of the hydraulic adjuster piston hitting the the adjuster pulley. The oil in those things wear out over time and sounds like a rod knock.

A guy in another thread pulled the timing cover and was able to get the belt to wiggle by pushing on it with his hand. It should not do this

No, the timing belt has not been replaced. I was waiting until the 105K mark but if I knew for sure that was the issue, it would be a no brainer. I'll drop by my local Honda dealership and ask them if they think it could be the belt.

Thanks!

[robs]

Try this. First thing in the morning let it warm up for a few minutes. Then rev the heck out of the motor. Floor it to try to bring it to at least 6k. Listen for it and see if at some specific rpm the noise completely goes away.

[ekidd]

The knocking goes away completely between 2,500 and 3,000 rpms and stayed that way up to nearly 6K.

I'm curious, what does that mean??

[robs]

Originally Posted by ekidd

The knocking goes away completely between 2,500 and 3,000 rpms and stayed that way up to nearly 6K.

I'm curious, what does that mean??

It means the hydraulic tensioner adjuster is shot.

Here is the actual part
More Information for BECK/ARNLEY 0241439

The oil has lost it's viscosity and cannot hold the piston tight to the pulley. When you rev it, the rotational force of the belt puts enough pressure on the pulley to sink it all the way in and get the two pieces to stop banging together.

See the complete kit for a better visual
More Information for AISIN TKH001

It's the two bottom pieces that are banging together

Have the timing belt done and make sure to replace *ALL* hardware along with the belt.

good luck.

[ekidd]

Originally Posted by robs

It means the hydraulic tensioner adjuster is shot.

Here is the actual part
More Information for BECK/ARNLEY 0241439

The oil has lost it's viscosity and cannot hold the piston tight to the pulley. When you rev it, the rotational force of the belt puts enough pressure on the pulley to sink it all the way in and get the two pieces to stop banging together.

See the complete kit for a better visual
More Information for AISIN TKH001

It's the two bottom pieces that are banging together

Have the timing belt done and make sure to replace *ALL* hardware along with the belt.

good luck.

Thank you for the information!!!

If I buy the Complete Kit linked above, that will cover ALL hardware?

[robs]

Yes but I just posted the kit with the best picture. You may want to shop around

[goneb4u]

mt pilot does the same thing, changed t-belt and tensioner last fall, same sound, don't be surprised if the sound remains in fact I would bet on it, these tensioners rarely fail.

[vanduker]

Valve adjustment?

I would do the timing belt and tensioner just as a maintenance item and based on age so maybe that will do it but I would look at the valve adjustment as well.

The belt is not that bad of a job to do yourself. I have not done the valve adjustment as ours is still quiet but that job also looks not too tough.

[vanduker]

Valve adjustment?

I would do the timing belt and tensioner just as a maintenance item and based on age so maybe that will do it but I would look at the valve adjustment as well.

The belt is not that bad of a job to do yourself. I have not done the valve adjustment as ours is still quiet but that job also looks not too tough.