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#2658773 - 06/19/12 02:59 PM interesting paper on piston slap noise
friendly_jacek Offline


Registered: 05/04/03
Posts: 5247
Loc: southeast US
http://dspace.mit.edu/bitstream/handle/1721.1/12156/30012843.pdf?sequence=1

It's an old MIT dissertation paper, but a great source of info. 10W30 weight oil was the best for damping the noise and vibrations, while 5W20 weight was the worst.

This agrees with the epidemic of piston slap in 2006-2010 toyotas when 5W20 oils were implemented.

This also agrees with my experience when piston slap-like noise showed up in my RAV4 when dealer filled it with 5W20 instead of 5W30 that was specified.

Unfortunately, going back to 5W30, 10W30, and now 0W30 GC didn't reverse my noise, so I'm not 100% positive it is a piston slap.

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#2658796 - 06/19/12 03:25 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
INDYMAC Offline


Registered: 07/15/06
Posts: 2330
Loc: Magnolia, TX
I can't open the link, but I've been considering going with 5W-30 instead of 0W-20 in my new 4Runner with the 1GR-FE.
_________________________
2013 Toyota Tundra DC 4X4 5.7L FFV
2012 Toyota 4Runner 2WD SR5
2004 Honda S2000

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#2658810 - 06/19/12 03:34 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
friendly_jacek Offline


Registered: 05/04/03
Posts: 5247
Loc: southeast US
BTW, I just read the "Acnowledgments" (page 4) and it's very hilarious.

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#2659672 - 06/20/12 10:35 AM Re: interesting paper on piston slap noise [Re: friendly_jacek]
Quest Offline


Registered: 12/19/04
Posts: 6347
Loc: beaver land EH?
IMHO piston skirt slap primarily has to do with piston skirt to cylinder wall clearances.

This is dependent on various different things:

-intended clearances on a "run-in" under normal engine operating temperature

-any anomalies introduced during the manufacturing process (wrong selection of piston? excessive machining of the cylinder bore? wrong/excessive clearances due to wrongly selected piston materials (thermal-geometrical expansion properties), etc.

Most of the mass-produced modern engines that suffered from various degree of piston slaps straight from the factory has more to do with manufacturing process and/or the intended design requirements (e.g. GeeAmm had some engines, in the past, with intentionally more piston skirt to bore clearances, straight from the factory, etc.).

uneven wearing of piston skirts would make an otherwise mechanically-sound engine to gradually become noisy (piston slaps) when cold. This is quite prominent as the thermalcycling of alu-alloy pistons thermalcycling over many hundred thousands of miles and gradually losing their proper geo-thermal expension properties.

using higher viscosity oil to "dampen" this piston slapping sound (as opposed to using thinner oil) makes some sense in this case but not the "be all, end all" cure to the problem. For this matter still fundamentally relates to a higher-than-normal "cylinder bore to piston skirt" clearances to begin with.

Bottomline:

(1 ) engines that already suffered from piston slap when cold, try a higher viscosity grade motor oil to dampen the sound.

(2 )engine, over time, will have increased cylinder bore-to-piston(skirt) wear and will experience cold piston slap....again: when that happens, owners can either resort to using the same viscosity grade like before or go slightly higher up if it becomes annoying.


You'll either live with it (the sound), send the engine in for a rebuild (with new/proper piston for proper clearances's sake), or else.

Q.
_________________________
"Internet discussion boards act as echo chambers for conspiracy dittoheads" A.Allen

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#2659723 - 06/20/12 11:15 AM Re: interesting paper on piston slap noise [Re: Quest]
friendly_jacek Offline


Registered: 05/04/03
Posts: 5247
Loc: southeast US
Originally Posted By: Quest


Bottomline:

(1 ) engines that already suffered from piston slap when cold, try a higher viscosity grade motor oil to dampen the sound.


Yes, but the experiments in the paper above showed that 20W50 improved one type of piston slap while made another one worse.

Another variable is base oil (not studied here). There are some anecdotes that esters dampen slap better than PAO, and mineral oil better than PAO: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2658902&page=1

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#2659775 - 06/20/12 12:01 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 14748
Loc: Sunny Florida
We have had quite a few 'slappers' move through here in our GMC fleet trucks.

One is still here at 400k miles. Works every day, no smoke, no oil consumption. I never found anything bad about the slap except a bit of noise. In our trucks they slap for around 30 seconds when cold and then quiet down, sometimes slapping a second or two as they fall back to idle from some higher rpms.

A complete non issue, as the motors apparently are not harmed at all. All our trucks now have fancy coated skirts like I put in my high performance engines.
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"In a democracy, dissent is an act of faith."
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Best ET-12.79 @ 111 mph
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#2659863 - 06/20/12 01:53 PM Re: interesting paper on piston slap noise [Re: SteveSRT8]
friendly_jacek Offline


Registered: 05/04/03
Posts: 5247
Loc: southeast US
Steve,
Your "slap" is different from my "slap".
I have no problems with idle, as the engine is noisy enough while cold to hear any slap. It's the light load at 1500-2000 RPM in the first couple of minutes of driving that produces audible knocking sound, just like pneumatic hammer, but obviously not as loud.

I'm sure it's probably benign, but it was not present in the car in the first 30,000 miles or so, it's clearly abnormal, and I would like it go away.

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#2659910 - 06/20/12 02:34 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 14748
Loc: Sunny Florida
That doesn't sound like piston slap to me.
_________________________
"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix

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#2659942 - 06/20/12 03:17 PM Re: interesting paper on piston slap noise [Re: SteveSRT8]
friendly_jacek Offline


Registered: 05/04/03
Posts: 5247
Loc: southeast US
I know, but this is what Toyota decided to call it now, and it does go away with full warm up, so at least that agrees with a typical piston slap.

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#2660496 - 06/21/12 05:07 AM Re: interesting paper on piston slap noise [Re: friendly_jacek]
INDYMAC Offline


Registered: 07/15/06
Posts: 2330
Loc: Magnolia, TX
Can you post up an audio of what you're dealing with Jacek? Have you been able to eliminate the possibility of valve train noises?
_________________________
2013 Toyota Tundra DC 4X4 5.7L FFV
2012 Toyota 4Runner 2WD SR5
2004 Honda S2000

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#2660727 - 06/21/12 11:14 AM Re: interesting paper on piston slap noise [Re: INDYMAC]
friendly_jacek Offline


Registered: 05/04/03
Posts: 5247
Loc: southeast US
I posted it before here and on RAV4world.

Here you go:




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#2660990 - 06/21/12 04:09 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
INDYMAC Offline


Registered: 07/15/06
Posts: 2330
Loc: Magnolia, TX
No, it's definitely not normal. I just traded a 2009 RAV4 2GR-FE with 43,500 miles and it never sounded anything like yours. I actually considered it to have one of the best engines I've ever owned, and can see why the put it in the new Lotus. I didn't particulary care for the rest of the RAV4 though. That's why we have a new 4Runner. I would unload the vehicle if Toyota can't help you Jacek.
_________________________
2013 Toyota Tundra DC 4X4 5.7L FFV
2012 Toyota 4Runner 2WD SR5
2004 Honda S2000

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#2661070 - 06/21/12 05:23 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
friendly_jacek Offline


Registered: 05/04/03
Posts: 5247
Loc: southeast US
Indymac,

thanks for your comment.

I suspect I would not have the noise if not the screw-up in the dealer where they used 5W20 oil. I argued hard but they defended the infamous Toyota TSB, that could be read different ways, that 5W20 is OK in 2GR-FE. I decided not to change oil to thicker since it was winter time and I was not towing anything. It was a mistake. Sure enough, the noise started at the end of the 5W20 OCI (5000 miles or so).

Actually if you do some research, this noise is very common in camry, lexus, and sienna that specify 5W20 and rare in RAV4 with it's 5W30 specification.

I actually like my RAV4, minus the noises. While Toyota took care of the tranny noise, they didn't budge on the engine noise.

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#2661218 - 06/21/12 07:42 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
HerrStig Offline


Registered: 08/24/11
Posts: 2929
Loc: Boston, MA
Don't rule out a timing belt that has "elongated" or a tensioner which is worn. The 5 series Toyota 4 banger engine is known for some belt noise toward the end the belt life. Sounds awful, goes away with a new belt and tensioner.

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#2661312 - 06/21/12 08:54 PM Re: interesting paper on piston slap noise [Re: friendly_jacek]
Quest Offline


Registered: 12/19/04
Posts: 6347
Loc: beaver land EH?
@OP:

I dealt with piston slaps many times in the past, and yours is definitely not piston slaps. Something is knocking/rapping in there...

Q.
_________________________
"Internet discussion boards act as echo chambers for conspiracy dittoheads" A.Allen

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