Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

Piston Slap / Rod Knock ?


  • Please log in to reply
25 replies to this topic

#1 fishy

fishy

    USMB is life!

  • Members
  • 255 posts
  • Nova Scotia, Canada

Posted 27 February 2013 - 02:59 PM

Hey gang,

   Help me diagnose this one if you can, please.

Here's a video of my 98 ej22 making a racket. I'm hoping for piston slap because I don't believe that to be fatal...

Facts that I know:
1. The noise gets quieter as the car warms up but never completely goes away.
2. The colder the morning the louder the startup
3. I have no knowledge of the car ever being overheated but I've only owned it for about 14,000kms (forgot to say: the car is currently at about 235,000kms)
4. It does have oil in it.



Edited by fishy, 27 February 2013 - 03:23 PM.


#2 gbhrps

gbhrps

    User Awaiting Email Confirmation

  • Members
  • 786 posts
  • canada

Posted 27 February 2013 - 03:13 PM

fishy,

 

Its been many years and three newer OBW's since I had my 97 OBW LTD, that did the same thing as yours. At around 23 000 km it developed this same symptom under the exact same conditions. Owned the car until 2004 and 279 000 km later and never had an issue with the motor, or with the car for that matter.

 

I can't say if yours sounds the same as the one I had (too many years ago) but my wife and I just lived with the issue until we traded cars. Any research I did at the time suggested that piston slap was an annoyance only, and had no effect on engine longevity.

 

If your noise is piston slap, it shouldn't be a problem for you. There is no need to worry. Good Luck!



#3 ShawnW

ShawnW

    Subaru Master Technician

  • Administrator
  • 12,891 posts
  • Denver, Colorado

Posted 27 February 2013 - 04:47 PM

Rod knock always gets worse as the engine runs for a longer period of time in my experience.  I don't like piston slap and make great strides to eliminate it in all the engines I rebuild but I never pull one out of a car because it does it-always recommend to the customer that they live with it.  I know of one customer with 50,000 miles of slapping and no other problems with the motor.  I am amazed these don't at a minimum consume oil a little bit but the ones I have worked with didn't even do that.



#4 The Dude

The Dude

    Certified Subaru Nut

  • Members
  • 798 posts
  • South Carolina

Posted 27 February 2013 - 05:15 PM

I owned a 1999 Forester and it had piston slap for the entire 200,000 miles that I owned it. The engine was noisy, especially when cold, but it never used a drop of oil. Overall, it was a great car and probably had at least another 100,000 miles of life left when I sold it.



#5 Hakim Craddock

Hakim Craddock

    Member

  • Members
  • PipPip
  • 22 posts
  • N Plainfield, NJ

Posted 27 February 2013 - 06:53 PM

i have read somewhere that rotella t shell diesel oil helps quiet down the piston slap... My 03 forester sounds similar (173k miles) but not quite as loud, and it comepletely goes away ounce it is fully warmed up. I dont know what oil is in there  now because i just got the car and it has another 2k left b4 an oil change is needed.. But i think i am going to try a 10-40 synthetic oil in there unless someone in here advises against it.



#6 djmark7

djmark7

    USMB is life!

  • Members
  • 230 posts
  • NW New Jersey

Posted 28 February 2013 - 08:13 AM

same here '98 leg 2.2, goes away completely when warmed up 140k on motor



#7 grossgary

grossgary

    Elite Master of the Subaru

  • Members
  • 19,339 posts
  • WV

Posted 28 February 2013 - 12:48 PM

i think the timing tensioner is slapping around - pull the drivers side timing cover (3 10mm bolts i think).  get a light and watch the thing flop around.  you can run the engine without timing covers to see.  it'll be notably bouncing all over the place. 

 

interference engine - so you need to replace it like yesterday. 

ebay kits are the way to go - all new tensioner, pulleys, and belts for reasonable prices.

 

or it's piston slap, it's benign but just annoying, turn the radio up and ignore it. 

 

 

doesn't seem like rod knock - like Shawn says Subaru rod knock seems to get progressively worse.  if you're driven 14,000km without it changing that doesn't seem like rod knock to me. and rod knock doesn't diminish as it warms up....and that motor is not prone to rod knock like the EJ25 of the same era....lots of things in your favor here.


Edited by grossgary, 28 February 2013 - 12:49 PM.


#8 chaz345

chaz345

    New User

  • Members
  • PipPipPip
  • 94 posts
  • Portland, OR

Posted 28 February 2013 - 06:46 PM

The way you describe it, worse when the engine is cold, sounds like piston slap but I'm not an experienced expert on the matter. Everything I've heard though suggests that if it were rod knock, your engine would have blowed up by now. They don't tend to last thousands of miles with knocking rod.

#9 uniberp

uniberp

    mpergielwalkermi

  • Members
  • 626 posts
  • Walker, MI

Posted 01 March 2013 - 07:00 AM

Hey gang,

   Help me diagnose this one if you can, please.

Here's a video of my 98 ej22 making a racket. I'm hoping for piston slap because I don't believe that to be fatal...

Facts that I know:
1. The noise gets quieter as the car warms up but never completely goes away.
2. The colder the morning the louder the startup
3. I have no knowledge of the car ever being overheated but I've only owned it for about 14,000kms (forgot to say: the car is currently at about 235,000kms)
4. It does have oil in it.


 

If it is a recent and rapid development it is rod knock. "Be prepared" is my advice.



#10 WoodsWagon

WoodsWagon

    Formerly 91Loyale

  • Members
  • 3,931 posts
  • NH

Posted 01 March 2013 - 11:23 PM

The rev and release you did at 1:45 in the video would have resulted in a nasty back-rattle noise if the rod bearings were gone.

 

It does sound a lot like piston slap but that doesn't start suddenly.

 

As Grossgary mentioned, the timing belt tensioner is a known culprit of bad noises. If you take the drivers side cover off you can peer in with it running and see if the tensioner is flapping about or holding steady.

 

The other possibility is a cracked flexplate if it has an automatic transmission.



#11 fishy

fishy

    USMB is life!

  • Members
  • 255 posts
  • Nova Scotia, Canada

Posted 02 March 2013 - 07:44 AM

Thanks for the input, guys.

When I think harder about it I guess the noise hasn't exactly started suddenly. This car sat in my garage being worked on over last winter and when I finally fired it up in the spring to get it on the road it was knocky then too. I think a combination of exhaust leak and warm weather kept the knock from being noticable for a while. This fall I got the exhaust patched up and then the temperatures started to drop. We've had a pretty cold winter here so maybe it IS just a really horny case of piston slap. Here's hoping.

I broke off one of the 10mm inspection cover bolts the other day trying to get in there for a peek. I'll have to try the other two when I get a chance again. If I break them all off at least I'll be able to take the cover off! I could always goop the cover back on with a few blobs of RTV or something I suppose.

I'm curious what a cracked flexplate does to the operation and longevity of the engine/car. Does anyone have experience with those?



#12 Fairtax4me

Fairtax4me

    Su bah roo'n

  • Gold Subscribers
  • 7,884 posts
  • Charlottesburg, VA

Posted 02 March 2013 - 09:27 AM

IMG_1646.jpg
A cracked flex plate usually makes a metallic rattly banging noise. It's going to be most prevalent when the engine is put under load at low RPM, such as when shifting into drive or reverse.
A circumferential crack (shown above) can make a hell of a racket and leave you dead in the water if the flex plate separates entirely. If the center section breaks out the engine power doesn't get transferred to the transmission, and you go nowhere. Also once that happens, after the engine is stopped it will not restart because the flex plate is used to turn the crankshaft for starting. The starter will engage and the flex plate will spin, but the engine will sit still or may jump randomly.
Radial cracks (from the center out) can be fine for quite a long time, and may not even make noise in some cases.

Typically they cause no internal damage to the engine or transmission, but anything is possible with the right combination of failure and luck. (Or bad luck)

Edited by Fairtax4me, 02 March 2013 - 09:31 AM.


#13 grossgary

grossgary

    Elite Master of the Subaru

  • Members
  • 19,339 posts
  • WV

Posted 02 March 2013 - 10:32 AM


I broke off one of the 10mm inspection cover bolts the other day trying to get in there for a peek. I'll have to try the other two when I get a chance again. If I break them all off at least I'll be able to take the cover off! I could always goop the cover back on with a few blobs of RTV or something I suppose.

I'm curious what a cracked flexplate does to the operation and longevity of the engine/car. Does anyone have experience with those?

 

use zipties to hold the cover on, easily removed the next time. or leave it off or concoct something, not a big deal.  if the tensioner fails then you'll end up with bent valves, so i'd check that first.  2 bolts stand between you and avoiding a huge engine repair.

 

if it's not that and it's piston slap then you can ignore it the rest of your life.

 

i wouldn't worry about a flexplate, that's probably the least likely cause.  well covered by fairtax...hopefully he didn't learn that all by experience!!!...it's just a plate between the engine and trans so it's benign in terms of "longevity of the engine car", it'll just leave you stranded eventually. I've never heard of any damage from one, but like he said with bad luck, i wouldn't necessarily want to see a worst case scenario.



#14 ivans imports

ivans imports

    1000+ Super USER!

  • Members
  • 2,902 posts
  • lumby bc canada

Posted 02 March 2013 - 10:37 AM

totaly piston slap its fine have had lots thiss bad i fix thiss all the time i whould remove #2 #4 pistons and knurll them and reinstall and noise will be gone the late model 2.2 were bad for thiss as the pistons are very short and the oil ring supply holes get pluged and wears the top side of piston badly. I fix thiss alot when i do 2.5 headgaskets surface the heads and knurll #2#4 some engines sound realy bad. If it was a rod it whould be shaking and not smooth when reved and it whould get louder when warm have you put a oil preshure gauge on it ? no less than 10 psi hot at idle i'.m shure its fine



#15 fishy

fishy

    USMB is life!

  • Members
  • 255 posts
  • Nova Scotia, Canada

Posted 07 March 2013 - 05:09 PM

Hey guys, minor update:

The slap/knock continues...

 

I checked the timing belt tensioner and could NOT see it jumping around anywhere.


I also changed the oil (due anyway) and put in some Castrol(I think it was) "High Mileage Engines" type stuff that I saw on sale. That seems to have made zero improvement(as expected). I couldn't see any silver/gold flake in the old oil so I take that as a sign that there wasn't.



#16 ivans imports

ivans imports

    1000+ Super USER!

  • Members
  • 2,902 posts
  • lumby bc canada

Posted 08 March 2013 - 10:43 AM

Have had many with bad piston slap lately is fairly commen on the 98and up engines the only problem it seems to cause is theknock senser backs off the timing. Nothing will fix it without tearing the piston out and ether replace it or knurll it



#17 torxxx

torxxx

    I void warranties

  • Members
  • 2,914 posts
  • Fairbanks

Posted 08 March 2013 - 11:35 AM

+1 for piston slap

 

I'm wondering if you got whats technically a 99 2.2L block?  98 on back were not prone to piston slap.  Yours sounds just like my mom's 01 Legacy, and shes driven it for 40k+ miles with that same noise.  Dealer verified it was piston slap and said drive it.

 

Its a subaru engine anyways, they were meant to be driven til a rod plays peekaboo out the top center of the block :P



#18 uniberp

uniberp

    mpergielwalkermi

  • Members
  • 626 posts
  • Walker, MI

Posted 08 March 2013 - 06:41 PM

+1 for piston slap

 

I'm wondering if you got whats technically a 99 2.2L block?  98 on back were not prone to piston slap.  Yours sounds just like my mom's 01 Legacy, and shes driven it for 40k+ miles with that same noise.  Dealer verified it was piston slap and said drive it.

 

Its a subaru engine anyways, they were meant to be driven til a rod plays peekaboo out the top center of the block :P

But then you lose the core value.



#19 Prwa101

Prwa101

    Subaru Fanatic!

  • Members
  • 581 posts
  • Sandy, OR

Posted 08 March 2013 - 09:18 PM

Just a though, I had a similar problem on my forester, it started all of a sudden. Felt like something broke and ran really bad. Pulled the timming covers off, tired out the timming sprocket bearing went out, bent the bolt and all 20 degrees. Start with the simplest work you way up.

Good luck!
-Prwa

#20 mikec03

mikec03

    USMB is life!

  • Members
  • 276 posts
  • greenfield, wi

Posted 09 March 2013 - 09:44 AM

Sounds like the piston slap on my 97 2.2 legacy.  I've put 30K on it since it started.  

 

+1 to the jipties. 



#21 ivans imports

ivans imports

    1000+ Super USER!

  • Members
  • 2,902 posts
  • lumby bc canada

Posted 09 March 2013 - 10:13 AM

if you look at the top of block in the middle front it has four letters aa-bb this indacates the bore on the cly the b bore has more piston slap problems than the a bore check if its b bore on #2#4 if so that whould be the slap



#22 fishy

fishy

    USMB is life!

  • Members
  • 255 posts
  • Nova Scotia, Canada

Posted 15 March 2013 - 08:53 AM

if you look at the top of block in the middle front it has four letters aa-bb this indacates the bore on the cly the b bore has more piston slap problems than the a bore check if its b bore on #2#4 if so that whould be the slap


I'm not sure where those numbers are. Do I need to have anything removed to find them? 

Car is still slapping and rattling along down the road. I estimate at least several thousand kilometers since the noise has gotten on my nerves.



#23 ivans imports

ivans imports

    1000+ Super USER!

  • Members
  • 2,902 posts
  • lumby bc canada

Posted 15 March 2013 - 09:44 AM

top center behind the alt on the flat part of block



#24 chaz345

chaz345

    New User

  • Members
  • PipPipPip
  • 94 posts
  • Portland, OR

Posted 15 March 2013 - 11:21 AM

I'm not sure where those numbers are. Do I need to have anything removed to find them? 

Car is still slapping and rattling along down the road. I estimate at least several thousand kilometers since the noise has gotten on my nerves.

The noise, if it's piston slap, is definitely completely harmelss. My mechanic's shop loaner does it to the point that at idle it sounds like a Volkswagen diesel. Get's some very strage looks from other Subie people at stoplights.

#25 ivans imports

ivans imports

    1000+ Super USER!

  • Members
  • 2,902 posts
  • lumby bc canada

Posted 16 March 2013 - 09:08 AM

i could knurll a piston and send it to you need to know the bore is it a-b but it will last like that






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users