What are the symptoms of a cracked piston ring? - Subaru Impreza WRX STI Forums: IWSTI.com
STI Forum
Join
STI Products
Start New Thread Create Account Advertise FAQ Members List Contact
Go Back   STI Forums > IWSTI Engine & Drivetrain > 2.5 Liter/Litre Factory Motor > What are the symptoms of a cracked piston ring?
Welcome to IWSTI - The world's largest Subaru Impreza WRX STI forum!
Welcome to the IWSTI.com Subaru Impreza WRX STI forum.

You are currently viewing IWSTI.com as a guest, which limits your ability to access discussions, ask technical questions, and learn more about the Subaru Impreza WRX STi models. Join for free today and unlock full access to post topics, communicate privately with other members (PM), respond to polls, share content, and access many other special features. Join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see this welcome message.
Like Tree1Likes

Reply
 
Thread Tools
Old 12-15-08, 11:24 AM   #1
Developing Advanced Mastery
Feedback Score: 1 reviews
 
Fav Mod: Buddy
My Threads
Posts: 994
My Subaru Parts for sale

Join Date: Feb 2008
Location: NJ
pisymbol is an unknown quantity at this point
Default What are the symptoms of a cracked piston ring?

How do you tell? Should there be smoke? People talk about a rough idle, is that all the time or can the car still idle properly in some instances. Any CEL's thrown?

pisymbol is offline   Reply With Quote
Old 12-15-08, 11:31 AM   #2
Advanced Contributor Level 4
Feedback Score: 2 reviews
 
Car: E90 BMW 335xi
My Threads
Posts: 472
My Subaru Parts for sale

Join Date: Sep 2007
Location: Denver, CO
roninsoldier83 is an unknown quantity at this point
Send a message via Yahoo to roninsoldier83
Default Re: What are the symptoms of a cracked piston ring?

On my former WRX, cracked my #4 ringland. For reference, it was a fairly minor crack, so car still had pretty good idle, was a little low on power, but actually even that wasn't too noticeable. No noticeable white smoke either. Compression test revealed #4 about 50psi low.

Anyway, I received a flashing CEL, with cylinder #4 misfire code. Although I pretty much knew something was likely damaged after I heard audible detonation under 20psi of boost, as my FPR hose slipped off under full boost. Shortly after I started receiving the flashing CEL letting me know there was a misfire on #4.
__________________
E90 BMW 335xi 6MT- Titanium Silver Metallic
roninsoldier83 is offline   Reply With Quote
Old 12-15-08, 12:00 PM   #3
Platinum Member
Feedback Score: 0 reviews
 
Car: 08 DGM STI
Fav Mod: My wife :)
My Subaru Parts for sale

Join Date: Oct 2003
Location: Ontario, Canada
Digitalfiend is an unknown quantity at this point
Default Re: What are the symptoms of a cracked piston ring?

Quote:
Originally Posted by roninsoldier83 View Post
as my FPR hose slipped off under full boost.
Damn, how does that happen (assume FPR is fuel pressure regulator)?
__________________
2008 Dark Grey Metallic STI
Mods: Stage 1 94 Custom tune | Kartboy f/r shifter & TiC pivot bushings | StopTech SS brakelines | Whiteline 24mm adj. front and 22mm adj. rear swaybars & front brace | RCE springs | Cosworth oil control baffle | STI competition engine & tranny mounts | NGK 1-step colder plugs | Group-A pitchstop mount & front/rear endlinks | MadDad EL header

2009 DGM WRX265 (wife's car)
SOLD - 2005 Aspen White STi
Digitalfiend is offline   Reply With Quote
Old 12-15-08, 12:05 PM   #4
Advanced Contributor Level 3
Feedback Score: 8 reviews
 
Car: WRB 06 Sti
Fav Mod: Piss on evo sticker
My Threads
Posts: 349
My Subaru Parts for sale

Join Date: Aug 2006
Location: Tri-State
santacruz02 is on a distinguished road
Send a message via AIM to santacruz02
Default Re: What are the symptoms of a cracked piston ring?

On my last motor I cracked 3 of 4 ring landings. Rough idle, smoke on start up and smoke while under mid to high acceleration. Check your oil level. Mine was only found by a leak down test, as it was not the compression side but it affected the oil ring. Hope this helps.
santacruz02 is offline   Reply With Quote
Old 12-15-08, 12:14 PM   #5
Developing Advanced Mastery
Feedback Score: 1 reviews
 
Fav Mod: Buddy
My Threads
Posts: 994
My Subaru Parts for sale

Join Date: Feb 2008
Location: NJ
pisymbol is an unknown quantity at this point
Default Re: What are the symptoms of a cracked piston ring?

Can you guys define rough idle? Was that all the time or only during a cold start? Did the idle move up and down constantly or just sit at the wrong RPM range?

Finally, how drivable was the car with a cracked ring?
pisymbol is offline   Reply With Quote
Old 12-15-08, 12:37 PM   #6
Becoming A Master Contributor
Feedback Score: 12 reviews
 
Car: 08 AW STI - 10/31/08
Fav Mod: P & L 30r :)
My Threads
Posts: 624
My Subaru Parts for sale

Join Date: Sep 2008
Location: Houston, TX
combatp21 is an unknown quantity at this point
Default Re: What are the symptoms of a cracked piston ring?

Quote:
Originally Posted by santacruz02 View Post
On my last motor I cracked 3 of 4 ring landings. Rough idle, smoke on start up and smoke while under mid to high acceleration. Check your oil level. Mine was only found by a leak down test, as it was not the compression side but it affected the oil ring. Hope this helps.
What does a leak down test involve?
combatp21 is offline   Reply With Quote
Old 12-15-08, 12:52 PM   #7
Advanced Contributor Level 3
Feedback Score: 8 reviews
 
Car: WRB 06 Sti
Fav Mod: Piss on evo sticker
My Threads
Posts: 349
My Subaru Parts for sale

Join Date: Aug 2006
Location: Tri-State
santacruz02 is on a distinguished road
Send a message via AIM to santacruz02
Default Re: What are the symptoms of a cracked piston ring?

Quote:
Originally Posted by combatp21 View Post
What does a leak down test involve?
I did not perform the test, my local subaru dealer did. Corret me if i am wrong but I thought it was similar to a compression test but there is another needle that moves back down to 0 as compression is lost.
So the car is turned over then I assume he watched the gauge.

as far as rough idle, my car was shaking could have been a little low on the rpms but I don't recall. and yes it smoked everytime.
I don't know your setup, but at stage 2 there is alot of blow by causing oil to get into the intake plumbing and intercooler, this too can cause a smokey start up I think.
idk if bent valves can cause that but im sure thats something else you wnana check into. either way, do one of the two tests. should reveal some info for ya.
santacruz02 is offline   Reply With Quote
Old 12-15-08, 01:00 PM   #8
Master Contributor Level 2
Feedback Score: 1 reviews
 
Fav Mod: black
My Threads
Posts: 853
My Subaru Parts for sale

Join Date: Jul 2008
Location: norcal
leeroix is an unknown quantity at this point
Default Re: What are the symptoms of a cracked piston ring?

LEAKDOWN TEST= Differential cyllinder pressure test. with pistons at top dead center, compressed air is pumped into the combustion chamber via the spark plug hole. a guage on the regulator lets you know how much air is being lost to ring blow by, or burnt or other valve damage, (intake or exhaust) usually this test goes hand in hand with a compression test and lets you pinpoint any internal damage.
leeroix is offline   Reply With Quote
Old 12-15-08, 01:31 PM   #9
HowTo Contributor
Feedback Score: 7 reviews
 
Fav Mod: 10.85 at 129.43
My Subaru Parts for sale

Join Date: Mar 2006
Location: 9.55 at 146mph
jasv11 is on a distinguished road
Default Re: What are the symptoms of a cracked piston ring?

I cracked the ringland between the top 2 rings of piston #2. No smoke No burnt oil,no noises, I just lost power,went from running 114 mph at the strip to running 108mph and did a compresssion test and was down to 70lbs in # 2
__________________

motor&tuned by www.innovativetuning.com
jasv11 is offline   Reply With Quote
Old 12-15-08, 02:28 PM   #10
Developing Advanced Mastery
Feedback Score: 1 reviews
 
Fav Mod: Buddy
My Threads
Posts: 994
My Subaru Parts for sale

Join Date: Feb 2008
Location: NJ
pisymbol is an unknown quantity at this point
Default Re: What are the symptoms of a cracked piston ring?

Quote:
Originally Posted by jasv11 View Post
I cracked the ringland between the top 2 rings of piston #2. No smoke No burnt oil,no noises, I just lost power,went from running 114 mph at the strip to running 108mph and did a compresssion test and was down to 70lbs in # 2
Wow that sucks. Did you have even a "rough" idle?

The other question I have is can a cracked ring cause the engine to just shut off during driving?

Last edited by pisymbol; 12-15-08 at 02:33 PM.
pisymbol is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help? More

All times are GMT -8. The time now is 08:21 AM.


Powered by vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Designed & Powered by Domain Architect
Privacy Policy