Welcome to the North American Subaru Impreza Owners Club Tuesday August 30, 2016
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo)

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please 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 these ads. 
Reply
 
Thread Tools Display Modes
Old 06-09-2008, 07:14 PM   #1
blitzmr2
Scooby Newbie
 
Member#: 101396
Join Date: Nov 2005
Chapter/Region: Tri-State
Location: East Coast
Vehicle:
2006 WRX
Grip Grey

Default Rod knock on cold start

Today on cold start, there was noticeable knocking from the engine. I turned it off right away, extremely alarmed. It has never done anything like that before.

I checked the oil level, which was spot on, and started it again. The knock disappeared after a few seconds, and never came back. I took it to the dealer, who of course said it was "common." Hmmm--rod knock is common?

I am going to obviously watch/listen carefully, but has this ever happened to anyone here before? It's almost as if the oil pump didn't work right away.

(Oil is synthetic with about 800 miles on it, topped off, new OEM oil filter, stock 2006 WRX)
* Registered users of the site do not see these ads.
blitzmr2 is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 06-09-2008, 07:17 PM   #2
2.5GTLegacy
Scooby Specialist
 
Member#: 111219
Join Date: Mar 2006
Chapter/Region: MAIC
Location: Roanoke, VA
Default

Are you sure it's not the valves? It's pretty common in older subarus where cold weather occurs and oil is not getting up to the heads. Once it warms up...it'll disappear.
2.5GTLegacy is offline   Reply With Quote
Old 06-09-2008, 07:18 PM   #3
ChrisRT
Scooby Specialist
 
Member#: 125941
Join Date: Sep 2006
Chapter/Region: NWIC
Location: Shiatoru
Vehicle:
200x WRX
PSM

Default

It just randomly starts on a random day.


Mine started too. I've read in multiple places that Subaru wanted to save weight in the 1997-2001 generation and shaved the piston skirts on 2.2L engines. I really don't buy that because how much weight is shaving 4 pistons on a 26xxlb car?

Anyway, the pistons supposedly slap around in the chambers until the engine warms up.
ChrisRT is offline   Reply With Quote
Old 06-09-2008, 07:20 PM   #4
mccallrl
Scooby Newbie
 
Member#: 133165
Join Date: Nov 2006
Chapter/Region: MWSOC
Location: Middletown Ohio
Vehicle:
2004 WRX 2.5 hybrid
19t td04 Jr tuned @ P&L

Default

Rod knock sounds a lot different than valve train noise.

Rod knock is a slower louder noise with a noticeable rhythm.

Valve train noise is light and tinny and has a very fast pace, even at idle. You probably have a bit of valve noise, try a thinner oil to help the motor at start up.
mccallrl is offline   Reply With Quote
Old 06-09-2008, 07:23 PM   #5
blitzmr2
Scooby Newbie
 
Member#: 101396
Join Date: Nov 2005
Chapter/Region: Tri-State
Location: East Coast
Vehicle:
2006 WRX
Grip Grey

Default

I appreciate the responses.

I know the EJ25--and Subaru engines in general, are somewhat "noisy." What I heard was *clearly* rod knock. I know valve clatter from piston slap from detonation from a rod knocking due to a lack of lubrication. This was clearly, clearly the latter.

BTW, the car has 23k miles, and has had the oil changed on schedule.

(I said "lack of lubrication.")

Last edited by blitzmr2; 06-09-2008 at 07:29 PM.
blitzmr2 is offline   Reply With Quote
Old 06-09-2008, 07:34 PM   #6
subari87
*** Banned ***
 
Member#: 167422
Join Date: Dec 2007
Chapter/Region: NESIC
Vehicle:
1987 3 main

Default

given the miles, there is not many excuses. My first guess is to think of the softest part, that can fail, to get to oil passages:

The Oil filter.

Just a guess. Take a peak down inside, see if there is a chunk of fibers missing, or ,like old soobs with trochoid oil pumps, the metal that holds the fibre ruptures at 100psi if relief valve doesn't want to kick in. the valve noise sterotyped with subes is pressure relief 9 times out of 10 (else the noise would never go away)...it gets way way too much oil and caves a lifter "out" instead of in. Your new sube may be doing something similar, but at a rod, sure seems like a piece of crud from filter, as crank and rods get first dibs on fresh shot from pump, which is always after the filter...unless it is pressure relieved. Rod knocks do not go away, if they are out of tolerance, they go away, when it has oil enough for the given tolerance (seems simple to type out loud). You got crap in the oil is my guess. I have babbled half a novel here...
subari87 is offline   Reply With Quote
Old 06-09-2008, 07:43 PM   #7
Zornorph
Scooby Specialist
 
Member#: 17332
Join Date: Apr 2002
Chapter/Region: NESIC
Location: The neighbor's yard
Vehicle:
2004 Black STI
Not stock anymore

Default

I doubt it's rod knock - probably piston slap. Very common on subarus.
Zornorph is offline   Reply With Quote
Old 06-10-2008, 02:42 AM   #8
03silvsubie
Scooby Newbie
 
Member#: 158322
Join Date: Sep 2007
Chapter/Region: AKIC
Location: elmendorf anchorage, ak
Vehicle:
03 WRX
PSM

Default

maybe it was just lifter tick :P
03silvsubie is offline   Reply With Quote
Old 06-10-2008, 05:14 PM   #9
blitzmr2
Scooby Newbie
 
Member#: 101396
Join Date: Nov 2005
Chapter/Region: Tri-State
Location: East Coast
Vehicle:
2006 WRX
Grip Grey

Default

You all have convinced me that it's possible it wasn't rod knock, though I have personally witnessed two Toyota 4A-GEs, one 3S-GTE, and my dad's old Lexus ES250 run into the ground, sans oil, and heard the awful, unmistakable sound of rod knock.

Who knows, though. Certainly I'll take piston slap over rod knock any day. I'll keep an eye on it, obviously. Hasn't done it at all before, or since (which makes me wonder why the pistons would slap like crazy on a cold start for 4 seconds, then stop, and not do it anymore).
blitzmr2 is offline   Reply With Quote
Old 06-10-2008, 06:17 PM   #10
flycaster
Scooby Specialist
 
Member#: 60142
Join Date: Apr 2004
Location: Bend, OR
Vehicle:
2011 WRX
Grey

Default

That's the difference - piston slap only occurs on cold start, and then rapidly goes way. Rod bearing problems don't go away, period.
flycaster is offline   Reply With Quote
Old 06-11-2008, 05:30 PM   #11
blitzmr2
Scooby Newbie
 
Member#: 101396
Join Date: Nov 2005
Chapter/Region: Tri-State
Location: East Coast
Vehicle:
2006 WRX
Grip Grey

Default

Quote:
Originally Posted by flycaster View Post
That's the difference - piston slap only occurs on cold start, and then rapidly goes way. Rod bearing problems don't go away, period.
If the engine was run without oil--say, an oil pump not doing its job--then suddenly had an ample supply of oil, would it not knock, then stop knocking (depending on how bad it knocked to begin with)?
blitzmr2 is offline   Reply With Quote
Old 06-11-2008, 08:03 PM   #12
flycaster
Scooby Specialist
 
Member#: 60142
Join Date: Apr 2004
Location: Bend, OR
Vehicle:
2011 WRX
Grey

Default

If it had zero oil pressure with any real rpms and load such that the rod made hard contact with the bearing, it'd be all over. That's an engine killer. That ultra thin oil film is the difference between life and death for a motor.

True rod knock gets worse above 2500 rpms - it'll sound like someone is rythmically slamming a ballpeen hammer against the motor. Once it starts, it won't go away because the bearing has alreasy been fatally damaged causing the clearance to change radically. Here's the bottom line: if you hear noise at startup that goes away once it warms up, you're fine; if you hear loud ugly "banging" noises once it has warmed up, it's time to call a tow truck.
flycaster is offline   Reply With Quote
Old 06-11-2008, 10:07 PM   #13
SUBYDOODIE
Scooby Guru
 
Member#: 71490
Join Date: Sep 2004
Chapter/Region: SCIC
Location: LA/Hollywood
Vehicle:
05 cgm wrx
rubbing axles haha

Default

i have a 2.0 but yea i hear it too... only for a little while in the beginning on cold starts..
SUBYDOODIE is offline   Reply With Quote
Old 06-11-2008, 10:23 PM   #14
ab0z
Scooby Specialist
 
Member#: 126473
Join Date: Sep 2006
Chapter/Region: MWSOC
Location: Grand Rapids, Michigan
Vehicle:
1978 Datsun 280z

Default

Quote:
Originally Posted by blitzmr2 View Post
You all have convinced me that it's possible it wasn't rod knock, though I have personally witnessed two Toyota 4A-GEs, one 3S-GTE, and my dad's old Lexus ES250 run into the ground, sans oil, and heard the awful, unmistakable sound of rod knock.
You should buy these people quarts of engine oil as gifts.
ab0z is offline   Reply With Quote
Old 06-11-2008, 10:29 PM   #15
subaru222
Scooby Guru
 
Member#: 92967
Join Date: Aug 2005
Chapter/Region: SCIC
Location: socal
Vehicle:
2009 wrx hatch
dark grey metallic

Default

subaru222 is offline   Reply With Quote
Old 06-11-2008, 10:39 PM   #16
ringe
Scooby Specialist
 
Member#: 49998
Join Date: Dec 2003
Chapter/Region: RMIC
Vehicle:
2007 WRX CT Stg 2
WRB

Default

Piston slap can sound like rod knock, but it isn't. My car does it too on cold mornings. If it were really rod knock you would soon find out.
ringe is offline   Reply With Quote
Old 06-12-2008, 12:34 AM   #17
flycaster
Scooby Specialist
 
Member#: 60142
Join Date: Apr 2004
Location: Bend, OR
Vehicle:
2011 WRX
Grey

Default

You got that one right. If it's rod knock, break out the running shoes...you'll need 'em to get home.
flycaster is offline   Reply With Quote
Old 06-12-2008, 01:13 AM   #18
Arctic Penguin
Scooby Specialist
 
Member#: 119532
Join Date: Jul 2006
Vehicle:
2006 WRX

Default

sometimes the cam belt tensioner will go bad and cause a noise that for all the world sounds just like rod knock

'deep engine knock' is what it sounds like and isnt
Arctic Penguin is offline   Reply With Quote
Old 06-12-2008, 01:29 AM   #19
fujiillin
Scooby Specialist
 
Member#: 171344
Join Date: Feb 2008
Location: UDel
Vehicle:
2006 STi Wagon
Black HTA Green

Default

+1 for piston slap, I get it occasionally in really cold weather, and it goes right away. Scared the hell out of me the first time it happened.
fujiillin is offline   Reply With Quote
Old 06-19-2008, 10:38 AM   #20
atenzany62
Scooby Specialist
 
Member#: 163172
Join Date: Nov 2007
Chapter/Region: Tri-State
Location: Queens, NYC
Vehicle:
2002 WRX
WRB

Default

Quote:
Originally Posted by fujiillin View Post
+1 for piston slap, I get it occasionally in really cold weather, and it goes right away. Scared the hell out of me the first time it happened.
yea i just noticed it today on cold start, usually i turn on the radio as soon as i turn on the car, but i had the radio off today and i was like wtf is this sound???? so this is pretty normal on all subies i see, and to go with the boxer engine's vibrating too
atenzany62 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
possible piston slap or knock at cold start?? Flyin_Hayn Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 13 12-31-2009 04:57 PM
Knock at cold start shm777 Normally Aspirated Powertrain 13 03-19-2005 06:41 PM
Brake / Clutch Knock Noise on Cold Start -AliasMunky3- Brakes, Steering & Suspension 1 01-25-2005 02:00 PM
Knocking on cold start-up Dm0n3y002 Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 41 01-20-2005 10:56 AM
Knock with cold start jetsiphon Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 3 09-26-2003 12:53 AM

All times are GMT -4. The time now is 11:02 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2016 Axivo Inc.
Copyright ©1999 - 2016, North American Subaru Impreza Owners Club, Inc.