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FB25 CHATTER....concerned...

21K views 43 replies 23 participants last post by  JoDa 
#1 ·
i know this has been talked and discussed about before, but my 08/15 built ob has it. were talking about two secs of chatter from somewhere in the valvetrain. whether this is caused by the upside down oil filter(probably not) or just a bad timing chain tensioner design or something else is a little worrisome. take it to the dealer you say? 99.99% probability from them saying it's normal nothing to worry about. what i would like to know is do any members here with the fb25 claim they DO NOT hear this chatter or have this issue. really love this 5th gen ob, but it's a little worrisome on the longevity of it. i just never ever had a vehicle with this chatter.
 
#2 ·
test drive a few in their parking lot and see if they do it - if it's just at start up then you don't even need a test drive - just start it up.

you could always trade it in for one that doesn't - be a negligible loss for having the piece of mind.
 
#3 ·
First off, you use 0w-20 is not like the EJ which use 5w-30, thinner oil at startup more chance of chatter until oil is flowing and lubricating at normal operating temperature. It is good practice to give the FB a few moments after startup and drive slowly until (another word do not floor the gas pedal) reaching operating temperature.
You really will notice how much smoother the engine runs and better MPG.
If you are hearing chatter you are over pushing the engine before it is at operating temperature.
 
#5 ·
have your door or window down the next time, and everything off in the cab. upon firing it up for the 1st time(cold start) and you still don't hear the 1-2sec chatter your golden.
 
#7 ·
Thinner oil should pump faster. The the thinner cold rating of 0w vs 5w is not huge, but the tighter tolerances and reduced oil pump drag at speed help mpg and emissions. I have been outside the car when my wife starts it several times, but I was not "listening" for this issue, so maybe I missed it. I will listen in the morning and let you know.
 
#8 ·
Could it be starter noise? I have had some cars with reduction starters have a unique "gear" noise after the engine fires before the starter comes to a complete stop. A stethoscope may help pin point the noise to the timing chain/tensioner area up front under the chain cover or cam/lifter noise around the valve covers.
 
#9 ·
specifically valve train noise...others have reported hearing this as well, but the general consensus says not to get too bent out of shape about it.
 
#10 ·
It is valve train chatter, exactly like when you first start any car after an oil change.

My '15 OB does it, my wife's '14 Forester does it and the multiple OB's and Foresters I have test driven did it. It is the nature of the boxer engine with 0w oil...it just doesn't cling to the valve train after sitting for a period of time.
 
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#13 ·
I am curious as to how the valve train could be lubricated by "clinging oil" in such a way as to reduce the mentioned chatter. I could see the hydraulic chain tensioners bleeding down and causing slack, I could see the hydraulic lifters/clearance adjusters doing something similar. I am not totally familiar with how the cam timing adjustment feature is set up, but hydraulic pressure may be present there. The new synthetic oils have far superior lubricity compared to old "dino" oils. The newest highest tech engines are all using these lighter super oils. I hope the issue isn't some kind of loss or delay in oil pressure due to drained oil passages, such as a failed anti-drain back valve or poor design may cause. Every engine will suffer a little bit at startup due to low oil pressure, probably the time of most engine wear. To a lesser extent issues could be caused by differences in tolerance during warmup too. Every manufacturer recommends a warmed engine prior to aggressive driving. I don't know of any engine that doesn't sound a little different when started, but chattering, or metal on metal grinding noises will certainly worry me. My plan is to have the hood open as my wife starts the car tomorrow morning to see what I can hear. I will especially listen for valve train area noise.
 
#15 ·
I could see the hydraulic chain tensioners bleeding down and causing slack ...
Mild timing chain rattle on startup is normal and generally benign. The tensioners in the FB25 engine do include a ratcheting mechanism to limit chain slack when oil pressure is absent, but the timing chains may still be looser for a few seconds at startup than after oil pressure is restored. The perceived loudness of the startup chain rattle may vary with temperature, engine wear, and other factors.

(I paid part of my way through college wrenching on Jaguar XK engines, which were a DOHC straight 6 that employed a two-stage timing chain design. They were beautiful engines, but through the years they were fitted with at least half a dozen different timing chain tensioner variants. The SOHC flat 6 in the Porsche 911 has undergone a similar evolution of timing chain tensioner design over its life. You can learn to love the sound of timing chain rattle.)

To address the original question, some starts seem smoother than others but I have not observed startup noise I would consider unusual in my FB25 at any temperature.

When I collected my new '15 from the dealer last year the salesperson advised me, in a somewhat ominous tone, to always let the engine run a little after starting it before putting it in gear.
As soon as the engine is running smoothly, you're good to go. Eight to ten seconds should normally be enough ... which is not much longer than it takes to put on your seat belt. I've timed it, and the ECM enters closed-loop mode within 7 to 9 seconds of startup. Then drive moderately at least until the coolant temperature gauge moves off the lower peg. Nothing ominous about it.
 
#14 ·
When I collected my new '15 from the dealer last year the salesperson advised me, in a somewhat ominous tone, to always let the engine run a little after starting it before putting it in gear. He didn't explain why and to my regret I didn't ask why. Even a year later some nights I wake up in a cold sweat wondering why he said what he did. Why? WHY?!!
 
#33 ·
Same reason why I do that (tell people wait just a bit) - gives the engine a couple of seconds to get oil to where it needs to be.

What I do is tell people to reverse their procedure - normally people get in their car, put their seatbelts on, and then start the car. Instead, start the car, then take the couple of seconds to put your seatbelts on, and THEN start driving.
 
#18 ·
So I hovered over the engine when it was started this morning. A little noise from the front, but considering all the things that go from 0 to 1000 rpm instantly nothing I felt was unusual. Really no clatter or chatter in the valve train or heads. The explanation of the chain tensioners' operation and normal bringing components up to speed is more what I perceived. Also, we just turned 1300 miles and no oil loss I could detect on the stick.
 
#20 ·
Right_Mike, At least on my car there really is no "clanking" noise. I wonder if some people have loose heat shields or something else that shakes at start up. It would be interesting to find out where the noise is coming from. I had my wife start the car while I was under the hood, and the only noise I heard was from the front of the engine, around the accessory drive belt/timing chain area. Maybe others that have the clanking or chattering noise would be willing to try pinpoint the source of the noise, maybe from down lower by the sides could be heat shield or something else loose that could be remedied. Mine did not sound like oil-starved parts grindiing, valve train chattering, or tin clanking. Might be worth listening for under hood if it is bothersome.
 
#21 ·
Zim try to relax. Amin awesome as usual, thanks. This seems like a common thread/concern. So the question is, is this exclusive to Subaru and the boxer engine. Why don't we hear it more from other vehicles. I have a '14 ram hemi. It does it as well. LOUD!!!. A big v8 that's not opposed takes about 3 seconds to quiet down. Common situation. OB takes about 2 sec's and then smooth. I personally think that the aluminum hood and no engine insulation/intake cover is what allows us to hear more than others. I tongue and cheeked about putting a custom dragon style insulated engine cover to make the engine bay more attractive. It's pretty functional currently. The cover maybe the solution, making it dragon like could be a option. Like so many I have faith in the synthetic oil that most of the super high performance cars and our subaru's use. I know it's super slippery because every time I touch a bottle a $10 bill slips out of my wallet. We have a great car and drive train. Don't worry be happy.
 
#23 ·
I've never heard an engine make this noise, but I've never have a Subaru Boxer engine either, so I have nothing to go by. Mine does the same thing on cold start (over night, or a few hours). It sounds like a loose nut or bolt rolling around in the bottom of a pan for a few seconds, varying in intensity. It seems to be coming from the engine compartment. Hey, if it's "normal" and they ALL do this, it's "normal". I'd just like to know definitively, what it is. I'll be asking the dealer soon, and will keep posted.
 
#25 ·
Yesterday while at the dealer, I told the service department that when it's cold in the morning and I start up a neighborhood hill it sounds like rod & main bearings going out. But it goes away after warmed and with 13k on the ODO now it still uses no oil. He said it's common with the new engine and comes from the engine running super lean when it's cold. Not to worry.

BTW, my average mileage is nearly 29mpg and 32-34 when traveling.
 
#29 ·
Before my 15 3.6 I had a 15 2.5 and could not stand the noise- I had a knocking during low speed acceleration along with the whinny CVT and timing chain rattle during start up. My sons 14 forester was much quieter to my surprise. I'm not a fan of the current FB series engines and prefer the 10-12 EJ 2.5
 
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