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Knocking in 98 Outback


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22 replies to this topic

#1 808Legacy

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Posted 04 July 2013 - 09:17 PM

First, let me cut to the chase:


Recently got a great deal on a 98 Outback. Manual, 172k, yeah, yet seems solid to me, good power up hills, shifts fluidly.

yet... it was rather low on oil when I got it last week, so I added 2 quarts 10w-30 (1reg, 1 blend), and then today, 1 synth. It's not leaking anywhere, btw.

I've read other threads about similar clicks and knocks. This one isn't very loud, but my more knowledgable friend insists that it could be an issue and that I ought to change oil with Lucas and some 60 weight racing oil. I realize this could be a variety of issues and even a video isn't the same as seeing it in person. Seems to be coming from drivers side middle area. He thought previous lack of oil might have done some metal damage, like in piston or valve(s). Beyond my expertise, for sure.

The knock is so subtle, I wasn't super worried about it (the way Subarus sound), yet my friend says I need to deal with it ASAP.

Any takers?

#2 808Legacy

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Posted 04 July 2013 - 09:20 PM

Hope my video link shows up, I can't see it on my iPhone, but might just be my connection.

#3 808Legacy

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Posted 04 July 2013 - 09:35 PM



#4 808Legacy

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Posted 04 July 2013 - 09:38 PM

This was an accidental repost of the video because it didn't appear on my iPhone. 


Edited by 808Legacy, 08 July 2013 - 08:53 PM.


#5 grossgary

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Posted 04 July 2013 - 10:28 PM

video is showing up in your thread. i can't view it tonight though.

 

the lucas and racing additives are a waste of time and will not help.

 

this particular Subaru engine (not all, just this one) is prone to piston slap.  if the tapping is louder at start up and diminshes as it warms up that's classic piston slap and is benign.

 

fuel injectors can click.  mechanics stethoscope should narrow that down, place on each injector and compare.

 

the timing belt tensioners get old and can slap - creating a noise hard to distinguish from engine knock even to a mechanic because it slaps metal on metal.  generally gets worse under load...accelerating, up hill, etc.

 

any engine run low on oil will eventually eat bearings, usually rod bearings in this motor.

if it was 2 quarts low when you got it, who knows how low it's been in the past.



#6 808Legacy

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Posted 04 July 2013 - 10:51 PM

This doesn't get worse or louder under load. I'll listen closely when I drive it up hill next, but pretty sure it doesn't.

It doesn't seem to diminish as it warms up, does seem to be intermittent, or at least I didn't hear it much when my friend pulled it in just a minute ago. Restarted and it's there. But subtle.

I just listened with a piece of garden hose as a makeshift stethoscope. Def. seems to be coming from medial (to borrow another medical term) engine block, able to hear more from driver's side (but more obstructions on pass. side).

Edited by 808Legacy, 04 July 2013 - 11:27 PM.


#7 Fairtax4me

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Posted 05 July 2013 - 12:14 AM

Timing belt tensioner is on the drivers side. You can see it by removing the timing cover on the drivers side and looking in from the side with a flashlight.
The tensioner should be still, or have very little movement. If it looks like its jumping around it is damaged and needs to be replaced.

You should also check the crankshaft pulley for signs of looseness or wobbling around. The bolt in the center of the pulley can sometimes work loose and cause the crankshaft pulley to wobble around and cause a knocking type of noise.

#8 mikaleda

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Posted 05 July 2013 - 10:09 AM

What I woul like to know is why you mixed synthetic and conventional oil, I always thought that was a no go.
+1 on tensioner easy enough to check

#9 808Legacy

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Posted 05 July 2013 - 01:05 PM

Because that's what I had on hand. Same weight. Mixing reg. & synthetic is fine.

#10 john in KY

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Posted 05 July 2013 - 03:12 PM

Don't use the 60wt. My money is also on the tensioner. 



#11 efseiler

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Posted 05 July 2013 - 07:32 PM

My Dad's Subaru makes a 'knocking' sound just like that and I think he's put like 50,000 miles on it...doesn't seem to be serious. 

 

I don't think different oil will make any difference.  It's something mechanical like those guys said.

 

 

--Damien



#12 efseiler

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Posted 05 July 2013 - 07:34 PM

It does seem like kind of a loud knocking, tho.

 

 

:-/



#13 808Legacy

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Posted 06 July 2013 - 09:36 PM

Ok, went with my savant mechanic friend's suggestion and added the Lucas oil stabilizer (about 2 qts), 2 qts Lucas 70 wt racing oil, and topped it off with 15w40. No more knock!

#14 uniberp

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Posted 07 July 2013 - 10:01 AM


 

Ok, went with my savant mechanic friend's suggestion and added the Lucas oil stabilizer (about 2 qts), 2 qts Lucas 70 wt racing oil, and topped it off with 15w40. No more knock!

 

If thicker oil fixed it, it's rod knock. Matter of time. Could be a month, could be 2 years. You only risk ruining the core.



#15 Rooster2

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Posted 07 July 2013 - 11:26 AM

If thicker oil fixed it, it's rod knock. Matter of time. Could be a month, could be 2 years. You only risk ruining the core.

Agree, if thicker oil quiets the motor, then it is rod knock. Guess you could replace the rod bearings, but with 177K miles on the motor, it would be better to replace with a known good motor. My 98 OBW lives happily with a 95, 2.2 motor.



#16 auto2

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Posted 07 July 2013 - 10:35 PM

rod knock to me. piston slap is more of a double knock noise.knock-knock....knock kncok..... but real fast



#17 WoodsWagon

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Posted 08 July 2013 - 04:29 AM

2qts of lucas is way to much. 1/2 quart at the most, rest regular oil. You're going to destroy the engine because it will not move enough oil through the bearings at cold start. It's like pumping molasses.

 

It sounds like either piston slap or rod knock. Hard to tell with out revving it up and snapping the throttle shut and listening for the back-rattle of a dying rod bearing.

 

With piston slap you can run normal oil and ignore it and it will run fine for the next 1OOk miles. My mom's 98 came with horrendous piston slap, and ran fine, got good mpg, and was problem free for the next 5 years. It sounded like a diesel in winter, and the piston slap didn't quiet down much when warmed up. Embarrassing, but it ran fine so whatever.



#18 johnceggleston

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Posted 08 July 2013 - 06:09 AM

info below is from 

Engine Diagnosis 101

not all of that link is noise related, but still a pretty good link.

 

 

 

When your engine is cold, the aluminum piston is small in comparison to it's
surrounding iron cylinder. Why? Because with heat, aluminum expands
roughly 5 times as much as iron. Therefore the rather hollow piston slapping noise
will be loudest first thing in the morning. After the engine warms up,
the aluminum piston expands more than it's iron cylinder, reducing the excessive clearance
between the piston and cylinder wall.


So, the test is this:


First thing in the morning, start the engine up and run it for 15 seconds
while you listen carefully and memorize the sound and it's intensity.
Shut it down quickly, pull the spark plugs and put two squirts of motor
oil into each cylinder. Reinstall the plugs, fire the engine up again
and listen.


If you have piston slap the noise will have been greatly reduced or even
eliminated…..for 15 or 20 seconds that is, and then your nightmare
noise will come back like a Marine Corps marching band coming toward you
in the parade.

 

Rod knocks are loudest at higher speeds (over 2500 RPM) Feathering the gas
pedal may result in a distinctive back rattle between 2500 and 3500
RPMs.
Bad rod knocks may double
knock if enough rod bearing material has been worn away allowing the
piston to whack the cylinder head in addition to the big end of the
connecting rod banging on the crankshaft rod journal. It will sound like
a hard metallic knock (rod) with an alternating and somewhat muffled
aluminum (piston) klock sound.
Wrist pin knock in modern engines is very rare today but is a favorite for the
misdiagnosticians.


Determining which cylinder contains the noisy parts may be aided by shorting out
the plug wires one by one with a common low voltage test light.


Now you won't get the bulb to light up but it is a convenient way to short
the cylinders without getting zapped or damaging the ignition coil.
Attach
the alligator clip to a convenient ground, away from fuel system
components, and pierce the wire boots at the coil pack  or distributor
end of the wire.

(Some guys will use straight pins stuck in the ankle of the wire boots in the
distributor. You know. The guys with tattoos and key rings stuck in their
eyebrows. Then they touch a grounded jumper wire to each one.
)


If the noise is changed when the plug wire is shorted to ground, you can figure
that the problem is in the reciprocating bottom end parts. (piston,
wrist pin, connecting rod or connecting rod bearing)

The reason the sound changes is that when you short the cylinder
plug wire you are stopping the combustion chamber explosions that are
slamming the piston downward making the inside of the big end of the
connecting rod bang against it's connecting rod journal. Or in the case
of piston slap, no explosion changes how the piston is shoved hard
sideways against the cylinder wall.


If you get a change in the sound when you short a cylinder out it may
become moot as to what the problem is because the oil pan and cylinder
head must be removed to correct the problem. [Generally speaking, an
engine with damage to reciprocating parts (pistons, rings, connecting
rods, wrist pins or rod bearings) and more than 70 thousand miles is not
cost effective or risk free enough to attempt to repair. Replacing a
crankshaft, for example while the rest of the engine has 70k perfectly
maintained miles on it is risky enough but whatever killed the crank has
scored the rings and packed the lifters with debris and smoked the
piston pin bosses etc.

If the sound doesn't change, look at parts other than the reciprocating
ones. In many cases of rod-knock or piston slap, more than one is
banging so even if you eliminate the noise from one rod the other one
will still be a-banging away with a different, more singular tone.

Valve train noises generally are loudest up to 1500 rpms. Lifters are
also misdiagnosed commonly as the source of many noises when in reality
they are quite trouble free,
sorta. Dirt contamination on a sludged engine is the number one cause of
true lifter noises, low oil pressure is number two, . Whatever you do,
don't put engine flush in a sludged engine! We call it "Instant rod
knock" because of the way it overloads the oil filter to the point of
opening the filter bypass valve, flooding and destroying the engine
bearings with mud. The only safe way to clean a sludged engine is to
accelerate the oil changes and let the detergent in the oil do the
cleaning at a controlled rate. Like every 500 miles

 

By the way, if you have low oil pressure, don't bother putzing around with the valve
train because the damage you find will be the result of low oil pressure
and will return after you spend a bunch of money on valve train parts.
Over nineteen engines out of twenty that we tear down with low oil pressure
do NOT have bad oil pumps but have worn out bearings and journals so
quit with the wishful thinking about just putting a pump in it.
Think about it, usually,  an oil pump is two dumb ol' iron gears spinning
around immersed completely in oil. EVERYTHING else in the engine has a
tougher time of it than the oil pump.


 


Edited by johnceggleston, 08 July 2013 - 06:16 AM.


#19 efseiler

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Posted 08 July 2013 - 01:29 PM

Yeah that's a lot of Lucas...I usually only put a few ounces in my 2.2L engine.



#20 808Legacy

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Posted 08 July 2013 - 08:43 PM

2qts of lucas is way to much. 1/2 quart at the most, rest regular oil. You're going to destroy the engine because it will not move enough oil through the bearings at cold start. It's like pumping molasses.

 

It sounds like either piston slap or rod knock. Hard to tell with out revving it up and snapping the throttle shut and listening for the back-rattle of a dying rod bearing.

 

With piston slap you can run normal oil and ignore it and it will run fine for the next 1OOk miles. My mom's 98 came with horrendous piston slap, and ran fine, got good mpg, and was problem free for the next 5 years. It sounded like a diesel in winter, and the piston slap didn't quiet down much when warmed up. Embarrassing, but it ran fine so whatever.

So, I am in Hawaii, temp. never gets lower than 70-75 deg., so there is no "cold" cold start (unless I spent the night on Haleakala (10,000ft) or lived way upcountry above 5000ft. Thick oil turns lighter fast out here.  

I am very apprecitative of everyone's input here; I am going to try the cylinder experiment in the morning.

 

Seems like the knock is now much lower in volume and very intermittent, btw.  I'll post another video soon.   



#21 808Legacy

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Posted 09 July 2013 - 12:17 AM



#22 heartless

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Posted 09 July 2013 - 06:39 AM

2qts of lucas is way to much. 1/2 quart at the most, rest regular oil. You're going to destroy the engine because it will not move enough oil through the bearings at cold start. It's like pumping molasses.

 

This x 2!

 

initial (cold) startup is the most important time for oil distribution - thick oil does not distribute well right away, especially thru small oil passages - which these engines have.

 

"Cold" startup has little to do with ambient temperature - more to do with the fact that the car has been sitting, and oil has drained away from areas higher up in the engine. Getting oil to those areas quickly is critical on initial start.

 

You may "think" you have solved the mystery knock, but in reality, you are probably causing more damage.



#23 ivans imports

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Posted 09 July 2013 - 10:09 AM

Piston slap is running to smooth for bad rod take out #4 #2 pistons knurll them and put them back in sound will be gone. But realy start with pulling the oil fillter and dumping it out into a pan tant you can see if any meatal or berring materail in the oil. Have heard worse piston slap than that always #2/4 that slap have you treid pulling the wire of on that cly and see if noise stops when not firing ?also a oil preshure check helps min 10 psi hot at idle. And oil light should go out in under 1 second cold start






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