What could make an engine audibly knock??

Heads, valves, pistons, rods, crankshaft, etc...

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NuclearBacon
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What could make an engine audibly knock??

Post by NuclearBacon »

Spent my time searching, and didnt come up with a definitive list of what exactly would cause an engine to knock. Minor things? Major things?

Specific examples?? :) Lay it on me!

edit.. i mean, in our 2.2 Turbo engines. :) I did a search on google and read up on it, now im more curious about specific examples :) thanks again!
-Luigi-
....Yes like nintendo
1987 GL10 Sedan 3.700 LSD
1988 XT6 FT4WD 3.900 Diff Lock
1992 EJ22T Touring Wagon 5MT Swap 4.111
Legacy777
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Post by Legacy777 »

Knock like rod knock, knock due to detonation?

At idle or while driving under load?
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
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If you need to get a hold of me please email me rather then pm
log1call
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Post by log1call »

You need to take more careful notice of the symptoms.

Start the motor from cold and listen under the bonnet. See if the noise is loud or quiet. Give the motor a tiny rev, perhaps to about 1500 revs and then let the throttle off again. Did it make the noise when you had the revs up? Did it make a noise for a second just as the throttle went off and the revs were about to slow down again. Get in the car and put it in gear with the brakes on, let the clutch up till the motor nearly stalls at idle, does it get noisy? Keep the brakes on and give it a little throttle with your toe then try nearly stalling it, does that make it noisy?

Now go for a drive and warm the motor up. Repeat all those tests again.. idling, reving in neutral, light load, heavy load.

Take notes and compare the noises, rate then from one to ten perhaps. So there might be a small noise at idle cold, it gets louder warm and a lot louder when under a load either cold or warm but worse warm than cold. Perhpas the cold load noise will be louder than the warm idling noise.... take careful not of all the sounds and conditions. Be systematic in your test.

Come back and report and someone will be able to help diagnose it or recommend what to test next.
NuclearBacon
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Post by NuclearBacon »

I don't have the car yet... and haven't listened to it. Ive seen it sit, and was told it has a knock .

that's where i am, when i get more info, I'll let you know!

Thank you for the info so far!!!! :) I'll keep you posed. car is showing up around Friday.

from what i know, it has a knock at idle, and the owner drove it to go through all the gears. you now know all that i know.

and log1call, thanks for the map. that's close to what i was thinking about doing when i received the car. I'll let you know!

also... the car is about 4 miles away from my house. it didnt overheat (i was told) do you think with proper lubricants, i'd do any damage driving it easy the 4 miles to my house in the middle of the night with barely any lights? I dont want to blow it up... but i figured i could save $50 on a tow. i already have a rig set up to tow (if you're shaking your head as you read going "DONT DRIVE IT!!!") just curious if it would..make it ?? thanks!
Last edited by NuclearBacon on Tue Nov 10, 2009 3:51 am, edited 1 time in total.
-Luigi-
....Yes like nintendo
1987 GL10 Sedan 3.700 LSD
1988 XT6 FT4WD 3.900 Diff Lock
1992 EJ22T Touring Wagon 5MT Swap 4.111
Mattheww044
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Post by Mattheww044 »

He likes the :) face :D
1991 Subaru Legacy SS 5MT: Revtronix Stage 2 Set-up with a few other "tasteful" mods :D
ericem
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Post by ericem »

If it is very slight knock then sure why not might be a couple seized HLA's!! They can be pretty loud!
1993 Subaru Legacy L AWD Wagon R.I.P
1994 Subaru Legacy SS R.I.P :(
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asc_up
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Post by asc_up »

If it's a bottom-end knock, it probably won't get you too far, so have that tow truck on call. A bottom-end knock will sound very deep, much like a hammer hitting a solid piece of metal (which is essential what it is/is happening).
-Aaron

2000 Audi S4 - 2.7L Twin-turbo, 6 Speed

[quote="evolutionmovement"]It was me. And those are my balls. Happy Sunday![/quote]
NuclearBacon
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Post by NuclearBacon »

If its the LOUD knock, im not going to drive it anywhere... unless the damage is already done... and i can save $50 or so.... hopefully thursday i'll hear it run.. if not then, this weekend for sure.
-Luigi-
....Yes like nintendo
1987 GL10 Sedan 3.700 LSD
1988 XT6 FT4WD 3.900 Diff Lock
1992 EJ22T Touring Wagon 5MT Swap 4.111
NuclearBacon
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Post by NuclearBacon »

I went out and took a BUNCH of photos of the cars interior and exterior. as well as some engine shots... Enjoy ... theres 70 ;)

Photobucket Album
-Luigi-
....Yes like nintendo
1987 GL10 Sedan 3.700 LSD
1988 XT6 FT4WD 3.900 Diff Lock
1992 EJ22T Touring Wagon 5MT Swap 4.111
Kelly
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Post by Kelly »

Go get yourself one of these. http://www.harborfreight.com/cpi/ctaf/d ... mber=41966

Run it and probe around to find out which part of the motor its coming from.

Ive seen munched up trans input shafts sound like motor knock too, so usually the first thing I do is engage the clutch to see if the knock goes away.

Pistons in these motors can get noisy, especially if the bores have been honed out making it a bit sloppy in there. The piston skirts will wear down on the bottom and go oval. Kinda unlikely though unless you know the blocks been split before.

If it is a rod on its way out, there should be some shavings in the oil too. Remove the oil filter and cut it apart. If you find little gold and silver shavings in there I'd probablly start looking for a crank.

Good luck!
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