Please help me identify this strange knock, 94 GS-R

Top-Ace

New Member
se help me identify the source of this knocking sound. It is not audible when the engine is cold and gets worse as it warms up. At higher revs greater than 1200rpm it is not audible. It doesn't sound like the videos of rod knock, piston slap, or spun bearings that I have heard.

It occurs at either clutch position. It is really audible if I stick a screw driver on the exhaust manifold. It as 237,000 miles and has done it for at least 50,000 miles with no change.

The head has new Lost Motion Assemblies, valves have been adjusted, new TD-68U distributor, wires, NGK plugs, and a new timing belt all with no change.

It runs great, lots of power, idles great.

http://www.youtube.com/watch?v=9eci6EHfwQ8&feature=youtu.be
 
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Integraguy04

CORNER CARVER
So I listened to it - the thing I noticed the most is that the sound does not change when you rev the motor it stays the same tone/frequency. With that being said I would think it would be something not related to the motor and doesn't vary when the load/rpm on the motor changes..not really sure what it is though


Sent from my iPhone 4S
 

Ganyon

Active Member
Have you jacked it up to see if something is loose under the car. It kinda sounds like something loose.
 

Top-Ace

New Member
Ya I have looked all over the place and can't see anything. I'm sure it is coming from the engine, I think lol. One thing I have noticed listening to some videos of other idling GS-R's, is that many make the same noise, just not near as loud.

If you listen around the 43 second mark and 103 second mark it does speed up when I revved the motor, but it quickly stops. You can hear it but you need to pay close attention
 


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Muckman

Not a M0derator
Lets rule out a few things. Drain the oil and look for metal flakes in oil which would be evidence of bearing damage. This is easier if you have a magnetic drain plug.

Did you recently install a new clutch? Pull the starter and inspect the pressure plate bolts. Make sure they are torqued to spec.

Check the valve lash [AGAIN].
It could be a bent [exhaust?] valve. With the VC off slowly turn the motor over and watch al the valves go up and down. See if any valves stick.
 

dc4_illinois

Local Troll
This happened to both of our cars, the sound drove me nuts.

These are just "could be" situations for ya:

On the Grand Marquis, it was a loose exhaust heat shield, shielding the driver's side exhaust tubing. Got under there, pulled the bolts and threadlocked em back in.

On mine, the bracket that holds the exhaust to the rear of the engine was loose and vibrating. I did the same thing with the bolts and the sound is gone!

In the beginning, it sounded like engine/trans troubles... But i had no power loss, I could stomp the gas anytime and either car would put a smile on my face. It really helps to pull your vehicle up onto some ramps, or jack it up and cinder block it.
 
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Top-Ace

New Member
Well I give up. I snugged down all of the exhaust brackets. I pressed everywhere with a screwdriver. I took my nice stethoscope and went under the engine and around everything. I can't find where it is coming from. It doesn't sound lower end, there isnt hardly any noise coming from the oil pan.

The sound is most pronounced on the exhaust manifold. About three months ago I replaced the exhaust manifold gasket because it was leaking on the passanger side. The three studs furthest on the left just sort of twisted appart and I assumed the manifold warped and stretched them. I had the manifold resurfaced at the local NAPA machine shop. Maybe there is some sort of small crack in it that could cause this noise??? The noise was exactly the same long before and after this repair.

It sounds more like the head, but does not get louder if I remove the oil cap lol. The only thing I can think of is maybe a rocker has some play side to side, or some sort of minor scuff or something in the cylinder.
 


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Jeffbel

New Member
Mine made the same sound when the o2 sensor wasn't torqued. Simple but could be the problem.
 

Top-Ace

New Member
Pulled the valve cover off and re-torqued all the bolts with my torque wrench and still no change. I did not feel any exaust puffs coming from the intake manifold either :x . I re-did the exhaust bracket behind the Y pipe and re-torqued the O2 sensor.

I EVEN put in half a bottle of lucas oil stabilizer just for fun. Didnt even change it.

Could this just be a characeristic of the engine? I can kinda hear the same noise in some other GS-R's but just not near as loud.
 

Top-Ace

New Member
It is not coming from the transmission, that I do know. It seems to be the head but you can hear it down low on the block too. The loudest spot is if I put my stethiscope on the exhaust manifold, which could mean anything really lol.
 

Top-Ace

New Member
Well, if anyone stumbles across this thread and wants to know, too bad I sold the car lol.
 
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