Please help with this engine knock!

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tetrylone

NAXJA Forum User

Location

California

• Sep 12, 2010

• #1

I have a bit of a knock or something on a new 4.0 in an 88 XJ. Piston slap? Worse?

It goes away above about 1500rpm and isn't there when the engine is cold. Once the engine warms up it comes on slowly. Sometimes it'll go away for a while if the engine is revved and then a few minutes later it'll creep back.


Video here:
http://www.youtube.com/watch?v=HPkFOpUUdyQ&feature=player_embedded

 

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88xjlover

NAXJA Forum User

Location

Marysville, WA

• Sep 12, 2010

• #2

Hard to tell from that video but i did notice a little knock. Kinda comes and goes. You should post another one while throttling it back and forth for us. It was pretty faint on this end. Does it seem to get loud when you get at higher RPM's? Or just after you let off?

 

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tetrylone

NAXJA Forum User

Location

California

• Sep 12, 2010

• #3

88xjlover said:

Hard to tell from that video but i did notice a little knock. Kinda comes and goes. You should post another one while throttling it back and forth for us. It was pretty faint on this end. Does it seem to get loud when you get at higher RPM's? Or just after you let off?

Click to expand...

Seems to be totally quiet above 1500rpm. Even after letting up it isn't there until below 1500rpm. I will post another video tomorrow.

 

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Boostedballs

NAXJA Forum User

Location

Oregon

• Sep 12, 2010

• #4

I suspect a spun rod bearing. Check oil pan for shiny stuff.

 

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tetrylone

NAXJA Forum User

Location

California

• Sep 12, 2010

• #5

There was some glitter in the oil when I changed it. It's a newly rebuilt motor and I figured it was normal to have some glitter after the first 500 miles.

 

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tetrylone

NAXJA Forum User

Location

California

• Sep 13, 2010

• #6

Here's a couple more vids to help with troublshooting.

Here is a video of cold start:

http://www.youtube.com/watch?v=I4MhD5I52rM

You'll notice that when the vehicle is cold you really don't hear a knock.

And here is a video of the knock after taking the jeep for a ride.:

http://www.youtube.com/watch?v=6oXwyrJXTXk

I rev it a couple of times too. Please let me know what ya'll think.

 

Talyn

NAXJA Forum User

Location

Radford, Communistwealth of Virginia

• Sep 13, 2010

• #7

Sounds a bit like this: http://www.youtube.com/watch?v=153_r38bn9M ?

 

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tetrylone

NAXJA Forum User

Location

California

• Sep 13, 2010

• #8

Talyn said:

Sounds a bit like this: http://www.youtube.com/watch?v=153_r38bn9M ?

Click to expand...

Actually, it sounds exactly like that. Exact same circumstances too. WTF!?!?! Anyone know what this is?

 

Talyn

NAXJA Forum User

Location

Radford, Communistwealth of Virginia

• Sep 13, 2010

• #9

Good luck. I gave up on finding the noise. This sound has been present through two engines with entirely different components (one completely blue printed), two transmissions, two flex plates, 3 torque converters (one with each transmission plus one other). The only thing I haven't tried is that piece of aluminum between the engine and transmission.

Same circumstances. Nice and quiet when cold. When it heats up after a good drive is when it comes. I can't hear it from inside the Jeep unless I am next to something that can echo back.