Diagnosing a rod-knock

W

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Sep 11, 2005

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Mar 6, 2009

#1

• Mar 6, 2009

• #1

This topic may be a little premature, but while driving home car was knocking. I immediately parked it. I was told to wait until tomorrow and see if it stops, cheange oil also to see if it stops. It sounds kinda weird to do that. So I am here asking the great stang folks here for a little help. Car is a 94 cobra, stock. Any help/advice is greatly appreciated.

 

W

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Yay Area, California

Mar 6, 2009

#2

• Mar 6, 2009

• #2

ooops I did not notice there was a 94-95 section. I figured it was still a 5.0. If a mod wants to move it for me that would be great. (instead of making a new topic)

 

bubba-dough

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Dec 28, 2004

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Mar 6, 2009

#3

• Mar 6, 2009

• #3

How was the oil pressure?

 

95Vert383AOD

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Jun 10, 2008

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Mar 6, 2009

#4

• Mar 6, 2009

• #4

Get rid of the Fram oil filter if you have one. They are known to screw up and make low oil pressure. Could have nothing to do with your situation. But ive had about 5 Fram filters screw up on me and finally decided to use Motorcraft.

 

W

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Mar 6, 2009

#5

• Mar 6, 2009

• #5

bubba-dough said:

How was the oil pressure?

Click to expand...

the oil pressure guage in the car seemed ok. Car was not overheating either.

Ill take a look at what oil filter I have as well.

After searching it seems people are recommending a thicker oil or some lucas. I wanna try to diagnose it before I try to cover it up.

 

Dino Dino Bambino

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Jun 13, 2007

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Mar 7, 2009

#6

• Mar 7, 2009

• #6

webshot said:

This topic may be a little premature, but while driving home car was knocking. I immediately parked it. I was told to wait until tomorrow and see if it stops, cheange oil also to see if it stops. It sounds kinda weird to do that. So I am here asking the great stang folks here for a little help. Car is a 94 cobra, stock. Any help/advice is greatly appreciated.

Click to expand...

What mileage do you have on the engine?
A rod knock characteristically increases with load. If you pull the spark plug and disconnect the injector harness on that cylinder, the knock will be reduced or eliminated if it's being caused by a worn rod bearing.
Another sign is a low oil pressure at idle that increases to normal (40+psi) when you rev the engine to 2000+rpm. If the oil pressure is still low when you rev the engine up, that means your oil pump is weak as well. You can't rely on the stock dash gauge so take measurements with a mechanical oil pressure gauge.
You could try a thicker 20W-50 oil to bandaid the problem but an engine rebuild is inevitable. Fortunately you can replace the rod/main bearings with the engine still in the vehicle by removing the oil pan (not easy but possible). While you're there, you should replace the oil pump at the same time.

 

W

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Mar 7, 2009

#7

• Mar 7, 2009

• #7

what all is involved with a rebuild? Like what parts are necessary?

 

W

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Mar 7, 2009

#8

• Mar 7, 2009

• #8

turns out it most likely is not a rod knock. I am told it is a lifter or something along the lines of a bent push rod.

 

W

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Mar 8, 2009

#9

• Mar 8, 2009

• #9

I am about to take off the top part of the engine (plenum and stuff). Before I do so, just wanted to see if you guys think what was said could cause a noise that almost sounds like a rod knock. It is a above a tick, but just below some of the sound clips I have found of a rod knock. And seems to be coming from the valve cover. Almost sounds like something is hitting it.