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  • SN95 4.6L Mustang Tech

engine started knocking! but then stopped

  • Thread starter Thread starter ceracer33
  • Start date Start date Apr 17, 2008
C

ceracer33

New Member
Aug 30, 2005
118
1
0
Apr 17, 2008
#1
  • Apr 17, 2008
  • #1
let me start by saying that i do not daily drive my stang. she has been sitting since sunday. i went out tonight to go the gas station and fill her up. i checked the oil and was half a quart low, kinda odd but i just topped it off and thought nothing of it really. got in the car and started it up and the engine was knocking pretty loudly. it sounded JUST like a rod bearing had spun. i shut it down after a few seconds, and just cant for the life of me believe that it was a rod bearing. the last time i drove her everything was fine. so i fire her back up and she sounded perfect. no knock at all. drove down to the store and filled up, romped on her a little on the way home, and she ran great with no signs of a knock. i even left her running while i pumped gas so i could pop the hood and listen closely. nothing. so my guess is that maybe i have a lifter thats worn and starting to bleed down on me while she's sitting. thats the only thing that makes sense to me. it must have pumped back up right as i shut it off the first time, so when i fired it up again it was pumped up and didnt knock. only problem im having with this theory is that i did not sound like a normal lifter tap from the top end. it definately sounded just like a rod knocking. anyone ever heard of a rod bearing knocking and then stopping? if i did indeed throw a rod bearing guess i'll be doing that 5.4l swap sooner than i thought.
 

BurningRubber

10 Year Member
Dec 6, 2004
1,865
24
58
Apr 17, 2008
#2
  • Apr 17, 2008
  • #2
Some of the accessories can knock if they are going south, mainly the idler pullies.

If you have a rod knock, you have a rod knock. It should be constant.
 
C

ceracer33

New Member
Aug 30, 2005
118
1
0
Apr 18, 2008
#3
  • Apr 18, 2008
  • #3
right see thats what i was thinking about it being a rod knock, it should still be doing it if thats what it was. it damn sure sounded just like a rod bearing though. i have pretty mucn convienced myself that it must have been a lifter that bled down while it was sitting for a week. i drove it to work this morning and everything is fine. im not getting a knock at all so i think thats what it was. it just sounded too solid to be a lifter, but thats what it had to be.
 

bhuff30

Founding Member
Dec 11, 2001
6,037
35
129
Olathe KS
Apr 18, 2008
#4
  • Apr 18, 2008
  • #4
A rod knock will definately be worse when the engine is hot. Cold viscous oil takes up the extra clearance so you may not even be able to hear a rod knock when the engine is cold. Sounds very likely that it could be a lifter. You may never hear it again, or it may become a regular occurance.
 

georgio440

Member
Nov 22, 2007
195
0
17
Walnut Creek, CA
Apr 18, 2008
#5
  • Apr 18, 2008
  • #5
Sounds like the issue I had...








I'm picking the car up today with a new motor in it.
 

bhuff30

Founding Member
Dec 11, 2001
6,037
35
129
Olathe KS
Apr 18, 2008
#6
  • Apr 18, 2008
  • #6
That is an absolutely worthless reply. What was the car doing? What was the problem? Why did the engine need replaced?

georgio440 said:
Sounds like the issue I had... I'm picking the car up today with a new motor in it.
Click to expand...
 

georgio440

Member
Nov 22, 2007
195
0
17
Walnut Creek, CA
Apr 18, 2008
#7
  • Apr 18, 2008
  • #7
No need to get your panties in a wad. I had a spun rod bearing.
 

bhuff30

Founding Member
Dec 11, 2001
6,037
35
129
Olathe KS
Apr 18, 2008
#8
  • Apr 18, 2008
  • #8
I've spun rod bearings before. They don't knock when cold until it gets really bad. You'll definately notice at knock at 2000 rpm when hot LONG before that.

And I didn't have to replace the engine for a spun rod bearing.

georgio440 said:
I had a spun rod bearing.
Click to expand...
 
R

rugster

New Member
Aug 31, 2004
156
0
0
Apr 18, 2008
#9
  • Apr 18, 2008
  • #9
Replaced my bearings today with Clevites
 
F

FullRace

New Member
Dec 10, 2006
41
0
0
Apr 19, 2008
#10
  • Apr 19, 2008
  • #10
If you start it up and it has been sitting the oil probly didnt make it to the topend and the valvetrain was clanking? Should go away in a few seconds if it does it, which sounds like what happened to you..
 

screamin gt

5 Year Member
Apr 9, 2007
393
6
28
central CT
Apr 19, 2008
#11
  • Apr 19, 2008
  • #11
bhuff30 said:
I've spun rod bearings before. They don't knock when cold until it gets really bad. You'll definately notice at knock at 2000 rpm when hot LONG before that.

And I didn't have to replace the engine for a spun rod bearing.
Click to expand...

I didn't have to replaced my motor for 2 spun rod bearings. and if I knew thats what it was when I tore it apart I'd have done even less work than I did to it.


FullRace said:
If you start it up and it has been sitting the oil probly didnt make it to the topend and the valvetrain was clanking? Should go away in a few seconds if it does it, which sounds like what happened to you..
Click to expand...


 
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