I Hear Yah Knockin'

[MrWizard]

For months I've been chasing this knocking noise in my 1994 Explorer.

When I turn right, I hear a distinct knock somewhere around the left front wheel area. A single thunk, like you took a heavy
metal bar and whacked it against another metal piece.
Never happens when you turn left; only when you turn right.
And once in a great while, you hear the thunk after you start off from a dead stop. But you don't hear it when going over bumps, etc.

For various reasons, I've replaced the Radius Arm Bushings, the tie-rod ends, front brake pads, anti-rattle clips, flex brake lines.
Also replace the wheel bearings, and checked that they are not loose. Pushed/Pulled the top and bottom edge of the tires, when lifted.
No movement. Pushed/Pulled left and right edges of tires. No movement. Seems like the bearings are okay.
For a while I thought it might have something to do with the brakes, since when I replaced the anti-rattle clips it seemed like
the noise was less. But now it's back.

btw, it's a 4x2, so none of the usual other 4x4 sources would be the cause.

Anyway, at a total loss on how to get rid of this damn noise.
The last time I ignored a strange noise, I ended up stranded by the side of the road with a fried transmission in my Mustang.
So, turning up the radio, and ignoring it - probably not a good idea.

Any ideas?

 

[Paraphoe]

Sway bar?

 

[MrWizard]

Darn. I forgot to mention, I also replaced the front and rear sway bar bushings with Energy Suspension poly ones.
Didn't get rid of the knock, but the whole truck feels more like it did when new.

Also replaced the front shocks, and the rear leaf spring bushings.

 

[Paraphoe]

Dangit. Thought I had it.

 

[corkey]

body mounts ?
motor mounts?

 

[MrWizard]

Never even occurred to me to check the motor mounts! That might explain the clunk in one turning direction only.

I looked at them tonight. Visually they look okay. Not old or rotten looking.
(Unlike the leaf spring bushings which looked like old tree bark.)

But figured there is so much torque on the mounts that even if they visually look okay, they may still be loose or rotten
under the covers, which might be enough to knock the engine mount point against the frame.

I rigged up a video camera and recorded the engine movement around the driver side mount, with the truck in gear and
rev'ing the engine a bit. For some reason the wife didn't want to get underneath the truck with it in gear and me at the wheel....
I have no idea how much movement is too much, but the engine moved maybe a 1/2 inch - 1 inch at the mount point. But no clunk.

Can I presume they are still good? Looks like it would be a bear to jack up the engine enough to get the old mounts out,
so shot-gunning it may be a pain.

 

[kelvin37]

i have a 91 but it is 4x4. i have the same clunk on the front left. i did the same thing you did with the camera but i put it just above the front left tie rod and all. what i saw is my upper bolt for camber adjustment and alignment moving when the clunk happened. and i talked to a ford tech and he said that the excentrics for alignment was bad. i have not fixed it yet just cause i am to lazy when its a 115 out here. good luck