Front end noise question

First, I know this is a long post sorry. Thank you for taking the time
to read it and give advice.


"95 Saturn SL-2- 80K miles

I have an odd issue. I've been a shade tree mechanic for 20 or more
years. Never seen this one and it's really putting a teaser on my brain
trying to find it. I have a rapid knocking noise in the passenger side
front end that is only present when the vehicle is cold. The sound is
very close to a badly loose cv joint with a lot of movement. It is
speed dependant and pressure (engine must be pushing) dependant. The
knocking can be felt through the floor. Take the car out of gear the
sound goes away. In gear the sound returns. Pressure on that side of
the suspension makes the sound worse.

The sound goes away all together after a few miles of driving (because
the car is warmed up?).

I've done a bunch of testing.
-There are no error codes in the computer.
-Tire has been removed and joints checked by manual turning of axle
against parked transmission. No looseness or extra sounds noted.
-Visual inspection of shock showed nothing extraordinary. Manual
pushing/pulling against shock showed nothing. Striking shock with
sledge hammer showed no unusal sound.
-Rod arm is tight. Dust boot is completely torn, but no wear is evident
to account for any noise there.
-Stethoscoped belt driven under hood components. Idler pulled is going
bad (noisy bearing) but has no play in it. all else is normal.
-Full on tight turn testing done in both directions without any noise.



Some theories:
-CV Joints? the most obvious, but no classic symptoms (popping in tight
turns, clicks in joints under manual test)

-Loose suspension piece? (thorough inspection none found)

-Idler Pulley?- (probably not as sound disappears with transmission
disengaged and pulleys should not be able to know when pressure is on
engine)

-Motor Mount? - (Sound is speed dependant so probably not)

-Misfire into exhaust? (Should show up on O2 sensor yielding a code in
computer)

I'm lost on this one. Anybody have any ideas or thoughts on what I've
missed here. Or maybe I've dismissed an idea I should not have?

-Mark

 

Support bearing on the passenger side axle shaft?

Ken

 

or transmission mount on drivers side

 

Definitely appreciate the input. Trans. mounts I can inspect fairly
easily.

Do you have any thoughts on how to inspect the support bearing?

-Mark

 

wouldn't a support bearing be audible with the car rolling and out of
gear? What I have is not.

 

Visual inspection of seals. Rotate the shaft back and forth watching and
listening for anything abnormal.

Ken

 

What you say makes sense, but stranger things have happened. This is not
something that has been mentioned here very much, but I'm just brainstorming
from the information that you provided in your OP.

Maybe Lane will weigh in on this?

Ken

 

I'd replace the idler pulley if you believe it is marginal, and then re-do
your tests.

I recently had a roaring noise from the front end that would only be present
when driving straight ahead. I ended up putting the car on jackstands,
putting it in gear, letting it idle, and listening. I repeated this after
removing the wheels, then the brake calipers, then an axle (you need a plug
to keep the fluid from running out of the trans to do this though, and I'm
not sure it's the healthiest thing to do...). By pulling parts out of the
equation, it made it very easy to determine what it was. Ended up being a
wheel bearing. Didn't take all that much effort to remedy and saved a lot
of $$ by doing it myself. BUT, I was also very ready to take it to my local
Saturn to have them do a diagnosis if I wasn't able to determine what was at
fault myself. Paying their fee is almost always cheaper than guessing and
replacing any parts that don't need it.

Good luck!

Lane [ lane (at) evilplastic.com ]

 

Thanks so much p_vouers, Ken, and Lane. I'll be doing some exploring
this weekend again with these items in mind. I'll [post some info on
Monday.