We have a 2001 Volvo S40 that has 120,000 miles and is in very good condition. We maintain it faithfully, observing the major milestone service recommendations, oil changes, etc.
About a year ago, the car suddenly developed a few noises, which may be related.
1) The first noise is in the front-end, and sounds like a lower-pitched version of a couple of billiard balls hitting each other. That is, the noise is of short duration and well-defined in time. It's not
really a "rattle", which suggests a series of sounds, dying out over time. It's not so much a "thwack", like billiard balls, but
a "thwock". The first appearance of the noise was in the right-front of the car, and was diagnosed by one mechanic as a broken motor mount. The mechanic performed that work, and we went on our way.
A few months later the noise returned, still somewhere in the front-end of the car, although my wife maintains that occasionally
the noise seems to come from *behind* the passenger compartment. I've never thought this, but so be it.
2) Around this same time, we noticed that the right-front strut or spring, presumably, was in need of service. Everytime we would
creep over a speed bump in the neighborhood, the right-front suspension would "groan" as we rolled down the far side of the speed bump. But... the groan only occurs when the car is cold. When we car is warm or hot, no groan. This groan is quite consistent and reproducible.
So we took the car to a different mechanic, and he claimed the sound was related to a right-front strut needing repair. Something about the bushing. This bushing repair seemed to help, but within a few weeks, the speedbump groan was back. Maybe it never left, as I was perhaps hearing what I wanted to hear, or not hear.
And so is a new "thwock". But now the thwock seems to be originating in the *left* side of the front-end, not the right. But the groan remains squarely on the right side.
The thwock has always, to my mind, been audible when travelling over washboard-bumps while turning the wheel one way or the other,
and seems (maybe) to be correlated with which way we turn.
The car otherwise handles fine, and no indication of steering wheel or front-end vibration or wobble is observed at any speed, slow or fast.
3) In the morning, the car seems to run a bit rougher than it should. Not only can you feel this roughness as you sit in the car, you can also hear it when the car is started in the garage, where the sound
is confined for the hearing. The new mechanic claims that the
roughness is not a lack of "tuning" in the engine, but is vibration-related. Interesting. Vibration and thwock themes again.
This roughness seems to diminish when the car warms up. Just like the groan goes away when the car warms up. Hmm.
So the car has three sounds that may or may not be related: thwocks that were attributed to motor vibration to a broken motor mount, groans coming from the right-front strut, and cold start roughness
that eventually goes away when the car warms up.
We have, over the last few years, hit a pothole here and there. Maybe this has caused something to break that is, as it turns out, is hard to diagnose? Really dunno.
Anybody have any idea on what may be going on here, and whether these sounds are related or not?