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Need help diagnosing "throbbing" in front left of 9000 Posted by dbreid [Email] ![]() ![]() |
All,
Firstly, this is my first post, and I signed up for a membership just to ask this question as it has me stumped. I will write a lot in an attempt to give the full rundown on the problem.
I bought a 1993 Saab 9000 Aero about two weeks ago. I bought it from the second owner and it is in overall excellent condition. No cracks in the leather, TCS works perfectly, all the usual stuff has been done with receipts (Clutch Slave, Heater core, etc). The car runs great. Everything from seat heaters to A/C work flawlessly. And it is a real joy to drive.
However, when I bought it, it had a "throbbing" in the front left (drivers side) of the car. Let me describe the sound. It is speed related, and has nothing to do with the engine (coasting sounds the same). It is clearly on the left hand side of the vehicle, and gets louder on right hand turns (like sweeping off ramps, etc). It is not a "clicking" or a "grinding" or a "scraping" noise at all. It speeds up when you speed up and slows down when you slow. There is no feedback or throb in the brake pedal when braking in either forward or reverse, and the brake pedal has good feel.
Now, on to my diagnosis and what I have done.
My first thought was that the tire had a flat spot, or had separated, or that a rim was bent or something. SO I took it in immediately to have them check it out (I took it to a tire place I have used for year - I have 7 cars currently) and they said that though the tires hadn't separated, there was some irregular wear. I bought 4 new tires and had them mount and balance them. I drove it home, and that was NOT the issue. The sound was still there.
Sigh...
So I thought more about it, jacked up the car and looked, and though the Wheel bearing felt tight, I decided to put in a new wheel bearing. I ordered a new one, and put that in as well (myself). I torqued the axle nut back to 210 pound Feet, used red locktite on the wheel bearing bolts, and checked the rotors for wear and drag. Everything looked good.
So I bolted it all together again, and drove it.... NO CHANGE at all. Sound is still there.
Now I am wondering what else it could possibly be. I generally don't like just throwing parts at a problem, and labor is free, because I do it all myself and have all the proper tools, but I am flummoxed.
I thought about warped rotors, but I should be able to feel that in the pedal...
I thought about bad CV joints or axles, but I would be able to hear clicking when turning, or the sound would have to do with getting on and off the throttle. Plus, the boots aren't cracked.
There in't much else that rotates in the front of the car, so I am at a bit of a loss. I can't imagine how ball joints or anything would make a throbbing noise... I suppose possibly it could be that somehow the axle shaft itself (between the CV's) is somehow bent? That would be bizarre, but stranger things have happened....
Thanks in advance for any ideas.
This is my first Saab, and I am enjoying the heck out of it. But I want to track this little issue down, because it is now bothering me. :)
-Dan
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