I just uploaded a picture of my gray '91 240 sedan to the gallery for this site (not sure if it is showing up yet). I will have had it for a year in October. It's had a string of problems (some of which I got help resolving here) but is still the best car I have ever owned or driven.

The biggest problem that I am having now is a vibration at around 40-50, maybe up to 55 mph. It seems to be noticeable sometimes but not others and happens on acceleration as well as deceleration. I have had the wheels balanced twice. The second balancing seemed to help the vibration slightly, but maybe that's just my imagination. Also, it sometimes seems like it is worse when there is more weight (passengers) in the car.

Another issue is that there is a small leak at the exhaust manifold. I had a gasket replaced at a local Monro Muffler in the spring and it has started to leak from the same spot again. When I took it in to Monro again a couple days ago, the guy said there is a crack in the manifold. I couldn't see it and I really think it is just part of the gasket that is missing again. When I cup my hand around the place where it looks like part of the gasket is missing I can feel hot puffs of air with the engine running.

This brings me to probably the biggest problem I've had while owning this car - finding someone trustworthy & knowledgeable to work on it. The Volvo dealer has been hit or miss with getting to the bottom of things, but always very expensive. Most places won't or can't do work on it beyond things like brakes or tires. So if anyone can recommend a mechanic in the Upstate, New York area or in or near New York City I would appreciate it. Thanks

Dave

Would you describe the vibration as:
o Coming from the front end? -> think hub bearings, wheels/tires then suspension
o Coming from the rear? -> think wheels/tires then suspension
o Coming from the center, perhaps around the back of the driver seat? -> think drive shaft center support bearing then drive shaft U-joints
o Changes when you raise/lower tire pressure (always keep the pressure the same on both sides) to max/min? -> think tires

Read the Wheels and Tires section of the 700/900 FAQ.

Rotate the tires front to back, then side to side if needed to try to isolate a bad wheel. If the problem moves or significantly changes then it's very likely wheels, in particular an out of round tire with ply separation. If you think this is it then try swapping in the spare to help confirm/isolate this.

Check the front end. Raise the front wheels. Check for front end suspension wear by grabbing the wheels at 3:00 and 9:00 o'clock and see if there's any looseness in the vertical plane. Check for loose/worn bearings by grabbing the wheels top and bottom and see if there's any looseness in the horizontal plane. If you've got a torque wrench you can easily try re-adjusting the front wheel bearings -the Haynes and Bentley manuals have the procedure.

Because road speed and load are a key factor, I'm really smelling an out of round tire, typically from ply separation or damaged sidewalls. These wheels will dynamically balance just fine, but will deform and become out of balance such as when under load or when warm. An out of balance condition then causes speed related vibration at the harmonic sweet spots. Inspect the sidewalls for lumps (temporarily lowering the tire pressure will sometimes accentuate this). Inspect the tread grooves for cracks (temporarily raising the tire pressure will accentuate this). Ply separation can be due to a manufacturing flaw or an improper flat repair. You cannot diagnose an out of round tire by spinning it and checking for diameter variation unless you've raised and properly rested the tire overnight -even then some variation is normal.
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now

Thanks for the detailed response. The mechanic who balanced the wheels did note that the front passenger rim was bent but never mentioned it when I picked up the car. I noticed it listed on the comments section of the bill after I got home. I did have two bad tires replaced earlier this year - they had pretty severe cracks and one actually had developed a bulge on the tread which was causing the car to shake at lower speeds. It drove fine for a couple weeks then the steering became very stiff and difficult on turns. They used a crowbar on it at Monro and sprayed it with some wd40 which got rid of the stiffness, but then shortly after the vibrations began. They can be felt all through the car I would say (definitely drivers seat and front passenger seat) and the steering wheel shakes when it happens also.

One thing I should mention under the "suspension" category is disk runout. If the rotors do not run true in the lateral plane then you can have vibrations similar to a balance problem, but more like a "shimmy". It's especially noticeable on the front and will come up through the steering wheel. If your vibration problem doesn't significantly move when rotating the tires then this goes on the suspect list.

For a quick check, raise and rest the tires overnight. Then rotate the tires to check that a reference line, like a rain groove, runs absolutely true.

If not then pull the wheel and rotor. You'll need a dial micrometer with a magnetic base (cheapos are under $50). Always clamp the base to the strut/shock or other suspension part such as the axle, rather than a body part or external stand. Clean up all loose rust and dirt on the hub-to-rotor contact areas. Check the hub rounout first -mark the high/low spots. If it's slightly over spec then you can probably carry on, otherwise you've got worn bearings. Mount the rotor and check disk runout (do both inner and outer surfaces measuring about 1/2" in from edge). You can try minimizing the runout to within spec by re-orienting the rotor on different studs. Although not the Volvo approved method, you can further improve runout by shimming between the hub and the rotor using something like strips of aluminum foil. Specs on max runout (warp), max thickness variation (parallelism) and width (often found stamped inside the rotor) are sometimes difficult to find. Try Chilton's, Bentley and Haynes (in that order).

For the later 240s, the specs from my unofficial souces are something like:
o Max runout (@~1/2" in from outer edge): front and rear .004" (Chilton's has rear at .003") -caution, in/out movement from worn hubs may interfere with proper readings, push rotors in when measuring
o Min thickness: front .790" (ventilated), rear .314"
o Max thickness variation: front and rear .0008" (use high/low runout areas to determine max thickness variation problem areas)
o Max hub runout: ??? (can't find it) -caution, in/out movement from worn hubs may interfere with proper readings, push hubs in when measuring
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now

Add the steering rack and end links to the suspect list of worn items. I've had new front tires (with nice grippy sipes and deep tread) accentuate front end problems.

If a rim is badly bent then the tire will be deformed and will perform differently under various loads. If the rim is only slightly bent then a real good balancing often eliminates symptoms under normal driving conditions. Swap out the wheel for diagnosis.

If it's "shakin' all over" then it may well be at the rear end. Inspect your older tires carefully.
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now