My shop says I need new rotors on my 90 740 turbo wagon (ABS)

So I ordered some new rotors. Pads were replaced not too long ago, wasn't going to bother replacing them, but now I'm worried that I should. Any thoughts on this?

I've been advised to use caution working with the ABS systems, do these warnings apply for simple rotor replacements? Do they apply if I end up replacing the pads?

If the brakes are working (you just repalced the pads) what's with the rotors/
Does the shop say they're warped?
Are you getting pedal pulsations?

Generally, there is no such thing as warped rotors...it's often just uneven pad material displaced onto the rotors.

Take the car out on a deserted road or where there are no cars around and do about 10 69-20 mph braking cycles using moderate to strong, not emergency, braking...don't stop the car. Let the brakes cool a minute or so between cycles while you bring the car back up to 60. You should smell some brake smell as the brakes get some heat into them. Watch for brake fade..if you get it you have other problems, probably old brake fluid or bad pads (other than volvo OEM there's a wide range from excellent (Hawk) to poor.

Shop says to replace the rotors because they measured them and they are inconsistent thickness by the calipers. I can turn them myself and feel where they are alternatively tight and loose. The rotors were resurfaced by previous owner (who drove the car hard) about a year ago, and then he recently had new pads put in.

When you brake at higher speeds there is a vibration from up front, not so bad at lower speeds.

If I jack up one wheel and try to turn the tire there is some play - I believe in steering linkage, maybe half a mm at the tire. My local alignment shop said it was so bad they couldn't align the car, but my local Volvo shop said they were just wrong, and rotors was what the problem was, tie rods were in spec.

The usual caution with ABS is to open the bleeder screws before pushing the pistons in, to avoid pushing old brake fluid up into the ABS modulator. Some advocate pinching off the flex hoses while doing this, I personally don't like the idea because the inner liner of a flex hose is actually fairly rigid. Also be careful not to damage the ABS sensor at the hub, and while you're there it doesn't hurt to clean the notched wheel that runs by the sensor - just brush out any gunk that's accumulating there to prevent future problems. As far as reusing your old pads, I suppose you could, but bear in mind your first few stops may be harrowing experiences until the pads are seated to the new rotors. The old rotors will have worn matching grooves in the pads so until those grooves wear down, a minimal amount of pad touches the new, flat rotor. In my starving student days I resurfaced the old pads on a belt sander, just enough to make them flat. A good particle mask is essential, and probably still not good enough for the risk involved though.
-Chris

Thanks, used your tips and did the job last night, everything seems to be working great although I haven't tried to test the ABS system at this point.

I bought a new set of pads, and they are stopping nice and smooth.

No more chatter, so my shop seems to have been correct that my pads were warped or uneven. In fact you could see the inconsistency just looking at them, not sure how they got that way!

Thanks for the advice, came in really handy.