I recently purchased a 1992 Volvo 240 wagon for my son. It is in remarkable shape for its 229,000 miles. I only had to correct minor problems in the cooling system and electrical wiring. I am having a problem with the braking system, which I am beginning to suspect has something to do with the ABS. There was a very audible groan (not a pad squeak) upon moderate braking that seems to be more prevalent on hard braking. I inspected the brakes. The calipers were in good shape, but the rotors seemed thin. I ended up replacing the rotors and pads on all four wheels. The brakes now seem perfect on light (normal) braking, with a nice high pedal. However, this did lessen - but not completely eliminate the groan on moderate to hard braking. There is no obvious indication of a hydraulic problem (no fluid loss, no warning light, etc). The only system I'm not familiar with is the ABS. My Haynes book isn't very helpful in troubleshooting this system. Can anyone share any useful tips as to how to diagnose the ABS or eliminate this problem?

The pads may be too hard/soft. did you dismantle the calipers, or just look at them? You may have a sticky piston/similar. It might also be a suspension noise? NB old flexible hoses should be replaced. They can and do stretch-even rupture eventually.

I didn't dismantle the calipers. The pistons moved easily on all of them. The rubber boots were in good shape. The noise was present with the old pads and rotors. The new pads and rotors lessened the problem, but the noise is still there. It doesn't sound like a typical Volvo brake squeal. The sound is more harmonic and deeper - more like a groan (if that makes sense). I can't seem to isolate it to any particular brake in either the front or rear.

I never though of it, but it could be the suspension. The car sat for quite a while before I bought it and returned it to the road. Is there a particular suspension part you were thinking of? I did replace the rear shocks when I did the brakes.

It is a sound I've never heard in Volvo brakes before, and in the past I've worked on many Volvo brakes from earlier 140's and 240's. However, I've never worked on a 240 with ABS before. It's just a feeling, but the sound can almost be described as a caliper that's loosening up grip as pressure is applied. I haven't found another post that quite fits my problem. It doesn't affect the stopping of the car in any way. But, I get stares from other drivers when it occurs. Is there somewhere to get info on the 240 ABS system?