RG5384,

Check your flexible brake lines. They run on each wheel from the solid brake line to the caliper. When these begin to fail it almost always starts as swelling on the inside that constricts the flow. You can easily push fluid in to the caliper but the pressure doesn't release easily so the caliper appears to be sticking slightly. These are cheap and easy to replace so if they are at all hard and stiff I'd replace them first. It's also a good excuse to bleed all the brakes properly.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold