If you replace the caliper here's a Brake Tip I toss in at every opportunity:

You can prevent Master Cylinder Brake Fluid Loss from any/all open brake line(s) by blocking the brake pedal depressed before you start. It only takes an inch or two on the 240s. The MC pistons will block the reservoir ports, so no fluid will drain. But you will need to do a quick bleed on the new caliper after it's installed.

>>Disconnect the battery or pull fuse #7 to keep brake lights off while the pedal prop is in place.<<

I've been using this on '80s 240s for more than 10 years now—ever since I learned it from an independent Volvo specialist. I made a wooden prop that hooks to the bottom edge of the pedal and bears against the 240 seat adjuster bar. It's handy for checking brake lights too.

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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.