Brakes Locked

[peller]

This may be a simple question, but I wanted to run it past the group.

Working on a 68 280sl that's been garaged for several years. After working on an unrelated differential leak, I took the car out for a spin. After a quick stop at the local convenience store, I proceeded to back out of the parking space. After backing out, I attempted to proceed out of the car park, but noticed that the brakes appeared to be locked up. The brake peddle had little resistance the top half way down, but did have resistance the remaining way to the floor. I then pulled back into the parking spot, with much wheel resistance and parked again. I then called the wife and headed home to get my tools. When I returned, approximately 20 minutes or so, I thought I would check the brakes again. This time all was well and working normally.

Checked fluids and there appears not to be a leak.

What should I check next? I am thinking its likely a sticky caliper, but wasn't sure with the weird lack of peddle resistance for the first half. That makes me think its a sticky master cylinder piston.

Thoughts on the cause and next course of action?

Thanks!

[stickandrudderman]

The search function is definitely under-utilised here!
It's likely to be a swollen brake hose.

[Cees Klumper]

Best to replace the four brake hoses, and also to 'exercise' the two pistons in each brake caliper (push into the caliper manually, apply brake, push back in, repeat a few times) to at least cover that side of the system. You can then see if the brake master cylinder needs anything.

[peller]

Thanks guys, I'll start with the brake lines.