Andy,

Had the same prob when I changed a stuck caliper on an '83 242, also had the prob on the 140s in the old days.

Bet your bleeding is fine.

Familiar w/ "pressure differential warning valve"? Is up front, left somewhere. Is supposed to trigger warning light once the master cylinder goes low in one of the two circuits. A pressure controlled switch/plunger thingy.

On the 140s the "business" part of the valve that sets off the light would unscrew; once you had this out, upon replacement the valve would "reset" and the light would go off.

I remember calling the dealer years ago when I had the 242 and he said to follow the same procedure on the 240. But when I was under there, it seemed to me the switching part was not intended to be removed, there wasn't even a hex on it.

Memory's foggy, that car was a rustbucket and maybe I just didn't pay enough attention. In my case, I put black tape over the warning light as the car was headed for the crusher soon anyway.

Check into this further: I'm sure others have been down the same road and might have better memories.