I put a new brake junction block on my 1980 242 DL about 2 years ago. Recently the red warning light comes on when I am sitting at a stop sign with the brakes applied over a sustained time. After I take off and jab the brakes a bit, the light goes off. The brakes still seem to work well. There is no fluid loss from the master cylinder. When I looked at the sensor on the junction block, it has a bit of fluid that seems to well up when the brakes are applied. Please advise.