Springs? Brake Fluid Reservoir Caps

[brookmp]

1982 W123 Turbo Diesel

I attempted to pressure bleed my brake system today and I suspect one of the small sensor seal caps on top of the reservoir is leaking. Neither of the two caps have any visible cracks, but when I started to pump up the pressure, a little brake fluid started to seep from one of the caps and I couldn't get any pressure to build up. No other visible leaks anywhere else.

When I removed both caps to inspect them, I noticed that the cap closest to the windshield has a spring under it, giving it resistance. But, the other cap, closest to the front of the car does not have one. I searched and searched online to see if I could verify whether both caps are supposed to have springs, but came up with nothing.

My two questions are:

1. Did both caps on top of the reservoir come with springs from the factory?

2. Even though both caps don't have visible cracks, are they the weakest links that are likely causing the inability to pump air into the reservoir (there was slight seepage from the forward cap without the spring)?

Thanks for addressing either (or both) of my questions.

Brook