Brake problem W126

I have an intermittent problem with braking on my '91 350SDL. Very hard peddle usually on second application after start up, and then usually only after brake application from reverse. This first appeared after the last
major service... lasted about two weeks then went away. Just started again day before yesterday ( 6 weeks since major ). Has not occurred more than one time in each run cycle, and as I said is intermittent even then. Did it twice yesterday ( 1st in AM, 2nd at lunch...but not at days end ) and did not do it this AM. I found with the previous incidence that if I did not apply brake to stop rear motion ( backing out of driveway ) first, the hard peddle did not happen. Vehicle will stop, but its scary to think it may happen in a panic-stop situation, as it requires a great deal of leg strength to apply peddle when this happens.
What do you think? Air bubble? Cylinder failing? I'd like your opinion before it heads to the shop.
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I think that main vacuum hose to your brake booster is failing... most likely cracking at the checkvalve. My snapped and I completely loss my power brake... Like you said... extremely hard to stop the car.
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hehehehehehe ... Hey Tiger !!! Do you have michelins on that car that is hard to stop? hehehehehehehehehehe
mcbrue teasingly under the bridge in the trailer down by the river
96 S420
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No... that was not Michelin... But I do have Michelin on my Diesel now... and they are not that great... too squirrelly around bends... my car runs all over the road.
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