So, this has happened in the past once or twice.
Happened 2x yesterday, I had the truck in 4lo to pull a car back onto the road (it was hanging off the edge of the road almost over a large drop off) after pulling the car to safety I lost brakes. The peddle became very hard and I heard hissing. Popped the hood and where the vacuum line goes into the break booster had popped out. Plugged it back in and everything was fine.

This morning went to go to work, started the truck and BOOM it popped the line a 2nd time.

What could be causing this?

Everything works fine most of the time.

thoughts, anyone else have this issue in the past?

Maybe jut over the years they have lost there ability to grip and hold on, have you tried using a band clamp or maybe even replacing that piece of vac hose? Just my 2 cents

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Black 2008 ranger sport 4.0 SOHC SAS'd and converted to 4x4 riding on a Dana 50 up front and a sterling 10.50 in the rear regeared with 5.13's, mickey thompson classic 3's rapped in 37x12.50 maxxis creepy crawlers

I was about to say

you could try replacing the line so it will grab on better

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95 Ranger XLT 4x2 2.3 I4 5 speed 206,000 *dead*
96 Ranger XLT 4x4 4.0 V6 5 speed 173,000 *alive*
D35 front, 8.8 rear, 3.73 gears, limited slip rear diff

Hose clamp

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2021 F150 5.0 Screw

Past:18 F150 2.7, 16 F150 5.0, 14 F150 5.0, 07 F150 5.4, 03 Ranger 4.0

Master Certified Ford Parts / Warranty Admin

It is the plastic nipple that goes into the rubber grommet. Perhaps a new rubber grommet is to be gotten...
I was thinking the same thing, I do have a clamp on the hose that attaches to the plastic "L" part.
Thanks guys! Will let you know how it goes

Got a new check valve and rubber grommet from NAPA for $9
Problem solved.