Need Help Diagnosing Braking Issue!

Hey everyone, I took my 2007 offroading a few weeks back and absolutely thrashed it through the mud and whoops, and afterwards I realized that my brake pedal was requiring more pressure to stop the truck, basically going all the way to the floor. I went through a whole laundry list of things and threw a new ABS modual at it in hopes of just getting lucky but had no luck. When I brake hard and fast, there is a hissing noise that comes from somewhere in the engine bay... if it is a vaccum leak I can't seem to find it but it sounds like it came from back of engine or near ABS modual, maybe even from within the brake lines. I checked all of the vaccum lines, to my knowledge, that exist in that area and in other areas, checked all the brake lines, no leaks and no change in level in master cylinder reservoir, bled the brakes, replaced the ABS modual, bled them again, and overall just put a lot of time into trying to diagnose this. Is there something that I am missing? Thanks!

 

Sounds like the vacuum brake booster is failing.

 

The only reason I haven't replaced that yet is because the hissing noise doesn't come from that area, but it could very well be that and it does fit the problems I'm having... I'll definitely check it thanks!

 

In case this helps (from FSM)

 

Usually a low brake pedal is a bad master or low fluid. A hard pedal is a booster issue, maybe lack or loss of vacuum. A hissing noise is usually a vacuum leak. Before shooting the parts cannon at it you can make a smoke tester at home with basic items like a jar, soldering iron and rags. There are plenty of "how to" videos on You Tube. That will show you any vacuum leaks. I had a bad booster and my pedal would get progressively harder to press and would eventually lock up the brakes without even pressing the pedal. Does the pedal go back to normal if you disconnect and then reconnect the vacuum line running to it? That would always "reset" mine for a short period.