I am having an issue with my 92 s10 blazer that I cant figure out. I few days ago I started my truck and noticed that it was idling really rough. It was surging slightly but the real problem is that I have lost 85% of my brake pressure. The truck still stops but it is not really safe to drive. I have checked all of the vacuum lines and I cant find anything (visually anyways...) Is there anything that you guys can think of to check or a different way to find the leak?

What was strange is that everything was fine one day, when I shut the truck off the night before and, acting crazy the following morning.

From what I understand, it would have to be a significant vacuum leak to effect the brake system.

Thank you all in advance, I don't know what else to do.

 

I am pretty sure that it is the brake booster. I will do one more check and then change it out. I will let you guys know what I find.

 

I replaced the brake booster and it is still doing the same thing. I have looked for a vacuum leak but have not been able to see anything. I used smoke to try to find the vacuum leak and there was no sign of any smoke leaking in the engine compartment. If any of you have any ideas please let me know, I am not taking this thing to a shop.
Thank you all in advance!!