Brakes are stiff while driving.

Today while driving home, my brakes suddenly felt very stiff, not fully locked but still very hard to press.

After getting home I visually checked all the lines, but everything looked good. Then while the truck was running, I slammed down on the brake pedal as hard as I could. I felt a popping noise (air?) in the pedal and it felt as if it was back to normal. So then I took the truck for a spin, and the problem was back within 2 minutes of driving.

Any clues on what this could be? (sorry, not very mechanically inclined)

 

I haven't changed or added anything to my truck for about 6 months.

 

Power brake booster.

 

Earlier when searching, I found http://www.kondratyev.com/porsche/technical/body/vacuum_boost.htm

I did the #1 - #3 steps, but it wasn't fully stiff as when the truck is off. Also it isn't stiff after waiting 10 mins.

 

Any ideas?

 

Can you provide more info? Do you have ABS? Was it a gradual stiffness to the pedal?

 

Yes, I have ABS.

While the truck is off, I depress the brake pedal. After starting it up, the pedal slowly falls.

While the truck is on, whenever I pump the brakes I have resistance and its slow(not as much when the truck is off)

Also while randomly pumping the brakes, they sometimes feel 100% normal, but then go back to being shit on the next pump.

 

anyone?

 

Sounds like the vacuum line to the BB isn't connected. Check the line from the booster to your intake plenum. Depending on your intake to the throttle body something may have made it through and clogged your line.

Typically it will feel stiff as if the truck is off with no power.

 

Damn you; now I'm getting a gradual stiffness. It's just NOT in my brake pedal.

 

I believe you may have a faulty brake booster. It sounds more and more like it. My concern would be the POP you heard when you slammed on the brakes. It may be a slight internal rupture of the diaphram inside the booster. Not 100% sure of course, but doesn't sound good.

I disagree. If he starts the truck with his pedal pressed, and gets a gradual fade, that means his booster is engaging (at least to some degree) If he had no vacuum to the booster, it would remain a hard pedal at all times.

LMFAO

 

I tried disconnecting the vacuum hose that connects to the BB, then started the truck up.

It was a much different feeling, as I was getting no airflow at all. The feeling im getting is a slow pedal drop.

 

So even when you are holding the pedal, it continues to "fade" or drop down? Maybe I misunderstood what you were saying in your previous posts. If that is the case, look for a possible leak. If you cannot find a leak at all, then suspect a master cylinder.

I apologize if my misunderstanding of your description lead you in the wrong direction.

 

would it be smart to go ahead and replace the master cylinder, since its not hard or expensive, new brake fluid, and if its still doing it that would peg the BB

they all wear out over time, so its not like throwing money away.

 

Correct.

Though now when I press on the brake pedal, I also hear almost 'wheezing' sound from under the hood. (possible bb?)

 

Wheezing sound like a vacuum leak?

 

Possibly. I'm not sure where it would be leaking though.

 

Hmmm...

You say you haven't noticed any leaks, but what about the overall level of brake fluid in the master cylinder? Is it full to reasonably full or very low?

Check the rear drums and their condition/operation. Remove the drums, etc.

Couple reasons...

- On vehicles with drum brakes, much of the actual "pedal feel" comes from the rear brakes/drums.

- A wheel cylinder can/will leak and will not be the most obvous spot from just looking. It can coat everything inside there, making a big mess. Also a suspect here in the "popping" noise you heard.

- Rear drum issues will make a car brake incredibly oddly. And bad looking/sounding stuff to.

- Check that all interal drum brake hardware (springs, hold down pins, etc) are not missing or broken causing a reactionary problem where the shoe could jack against the inside of the drum.

 

Alright I misunderstood the issue also.

Have you done anything to your truck recently, like adding new or longer brake lines? If so that will make the pedal feel softer with the expansion of the braided lines. If not it does sound like you have a leak somewhere. If you have to keep adding brake fluid then it's a big sign it's dripping out. I've rarely heard of brake boosters going bad on yota's.

 

Waiting on OP at this point to give us an update. Kinda curious what happened.