Alright so for a while now, mostly as it gets colder it seems, I've been having breaking trouble. When I go to apply the brakes and the pedal is extremely stiff, then with steady pressure, it all the sudden sinks to the floor and is soft and takes all of the pedal's range to apply good braking force. Any opinions are valued.

 

Stiff pedal probably is from a vac assist issue, but settling pedal I think would be master cylinder.

Loose vac pump *or* alternator belt and leaking brake master cylinder seals? Maybe vacuum leak and M/C?

 

Hi, The stiff pedal is probably a vacuum issue,vacuum pump,vacuum leak,power brake booster diagram leak.
Going all the way to the floor is most likely the master cylinder. You can get a new power brake booster w/ master cylinder.

 

I forgot to mention quite a bit of info here, sorry. My vacuum pump is not quite a year old, all my brakes are practically new, soft lines all appear good and soft like they should be, no leaks or brittleness, no other fluid leaks, and the real kicker... I just replaced my brake booster and master cylinder 2 1/2 months ago because my brakes went out on the way down my driveway and let's just say I'm lucky to be here today cause it was a "slightly" close call.

 

Once in a while "New" parts are bad right out of the box.I know that doesn't help much but true.

 

I won't deny that a bit, just hope it's not the case here I guess. I had the old man help me out earlier and we bled the brakes all out. I refilled my reservoir, checked all the lines, and went over and made sure all my vacuum line were good and sealing properly. I haven't gotten to test drive yet, but we'll see what happens.

 

Well, i got to drive the truck this morning and it's still the same I used the self adjusters pretty hard on the rears and it stiffened up some but the pedal has always been a little spongy, im not concerned about that. I discovered that the stiffness and hard pedal at first only occurs when I'm at an idle or coasting, which is pretty much every time you wanna stop right? I put the truck in neutral, idled it and pushed the pedal to it being extremely stiff. Then I throttle it up a little and tries again and it works perfectly, so I guess the question is why would I have poor vacuum at low rpm cause that's gotta be my cause..?

 

Weak vacuum pump would be the prime suspect. Or possibly a vacuum leak, minor enough that higher RPM would overcome it and provide enough vacuum.

 

I have an analog vacuum gauge I'm going to hook up to watch it a bit and see what happens. Like I said my vacuum pump is practically new because my old one completely decimated itself. I'm thinking leak, but like I said, I checked all the lines so unless it's just extremely small and undetectable...

 

So remind us, since your truck is a transplant, are you on v-belts or serpentine?

 

Still running v belts. And my truck has factory a/c so my vacuum pump is under the alternator and driven by the belt off of it, not up top like some I've seen.

 

That's the same location for A/C and non-A/C trucks with V-belts (at least my '85, v-belts, no-A/C has it there). So it has the double whammy of being driven "secondhand" off the alternator, and so if the oh-so-long alternator belt is slipping, both the alternator and the vac pump suffer. And that alt belt can be a B!!!!!!CH to get tight. If it looks like the alt belt is loose, FIRST loosen the vac pump belt, THEN tighten the alt belt, THEN tighten the vac pump belt again. If I recall, the vac pump bracket has a square hole in it, that you can put a breaker bar in as a lever to hold the pump in place as you tighten the slider bolt (easier with an assistant).

 

Okay, I wasn't sure about that one. I've seen vacuum pumps mounted on top where an a/c compressor would be when none was present in pictures so I just assumed that's where they were mounted if the truck had no a/c. I didn't really consider this, but I installed a new alternator belt a while back cause mine shredded. Do you think the belt might be stretching and has gotten to the point where it's starting to slip?

 

^^^^^ I THINK that's just the serpentine ones.

After any v-belt replacement, it's good to go back after a few miles and re-check tension.

 

Alright, I got ya now.

As for my belt, I did recheck and tighten once, but that's probably been the better part of three months or so now that I think about it so it's probably way over due to be checked again since it was a brand new belt.