Brakes Brakes drag when warm. How to diagnose?

Noobz347 said:

Or maybe the pressure relief for the pedal?


Thought: What if you restricted the vacuum line going to the booster as an experiment?

Click to expand...

Does restricted equal disconnected? Also how would I go about testing that pressure relief valve on the brake pedal? Isn't that the way the cruise control knows to let go? If so, I can say that the cruise control shuts itself off when any breaks are applied.

Caveat up front: I have twice convinced myself that I did something that eliminated the brake dragging problem only to realize after more driving that it was still there. Anyways, I've disconnected the booster from the vacuum tree and plugged the tree and the hose. It obviously takes a lot of pedal effort now, but I did not get any brake drag on the 30 min drive to work, this morning. I think we're on to something...

So, absolutely no drag on the way home. Then, I talked to Northracecars.com about it, and he suspected the prop rod needed more adjustment, but after listening more thought maybe booster issue or MC sticking. lol... I get it... it's very confusing, especially with the intermittent-ness.

Clues:
1. Typically drags somewhere between 5-15 min into a drive and clears up on the highway
2. Can be reset or cleared up with a heavy linelock brake release
3. Does not happen when booster is disconnected

New clue:
Turned the booster rod in a lot (maybe another turn) & reconnected vacuum. Didn't make it half a block before noticing drag. Pulled MC out from booster to turn the rod all the way in, i.e. no adjustment is left, and noticed this grease squeezing past the inner part of the rod. hmmm

On the next test drive, I noticed absolutely no difference in where the pedal engages. How is that mechanically possible? If there's more of a gap between booster rod and MC plunger, there has to be more pedal before engagement, but there simply is not. But... I couldn't say for sure if there was any drag.




I'm getting ititis, at this point. I have a spare 93 Cobra booster on the shelf. If I also have another 93 Cobra MC, I'm gonna replace both this weekend, and if not then I'll order and replace both soon.

Black Jack has consistently been a car that likes to come up with some tricky ones for me (compound drivetrain vibration I had to go through absolutely everything to fix, intermittent spark issues that turned out to be a dying MSD box I couldn't easily bypass, thanks to the then-recent wire tuck, to name the two big things). It is just the fox I needed to challenge myself and learn new things, I guess. At least it has been reliable and held together with an old high mileage powertrain on a 150-shot to this point. *Knocks on wood*

Still had definite brake drag this morning, despite the rod being turned all the way in to the booster as far as it could go. The booster's services are no longer required, and it is disconnected permanently until I replace it with another one. Hopefully I'll get around to it this weekend.

Yeah, I can't say I understand it. I'll watch the video after work, and hopefully something will make some sense. But, I know I'd rather drive with mechanical brakes indefinitely than drive with them dragging like they have been. After I disconnected it about 5 minutes into my drive, it didn't drag the rest of the 25 minutes into work.