Smoking brakes (Page 1/1)
curt JUL 16, 10:53 AM
Ok, I've read quite a bit on the subject and have some context but I'm not sure the previous posts get close enough to what I just experienced.

I have an '85 GT that had foot-to-the-floor brakes that caused some white-knuckle moments. Replaced the MC and bled the system. No improvement. Replaced the check valve for fun. Decided to put in the S10 booster. The first few test drives were around the block so as to not get stranded or hit anything if something went wrong. Yesterday, I drove it 2 miles one way. Backing out the car didn't seem to want to roll but I couldn't determine if this was due to the pistons adjusting or not.

It's fair to note that I'm not a brakes beginner. So I had reasonable expectations and practical experience with braking "quirks" that happen after the system is opened/replaced/repaired.

I had fantastic, better-than-stock pedal performance the way out. I stopped for 20 minutes to grab some items from a store and left to come back home. The pedal was stiffer than before and it felt like the calipers weren't releasing. The vehicle didn't want to roll. 1/2 mile later and all four wheels are now smoking and I wasn't able to depress the pedal whatsoever. No worries, the car wanted to stop. Calipers feel locked but this feels like pressure related.

Before I start ripping out lines, has anyone run into this before? Remember, this is all four wheels smoking and ready to catch fire. So if it's rubber hoses, it's all of them at once. Leads me to believe it's something under the hood rather than at the wheel but again would like to hear if anyone else has run into this before I open the system again.
theogre JUL 16, 01:16 PM
Loosen MC mounting bolts to the booster.
If caliper(s) release now then you F'ed up the "Booster upgrade" and MC doesn't return to full rest w/ no load on the pistons.

replacing MC etc and tighten pipe fittings too much will crush the flares and you get little to no flow. May have some flow when you push the pedal same as crap hoses often do.

------------------
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curt JUL 16, 01:25 PM

quote
Originally posted by theogre:

Loosen MC mounting bolts to the booster.
If caliper(s) release now then you F'ed up the "Booster upgrade" and MC doesn't return to full rest w/ no load on the pistons.

replacing MC etc and tighten pipe fittings too much will crush the flares and you get little to no flow. May have some flow when you push the pedal same as crap hoses often do.




Hah, fair enough but how do you screw up a booster install?
Crasian JUL 16, 03:23 PM
My experience with a newer booster went wrong.. I got a later model S10 brake booster, I assumed they all were the same, but they weren’t. The internal activating pushrod (it was a large plastic piece) was about 1/16” too long. That in turn put constant pressure on the brakes and as the brakes heated up it would lock up all the calipers. I had to machine the rod down some to get the clearance I needed. We’re you having the same problem before and after the booster upgrade??

-Crasian
curt JUL 16, 04:25 PM

quote
Originally posted by Crasian:

My experience with a newer booster went wrong.. I got a later model S10 brake booster, I assumed they all were the same, but they weren’t. The internal activating pushrod (it was a large plastic piece) was about 1/16” too long. That in turn put constant pressure on the brakes and as the brakes heated up it would lock up all the calipers. I had to machine the rod down some to get the clearance I needed. We’re you having the same problem before and after the booster upgrade??

-Crasian



This is exactly what my thoughts were. Once pressure builds in the booster, it just doesn't fit. No, to answer your question, I have the opposite problem. Prior to the booster upgrade, I had no brake pressure, fade, etc. Stopping the car involved putting it in neutral, two-footing the brake pedal and being creative or just not driving it. After, the calipers are all locked after a short trip. How did you determine how much you needed to remove from the pushrod? Did you get any pictures for comparison?
theogre JUL 16, 04:39 PM

quote
Originally posted by curt:
No, to answer your question, I have the opposite problem. Prior to the booster upgrade, I had no brake pressure, fade, etc. Stopping the car involved putting it in neutral, two-footing the brake pedal and being creative or just not driving it.

You had:
Bad booster,
Problems w/ Vacuum to run it.
or Both.

Vac problems can still piss off the new booster in the same way but not cause the new issue.

See any FSM on the booster install or use search here.
Crasian JUL 17, 11:11 PM
To answer your question about the piston rod thingy, no, I unfortunately did not game any pics of it. But I could feel as I bolt the master cylinder down it was being pushed. I have a lathe and simply turned down the top portion to shorten it some. I then used modeling clay on the tip of the plastic rod and made sure I had some clearance. Not very precise nor scientific but it got the job done well enough.
-Crasian