All 4 brakes lock up and won't release pressure?!?!, what could be holding the pressure? Options

[Kevins911]

5 years on jack stands and I take it out for the second drive today and the brake system seems to build up pressure and not release it.

new 19mm MC
new PMB rear calipers properly adjusted
rebuilt front calipers
new SS flex lines
new front hard lines

blead with a motive power bleader twice. The brakes work great but after only a few miles of driving the pedal gets firmer and firmer untill the brakes are fully locked up, and the pressure won't release and the car wont move. I cracked the front left bleed nipple to let the pressure off and limped home using mostly the hand brake. Any ideas where I should start?

Thanks
Kevin

[Mike Bellis]

Master Cylinder

[Cap'n Krusty]

Adjust the brake pushrod between the pedal and the master cylinder. Give it a few thousandths clearance, say 10-15, maybe a little more,cold. You might also want to get rid of those POS SS braided teflon brake hoses. If not now, at least at the 10th or 12th required monthly inspection.

The Cap'n

[Kevins911]

Thanks, I'll adjust the push rod. I did a bunch of reading on the brakes prior to posting this and came across the SS brake line info...there on the "to change" list, especially for a street car.

Cheers
Kevin

[realred914]

Thanks, I'll adjust the push rod. I did a bunch of reading on the brakes prior to posting this and came across the SS brake line info...there on the "to change" list, especially for a street car.

Cheers
Kevin

Stainless wrapped teflon is hardly piece of shit brake hose, Me and 914 friends have safely enjoyed them for many many many years. just install them carefully like, make sure they wont twist or bend sharply under suspension travel and wheel turning and you will be fine. if your extra anal, get the DOT approved stainless lines, they have a plastic strain relief on the ends.

likely master is not venting back, push rod too long is one possibility (it has to be able to freely move all the way back when you let off the pedel.) dirty clogged up junk in the master is other possibility, (maybe junk from a dirty resivoir? seeing as the master is new)

for sure the stainless/Teflon hoses are not the probelm, they dont swell like shitty stock rubber hoses do. after the umptenth time checking the rubber hoses for swelling and the brake drag induce by swelling, you tire of them. Change out a brake caliper that failed as in cooked do to over heating becuase the rubber line swelled, and you wont ever want them again.


good luck

[ME733]

Thanks, I'll adjust the push rod. I did a bunch of reading on the brakes prior to posting this and came across the SS brake line info...there on the "to change" list, especially for a street car.

Cheers
Kevin

Stainless wrapped teflon is hardly piece of shit brake hose, Me and 914 friends have safely enjoyed them for many many many years. just install them carefully like, make sure they wont twist or bend sharply under suspension travel and wheel turning and you will be fine. if your extra anal, get the DOT approved stainless lines, they have a plastic strain relief on the ends.

likely master is not venting back, push rod too long is one possibility (it has to be able to freely move all the way back when you let off the pedel.) dirty clogged up junk in the master is other possibility, (maybe junk from a dirty resivoir? seeing as the master is new)

for sure the stainless/Teflon hoses are not the probelm, they dont swell like shitty stock rubber hoses do. after the umptenth time checking the rubber hoses for swelling and the brake drag induce by swelling, you tire of them. Change out a brake caliper that failed as in cooked do to over heating becuase the rubber line swelled, and you wont ever want them again.


good luck

.........I agree completely. And your explainations are right on. Excellent comment in my opinion.

[DBCooper]

Teflon lines won't tolerate kinking, so don't let the calipers dangle when you're working on a wheel and avoid like the plague any shop that works that way. That and being able to identify a hose that's been mistreated like that are the weaknesses of teflon lines. If they aren't misused they perform better than rubber lines, and are longer lasting too.

Sorry Krusty, total respect, but it's true.

[charliew]

Like others I would suspect the pedal rod is too long, keeping the mc piston from coming back far enough to release the pressure from the last pump, I think the port is called a compensation port to let the pressure off. I once had to adjust the rod in a bug on the side of a very busy 4 lane road at lunchtime in a suit. Braided stainless is my first choice if it is available. They have been on two of my fieros for several years. I wish I could find some for a polaris 4 wheeler I have.

[Kevins911]

It was the push rod, thanks everyone