Hey all, I've been putting some miles on my car preparing for a big trip and have run into an issue. I'm hoping someone might have an idea

Details of the car. '71 with a 6 swap. When doing the swap I also swapped to 911 struts and am using new "Ultimate M" aluminum Brembo calipers.

Rears are stock calipers. Porterfield pads all around. Everything has about 350miles



The issue:

The brakes seem to sieze up on their own. Left home and all was fine, 20 minutes on the highway. Exited and noticed they were grabbing a little, a couple stoplights later and I felt I needed to pull off, by the time I made it to a spot it felt like the hand brake was on.

After sitting for a few minutes it seemed to release a bit.

Check the gap on the e-brake. If not big enough, with heat swell they can drag.

I had that problem with the right front wheel of a VW. The problem turned out to be a deteriorated brake hose. The pressure would go through the line and activate the brake but the pressure would not release back through the hose. Replaced the line and everything returned to normal. I would determine which wheel or wheels is causing the problem and go from there.

If it's all wheels, check your pedal adjustment. I've seen too many folks adjust the rod from foot pedal to MC way to tight. What happens is your brakes don't get a change to quickly release pressure = the more you drive, the snugger they get.

Even if one hose is found to be the culprit, it's likely time to replace them all.

Usually a bad flexible brake hose. By now, probably more than one.

I had a sticky brake pedal, on one ,,at RRC--used a bungy cord to pull it back 100%,,went on the drives and drove Home..

It can be caliper adjustment, swelled hose or pedal rod too tight.....
On older cars the most likely is hoses and good policy to change anyway.

+1 on the adjustment at the pedal. That was the issue with mine.

Thanks for the reply all, for the pedal rod what is the proper adjustment technique?

Get down there with your hands and flashlight:

Make sure pedal returns easily 100% back to resting position
Grab the rod, should be roughly 1/8" play moving back and forth

If no play (snug or tight), there is a lock nut you can loosen. Just turn the rod back in a little.

Others will probably chime in with - should be XMM of play, just about an 1/8" will be fine.

Sounds good. I'll adjust tonight and try it out tomorrow.

Regarding the rubber brake hoses, they were relatively new, maybe 3-4 years and 4,000 miles, but I 2-day shipped a new set of ATE rubber hoses and will install them before the big trip.

Pedal rod was fine. I was texting with Eric and he said sounds like a pad venting clearance issue.

Pulled the driver side wheel and pads were rubbing the rotor, adjusted them out and all is well.

Pulled the passenger side and pads were also rubbing, but I can't adjust them out any further. The outer adjuster screw just turns and turns. If I go CCW on the outer I can push the piston out closer to the rotor, but I can't get it all the way in.

Same with the inner adjuster. When pulling the piston in/retracting it it gets to a point where the adjuster just gets stiff. I don't want to put much force on it and potentially strip the 4mm...


These were all adjusted to .006 when I put the pads in. Axles were only torqued to 150lbft then though, got them up to 250 when I got it to the shop.

Well I got the inner adjuster set, but now the outer adjuster has lost all connection to the piston, it won't move it in or out.

Click to view attachment

I found this while researching other stuff, thought maybe it could help someone else some day.

Again, this was not my problem. Seems as if my issue is caused by my adjusters.

Thanks, keep us updated with your progress

Maybe a peak at the parts will help, here is a write up

http://www.914world.com/bbs2/index.php?showtopic=90625

Yeah I had been referencing that thread. Just now I read further on and Eric makes a point on post #24 that he also texted me last night. It's possible the mechanism is seized to the adjuster and just spinning inside the piston. He gave the suggestion of an air ratchet in the counter clockwise direction, a few blips to get it free.

I don't have air tools but it gives me a direction.

I hope you get it straightened out for your trip.

@Optimusglen

Well I have a line on a pair of fresh remanufactured calipers that I'll pick up next week. Also all new soft lines since I'm going to have to bleed the whole thing again anyway.

The rear calipers are the only thing in my system that isn't new, they're original to the car and I rebuilt them a few years back. I want to be confident in whatever I drive cross country and trying to coerce my calipers to work properly isn't confidence building.

There are typically three things that can produce those symptoms. The swelling of the rubber lines internally pinches off free fluid flow; but this is usually just one caliper at a time. A leaking master cylinder can allow fluid into the pedal cluster causing the plastic bushings to swell and the brake pedal does not fully return and causes the master cylinder to be partially activated; toeing the brake pedal back is a quick fix, and a good diagnosis tell. Seizing rear calipers will be difficult to adjust, and the pistons do not retract properly which keeps the pads applied; normally this will only affect one caliper at a time. Fronts will also seize with the same effect, but there are no adjusters to help diagnose. Pedal free play can be an issue, but rarely happens unless you have assembled them wrong.