#1  
Old 08-12-2021, 12:53 PM
73LeMans's Avatar
73LeMans 73LeMans is online now
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Default What's the hold up?

Both front brake calipers are locked up - hoping to figure out why before I start swapping parts.

All parts have about 300 miles on them, except the line lock and the flex hose. Both of those are many years old. (13 years?)

- Right Stuff Booster
- Wilwood Master Cylinder
- Wilwood prop valve
- Biondo line lock
- All new hard lines
- Steel braided flex hoses
- Wilwood D52 Calipers



In the 7 hours of drive time since being assembled, brakes have been excellent with no deviation.

Last Sunday however, I went to an event and as I drove up to the stop light, I could feel the brakes harden up and it took a lot of pedal effort to stop. Didn't think anything of it - it seemed to brake fine for the mile to the event and the mile back to the trailer after that. I could see at the show (no hood or fenderwells) the brake rotors were discolored.



At the time I thought it might just be normal use.

When I got the car home, I used the line lock for the 4th time since being back on the road and did a small burnout after rolling off the trailer. (because I'm a child)



Drove the car into the garage and two days later, when I went to swap front wheels, I noticed both wheels were extremely hard to rotate.

To troubleshoot, I've done the following:

- Pulled the brake pedal up - no difference (it didn't move)
- Removed a caliper to verify the wheel spins freely - it does
- Reset caliper pistons, put it back on and verified wheel still spun freely.
- Applied the brake (car not running) and from that point forward, that rotor was again, very tough to turn by hand - almost locked.
- Disconnected the brake pedal from the pedal rod - no difference
- Pulled back on rod from inside car in case it was applying pressure - no difference
- Separated the M/C from the booster in case the rod was stuck and still applying pressure - no difference
- Still while separated, I reconnected the pedal and verified rod movement was free and smooth
- Cracked open the bleeder on a caliper and spun rotor - no difference. Still locked

Both rotors look to be the same off-color. It doesn't appear its more one side or the other and both are equally tough to rotate. There are no bent lines or crushed flex lines. The rear wheels spin just fine. When I removed the master cylinder from the booster, it appeared the cylinder was in its proper position of rest again the retaining clip in the back of the unit.

Operation of the line lock (Biondo unit) appears to be in order. The solenoid makes all the right sounds and worked fine when I rolled the car off the trailer.

I banged on the case with a ratchet just in case something was stuck, but it made no difference. I can rule out electricity holding the valve closed because my troubleshooting (except the checking of the solenoid) is all done with the master cutoff switch in the off position.

I've read these D52 Wilwood calipers get sticky - but both at the same time?



I saw no solution on how to keep them from getting sticky.

Im kinda stuck - see what I did there? - on next steps. Ideas?


I'm inclined to believe the biondo linelock is the culprit, given its age and the fact that it sat the last 6 years (2 without fluid) but I'm not 100% convinced. If I crack open the bleeders, thus eliminating and pressure exerted by the linelock, I would expect the rotor to then be easy to turn. They were still locked


Thoughts?

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  #2  
Old 08-12-2021, 01:12 PM
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leeklm leeklm is offline
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Default

"I'm inclined to believe the biondo linelock is the culprit, given its age and the fact that it sat the last 6 years"

Yes, I would bypass the line lock and go from there.

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  #3  
Old 08-12-2021, 01:58 PM
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hobbygto65 hobbygto65 is offline
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Default

If you cracked the bleeder on the caliper and it still does it its can't be the line lock because you just eliminated it. Sounds like either the pads are to thick or your calipers are sticking.

  #4  
Old 08-12-2021, 08:48 PM
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Sirrotica Sirrotica is online now
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You might want to see if you can stick a screwdriver blade between the rotor and brake pads and see if they can be retracted manually, one to check if the pads are too thick, and two to make sure the pistons still move into the caliper when force is applied.

The only other thing I can think of is caliper slides sticking, or they are made incorrectly stopping the caliper from sliding. New calipers shouldn't be prone to frozen pistons, but you never know with the quality of parts we get today.

If you can retract the pistons by prying them with a screwdriver, you need to verify the slides are able to move in and out.

As the above post states, opening the bleeders up eliminates the hydraulics malfunctioning.

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  #5  
Old 08-15-2021, 08:52 PM
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You guys got me thinking. I hadn't looked at the pads as a suspect. I had forgotten to tell you that the pistons did move freely back when I exerted pressure on them with my thumbs when the caliper was off. (The screwdriver trick was much easier on my thumbs FYI). I was running Powerstop's "Extreme" pads but I remembered I had some new Wilwood pads lying around, so I measured them. The Powerstops were .020" thicker on each pad surface than the Wilwoods. (.040" total) Its not a ton, but its something so I put the Wilwoods in. In the garage I could no longer replicate the problem. Step on the brake, let go and the wheels would still spin.

Today was a better test....some actual road driving to a local show. Not far (1.2 miles round trip) and the wheels are still free. I just checked. I'll keep an eye on it for longer drives, but I'm tempted to call this solved. Thanks for the assist!

__________________
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Mark S
.
Who needs nice and pretty, when you can have mean and nasty?
KRE Aluminum headed 463CID 73 LeMans. Used to run 10.6x @ 124.55. 3700lbs
.
So much for 2020...shootin for 9s in 2021...and in 2022 apparently.....looks like 2023 as well.
>>My 73 Build thread
  #6  
Old 08-15-2021, 10:01 PM
428goat 428goat is offline
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Default

Friend had the same problem. He finally changed both of his new flex hoses to another new set and then all was good.. something to think about.

  #7  
Old 08-15-2021, 10:47 PM
Goatracer1 Goatracer1 is offline
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If you opened the brake bleeder and the brake was still dragging it HAS to be a problem in the caliper or the pads. With the bleeder open there is NO pressure on the caliper piston. The piston or the pad is not retracting.

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