Best way to test brake line restriction??

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DanteGTZ
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Best way to test brake line restriction??

Postby DanteGTZ » Sun Oct 23, 2016 6:17 pm

For a while now I had thought that my driver side rear wheel cylinder on my Quasar GTZ was having problems. It was not uncommon for the rear brake to lock up on gravel when barely applying the brakes. I hadn't investigated it much because I was planning on swapping to rear disc brakes. Well, this past weekend I finally got the rear disc setup all swapped over and have noticed that my issue has remained - When I bled the brakes (with the wheel off) I saw that the caliper just didn't seem to move as much as the other side when the pedal was depressed. Same thing with bleeding it - it just felt like something wasn't quite right.

Took the car for its first drive with the new brakes and the rear caliper was definitely sticking. To be clear, it is NOT an alignment issue with the brake parts. It appears to be something either in the master cylinder, ABS module or the line itself that is not allowing proper fluid movement/pressure. The lines are not rusty and the fluid is new/clear. Any ideas where to start before I waste a bunch of time guessing?


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1993 Garnet Quad4 GTZ - GTZed-Eh? - SOLD
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Re: Best way to test brake line restriction??

Postby 1988GTU » Sun Oct 23, 2016 7:33 pm

Your soft line going from chassis to rear axle is my guess. Replace it.


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Re: Best way to test brake line restriction??

Postby 1988GTU » Sun Oct 23, 2016 7:35 pm

ACDelco 18J2268 or 1761006


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Re: Best way to test brake line restriction??

Postby DanteGTZ » Sun Oct 23, 2016 8:57 pm

Oops - I failed to mention a critical detail. The rubber hose is long gone; replaced with a braided SS line between the hard line and caliper.


1993 Quasar Quad4 GTZ - Project WTF
1993 Garnet Quad4 GTZ - GTZed-Eh? - SOLD
1993 Aqua GT - 3.1 / 5 speed - 82k original miles - SOLD

Previous Berettas: 1990 GT and 1993 Quasar GTZ

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Re: Best way to test brake line restriction??

Postby 1988GTU » Mon Oct 24, 2016 3:17 am

Have you pulled a vacuum at that wheel using a bleeder pump (mighty vac) ?

If you can, try attaching the bleeder to the line to use the bleeder pump in the engine bay segregating the abs/master from the system. You will need to detach the line from the unit and crack open the port on the caliper.

I suspect the ABS having a blocked port.


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Re: Best way to test brake line restriction??

Postby 3X00-Modified » Tue Oct 25, 2016 6:39 am

Yeah you need to pull apart the master and abs unit... If it scares you put it in a box and send it my way, I've ripped them completely apart before. Second to that you can remove that line and pressurize it with a compressor to hopefully dislodge whatever is blocking flow. Also do a full visual check for any possible kinks.

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Re: Best way to test brake line restriction??

Postby ifixalot » Tue Oct 25, 2016 10:02 am

Have you inspected the brake lines for any dents from road debris?
I had to repair the fuel line on our Saturn because we rolled over something that shot up
and cut the line. It's not hard to imagine something denting the brake line.



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Re: Best way to test brake line restriction??

Postby DanteGTZ » Tue Oct 25, 2016 10:27 pm

The line looks physically fine from end to end. No rust or corrosion on it anywhere. I guess I'll pull the line and try some air. Wouldn't surprise me if the ABS has a problem, especially considering how long the car has sat at times over the years. As far as the ABS/master setup - I've removed an ABS module before (to get a master from another car) but I've never torn into one...

As for the master, I've taken a few apart and cleaned them, but that's about it. Ultimately I'd like to figure out which master I need to go with since I've now got the Wilwoods up front and the Neon discs in the rear. I have a ~1993 Lumina Z34 (w/ABS and 4w disc) master on the shelf which I was originally going to swap in but IIRC, last time we talked you might have said that it wouldn't be a good match...?


1993 Quasar Quad4 GTZ - Project WTF
1993 Garnet Quad4 GTZ - GTZed-Eh? - SOLD
1993 Aqua GT - 3.1 / 5 speed - 82k original miles - SOLD

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Re: Best way to test brake line restriction??

Postby 3X00-Modified » Wed Oct 26, 2016 11:45 am

That will be an ok match, You will have VERY little pedal travel because the Willwoods are very small volume wise in comparison to say a Lumina caliper or even the stock Beretta one, equates to very touchy brakes... I believe Tyler has the same bore master on his Willwoods and I know they are very sensitive... almost too sensitive for my taste. If the threads and valves are the same size tho, you could just swap out the proportioning setup that is on the outlets.... That should fix the f/r difference which is honestly all you need to change if your pedal currently feels ok.




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