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Leak at Brake Caliper bleed screw

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#1
Alberto

Alberto

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1st weekend of the year, I went out on new GLocs and rotors and calipers from a few years ago and a fresh bleed.  Pedal felt solid on day 1.  Felt softer at the end of the day.  I figured it just needed more bleeding so did that and it helped but not as perfect as day 1.  Lived with it for another weekend.

 

Last race, I loaded up the car, went home and noticed a huge puddle of brake fluid at the RR tire when I was unloading.  The RR caliper was leaking.  So I replaced them both rear calipers with Drago's fancy, sexy calipers.  While bleeding the brakes, I noticed wetness on one of the front calipers.  So I decided to test by pressurizing the brake system and check for any leaks.

 

Cleaned all the calipers with brake clean and paper towel.  Jammed the jack handle between the brake pedal and the seat effectively applying the brakes overnight.  Next day, I see telltale signs of leaking from 3 of the bleed screws.

 

Replaced the front bleed screws with those from a spare, good caliper and repeated the test.  Some leaking from 2 of the bleed screws...

 

Any thoughts on what I might be doing wrong with the bleed screws?  Anyone ever have something similar happen?

 

I usually just tighten the bleed screws with my tiny 8mm closed end wrench to 1 ugga.  Am I over tightening?  Does position of any orifices in the bleeder screw matter?

 

Contemplating trying some thread sealant from Speed Bleeders...

 

Thanks 


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#2
Alberto

Alberto

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The thread sealant seems to have worked.

 

On a side note, bleed screws vary in shape more than I imagined...

 

I have a bunch of spare calipers - most sourced from Mazda and a couple from random Miatas collected over the years.  So I removed the bleed screws from them and compared.  The butt end of the bleed screw is conical in shape - like a funnel.  It was interesting to see how the angle of the butt end of the screw differed.  The witness marks of where the butt end rubbed against whatever is at the end of the hole it threads into were wider on some - meaning a larger mating surface, I think... 

 

I swapped one out to one of these and added the sealant.  

 

So there you go.  More than you ever wanted to know about caliper bleed screws on a Miata...


  • Steve Scheifler, 915RACEFACTORY and lillyweld like this
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