Before someone asks why I don't just buy new calipers... this is for my LeBaron brake setup with upside-down calipers (GM Metric); banjos up top and bleeders at the bottom. They are cast iron, not aluminium.
The only issue is that these banjos only seem to be available in 1.0 mm and 1.25 mm thread pitches, rather the 1.5 mm GM banjo pitch. I've scoured the internet for the M10x1.5 mm banjo+bleeder combos without luck.
Standard Heli-coils and related are Not made for this job. Brake fluid pressure can easily reach 1200+ psi (80+ bar) and flow thru the coil. More so w/ booster "upgrades" or even just panic stop w/ OE booster.
OEM hose ends and crush washers might barely cover the top and seal for a while. That while might be hours to years.
If you have crap SS hose w/ universal ends, the end often do not crush the whole washer and likely leak like hell when you push the pedal.
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Do you know of any inserts that are better suited for this kind of work? Perhaps one with the crush washer surface included?
Do you think the brake fluid causes erosion as it flows through the coil? If what you're saying is true, then brake fluid also flows in the threads of a stock banjo bolt setup?
[This message has been edited by pmbrunelle (edited 02-19-2020).]
Crush washers seal by crushing over a wide area in a normal banjo bolt setup to seal pressure pushing 1500 psi and more.
But Heli-coil adds a second thread on outside of them plus they are a coil that can flow fluid in it. The Washers must Bridge and seal this very big area and may fail @ high pressure for a panic stop etc.
SS Uni ends often only crushes them in the center w/ the rest of washer doing nothing. If they seem to seal w/ Heli-coil... Don't trust them.
I know of No thread seal available to public or even automotive OEMs that works w/ brake fluid. Now You might see sealer on quick bleed bleeders but in only to keep air out when bleeding. Does nothing to seal brake fluid in. The bleeder tip does that job w/o anything else.
Any leak of brake fluid is trouble even when the pedal doesn't hit the floor... Is likely to be worse because can weep for weeks to months eating whatever drips on etc. Including eating alloy/aluminum wheels. Brake fluid F'ups the finish then the aluminum by interfering normal AlOx layer keeping water salt etc off the aluminum. Most people have no clue how reactive aluminum really is because of AlOx layer instant protect the parts. Likely heard of Flash power and Thermite? Both are Aluminum and an oxidizer.
I don't have a part that's listed for this job. Might call Calipers Online to have these fixed or make others to work. Never used them and some don't like them but been used by many here. Or better, might make ones that works but w/ bleeder at top so can bleed normally. Banjo itself doesn't care where they are and Many caliper shells are make for both sides w/ left/right side made in final machining when they drill the bleeder hole.
Before someone asks why I don't just buy new calipers... this is for my LeBaron brake setup with upside-down calipers (GM Metric); banjos up top and bleeders at the bottom. They are cast iron, not aluminium.
The only issue is that these banjos only seem to be available in 1.0 mm and 1.25 mm thread pitches, rather the 1.5 mm GM banjo pitch. I've scoured the internet for the M10x1.5 mm banjo+bleeder combos without luck.
Why can't you buy new calipers?
Check the STI tap vs. the crush washer. If the ID of the crush washer is large enough to fit over the STI tap, there's nothing to be concerned about.
Originally posted by theogre: But Heli-coil adds a second thread on outside of them plus they are a coil that can flow fluid in it. The Washers must Bridge and seal this very big area and may fail @ high pressure for a panic stop etc.
SS Uni ends often only crushes them in the center w/ the rest of washer doing nothing. If they seem to seal w/ Heli-coil... Don't trust them.
Any workable solution will have to involve the crush washer being compressed with force from both sides... just pure compression, not bending. If this is not the case, then the idea won't pass the minimum feasibility requirement for this project to continue forward.
I think with the M10x1.0 helicoil the solution might be workable. From the Heli-coil catalog, the STI tap for M10x1.0 has a maximum major diameter of 11.422. With a minimal (or no) countersink, I'd need to see the caliper (and my Centric-brand hoses) to see how much of the ridged bearing area remains.
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Originally posted by Larryinkc: Time-Sert thread repair might work.
For now I prefer the Heli-coil, since the crush washers can seal like usual, but it's an alternative.
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Originally posted by Will: Check the STI tap vs. the crush washer. If the ID of the crush washer is large enough to fit over the STI tap, there's nothing to be concerned about.
I think I'd actually choose the crush washer with the smallest ID that will slide over the banjo bolt. If the ID is large, then the crush washer could be installed eccentrically, and then some of the bearing area on the caliper would be left uncovered by the washer. Dorman seems to have a selection of crush washers on their online catalog.
I would probably focus instead on this question: is the remaining bearing area on the caliper large enough, and does it overlap sufficiently with the bearing area on the banjo?
Before someone asks why I don't just buy new calipers... this is for my LeBaron brake setup with upside-down calipers (GM Metric); banjos up top and bleeders at the bottom. They are cast iron, not aluminium.
The only issue is that these banjos only seem to be available in 1.0 mm and 1.25 mm thread pitches, rather the 1.5 mm GM banjo pitch. I've scoured the internet for the M10x1.5 mm banjo+bleeder combos without luck.
Helicoils will work just fine. IIRC its a 10mm size. Just be sure to remove the pistons to get out the metal chips when you drill. The copper washer is all the sealing that you need.
Helicoils will work just fine. IIRC its a 10mm size. Just be sure to remove the pistons to get out the metal chips when you drill. The copper washer is all the sealing that you need.
Had a duh moment... was talking about helicoiling the banjo hole so that he could change the thread pitch from 10x1.5 to 10x1.25 or 10x1.0 in order to be able to use the combo banjo bolt & bleeder screw he linked in his first post: https://www.pegasusautoraci...tails.asp?RecID=5036
That's an unusual reason for a helicoil installation, but doable, I guess.
[This message has been edited by Will (edited 02-21-2020).]
Originally posted by Dennis LaGrua: Helicoils will work just fine. IIRC its a 10mm size. Just be sure to remove the pistons to get out the metal chips when you drill. The copper washer is all the sealing that you need.
If at all possible, I'm going to remove the piston without removing its dust boot. The dust boots are a huge pain to remove and replace if I remember right...
Since these calipers are cast iron, I won't need cutting oil for the drilling and tapping; that will eliminate any risk of chemically attacking the dust boot with oil.
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Originally posted by Will:
Had a duh moment... was talking about helicoiling the banjo hole so that he could change the thread pitch from 10x1.5 to 10x1.25 or 10x1.0 in order to be able to use the combo banjo bolt & bleeder screw he linked in his first post: https://www.pegasusautoraci...tails.asp?RecID=5036
That's an unusual reason for a helicoil installation, but doable, I guess.
That happens sometimes... I think I explain things well, but then for someone else who's not in my shoes, it's not crystal clear.
[This message has been edited by pmbrunelle (edited 02-21-2020).]
I opened the jaws of my slide caliper to the major diameter of the M10x1.0 STI tap.
Then, I then placed the jaws on the ridged bearing area of a Fiero caliper for reference: Not an excessive loss of washer bearing area. I also checked my GM Metric calipers, off-camera. The result was similar to that of the Fiero caliper.
Looks like the pic of the caliper above.
I think the idea is workable.
A Heli-coil repair job for the larger pitches (1.25 mm, 1.5 mm) might be less good, as the STI tap increases in major diameter as the pitch increases.
It looks like you will lose 1-2 'rings' in the crush area. That will leave how many? Maybe you should inspect the remaining ones with some magnification to confirm that they are all good and not damaged from a PO.
Had a duh moment... was talking about helicoiling the banjo hole so that he could change the thread pitch from 10x1.5 to 10x1.25 or 10x1.0 in order to be able to use the combo banjo bolt & bleeder screw he linked in his first post: https://www.pegasusautoraci...tails.asp?RecID=5036
That's an unusual reason for a helicoil installation, but doable, I guess.
Basically agree but if I understand the correct strength of Helicoils, they are stronger than the original threads, so the high pressure argument made by you know who doesn't hold. Stripping out the caliper banjo mounting holes on 30 yr old calipers doesn't take much more than to exceed the torque spec by just a few pounds. You can't keep rebuilding these calipers forever so either welding and re-threading and or using threadserts or Helicoils may be the solution.
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Basically agree but if I understand the correct strength of Helicoils, they are stronger than the original threads, so the high pressure argument made by you know who doesn't hold. Stripping out the caliper banjo mounting holes on 30 yr old calipers doesn't take much more than to exceed the torque spec by just a few pounds. You can't keep rebuilding these calipers forever so either welding and re-threading and or using threadserts or Helicoils may be the solution.
Whether helicoils are stronger or not depends on a lot of factors like the length of the thread, the parent material, how tightly toleranced the installation is, how many load/unload cycles they see...
