I may have cross threaded one of my lines into my new booster/master cylinder😩 any advice?

[scottaskinosie]

I just got my new master cylinder assembly for my 01 cruiser (thanks again for the assist @2001LC!) and 3 of the 4 lines went in easy with my fingers. The fourth started okay but wasn’t as easy. I gave it a tiny tap with my wrench and it moved easily so I thought maybe it had a little debris and kept going. When I got deeper I could tell it was starting to show an angle so I backed it and sure enough, I saw metal debris

I have done this before a couple years ago with a remanufactured part. This same line was tougher going in but never leaked. I’m thinking the remanufactured part may have skewed my flare nut.

Thinking about cross threading these has literally kept me up at night while I waited for the part, and now here I am.

I’ve done some re-threading before but I’m not the most experienced and there isn’t a lot of room in there.

If anyone Knows any tips or tricks or if maybe it might be okay going the rest of the way in please let me know! I’m so close to finally having my car back I don’t want to ruin it now

 

[2001LC]

New master

 

[scottaskinosie]

New master

I’m afraid even then I’ll have the same problem. I believe the remanufactured MC ruined the flare nut…

So new flare nut, reflare the brake line and new MC?

What if it goes in and doesn’t leak?

Thanks LC.

 

[2001LC]

I’m afraid even then I’ll have the same problem. I believe the remanufactured MC ruined the flare nut…

So new flare nut, reflare the brake line and new MC?

What if it goes in and doesn’t leak?

Thanks LC.

If this a reman, just replace. But if new OEM brake master. Worth trying all you can.


There are alternative:

The flare nuts are steel. The captures threads in master, are aluminium. Typically steel isn't damaged by aluminum. But you have to make that call, by inspec each.

You can try cleaning up threads with a threads chase. Try chase (by hand only) on good flare nut, for fitment. If only damaged first few threads in master. Then you've a chance it will hold torque, once master threads chased. But it sound like you ran all the way in, likely damaging to many threads. Which you can not run a chase in all the way, do to male flare tip (cone) within.

If threads of flare nut are damaged. Replace that brake line pipe. It may also be possible, to replace just that flare nut. But make sure to use a metric flaring kit.

I have never done a flare capture thread repair. But it is possible. Google it. You'll see a flare insert.
For the ~$1,500 cost of a master. It worth a shot to try and repair.

If in the end, it leaks. Yes, I'd replace the master.

Tip when installing flare nut:

Pull back the flare nut on pipe, clean and oil pipe. Make sure flare nut, spins freely on pipe. Clean threads of flare nut, and place a small drop of oil on threads. Do not use a wrench, until ready to torque down once all the way on. Torque to 10ft-lbf -+1ft-lbf. Clean with brake fluid cleaner, wipe and make sure dry. Check for leaks after bleeding system, just after key on and active hard braking.

A bit off topic:

I just had to replace and oil pump. Because last guy in doing the timing belt service, used a wrench to drive T-belt tensioner bolt in.
Cross threaded bolts, are tight and hold, until removed. This timing belt had wear marks, indicating pulley misaligned. You want to talk about PITA job. 16 hours extra labor.

 

[scottaskinosie]

Thanks as always man! I did not go that far in, I was WAY too nervous. I did clean it up really good with a brush before starting, but still it wasn't wanting to go in.

I am going to start doing some research on what you have listed above. I REALLY appreciate the advice!!!

I will let you know how it goes.

When this is all said and done, I am going to owe you multiple six packs

 

[badlander]

If you do use a tap to chase the threads, grind out a relief in the end of the tap with a dremel and small round stone or diamond tip for clearance of the internal flare cone in the bore. This will gain you a little more tap depth.

 

[scottaskinosie]

If you do use a tap to chase the threads, grind out a relief in the end of the tap with a dremel and small round stone or diamond tip for clearance of the internal flare cone in the bore. This will gain you a little more tap depth.

Thank you @badlander! Makes sense. I was looking and they’re wondering how to handle that

 

[hoser]

Or blunt tip thread chase.

 

[scottaskinosie]

Or blunt tip thread chase.

View attachment 3831648

Noice! Thanks @hoser!!!

 

[2001LC]

Or blunt tip thread chase.

View attachment 3831648

I've never been sure, if JIS thread different than say m12x1.00, M10x1.50, etc? Is there, a JIS version chase?
.

 

[Malleus]

Same same

 

[scottaskinosie]

Hey everyone, sorry for the delay in getting back with you all on this. I have an update!

I bought a bunch of taps and I was getting ready to try to fix this issue myself and then chickened out and brought it to a shop that has been recommended to me here in Austin.

They had a look and decided they were gonna go for it and it went in no problem

In the end, they got it all hooked up and didn’t even charge me for it. So, all is well that ends well I guess

 

[2001LC]

So you were mistaken and threads actually okay?

 

[scottaskinosie]

So you were mistaken and threads actually okay?

Yep! The threads were fine and I was freaking out over nothing

For whatever reason that one fitting is just a little tighter than the other three...

 

[baltistyle]

I don’t have nearly the experience as others here, but when I replaced my brake lines on an older truck, I had the same issue with one flare nut being tight and it can be worrisome when cranking down on the line to make it seat/seal. Pro tip is to always make sure to use flare wrenches on lines.

Glad it worked out for you.

 

[modus]

In the end, they got it all hooked up and didn’t even charge me for it. So, all is well that ends well I guess

Make sure you give them a 5 star google review and share it others can do the same.
Matters so much to small businesses .

 

[hoser]

Yep! The threads were fine and I was freaking out over nothing

For whatever reason that one fitting is just a little tighter than the other three...

Well, the brake hardline is rarely exactly in-line with the MC, Caliper or whatever. With some 'jiggling' and tightening at the same time, you'll know if it is meant to be.