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2G 3kgt Brake Swap Fitting Leak

Kai Hefner

Freelancer
458
217
Jun 21, 2018
Calgary, AB_Canada
I haven’t put many km on my car since I did a 3000gt front brake swap. I used the volk metal craft kit which worked well, and got brand new calipers. I also bought the inner-wheel brake line from a vendor that came recommended on the forums for this swap. The line was fine for around 1000km, but when I was pushing the car today, I lost brake pressure. Upon inspection, the fitting connecting to the caliper is leaking. I installed the line properly and tight, and only stripped it today when I was trying to tighten it even more to see if it would fix the leak. Even with a bit more tightening, it still leaks!

If I understand correctly, the line fitting and the caliper have matching flares to keep them from leaking. Has anyone encountered this issue and found a solution? I sort-of destructively tried fixing this line, would anyone have reccomendations for a new line? This current one was insanely soft, hopefully something harder?

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scotthidley

Proven Member
152
11
Nov 7, 2004
Cleveland, Ohio
If your lucky, you stripped the fitting on the line. I stripped the fitting on the caliper as the caliper is aluminum and the line cross threaded quite easily. Make sure the flares compliment each other. I got reman calipers for the vented rear swap and the flare was actually machined the wrong way in the caliper. It's possible you had something similar on the front. Either way, if you stripped the caliper or if it's wrong, you can order a new caliper and switch that half if you have Mitsu logo cast in the outer face, or you can order replacement lines (even with a flare in the other direction). Techna-fit made custom lines for me, it didn't take long and wasn't much more than standard lines.
 

Kai Hefner

Freelancer
458
217
Jun 21, 2018
Calgary, AB_Canada
If your lucky, you stripped the fitting on the line. I stripped the fitting on the caliper as the caliper is aluminum and the line cross threaded quite easily. Make sure the flares compliment each other. I got reman calipers for the vented rear swap and the flare was actually machined the wrong way in the caliper. It's possible you had something similar on the front. Either way, if you stripped the caliper or if it's wrong, you can order a new caliper and switch that half if you have Mitsu logo cast in the outer face, or you can order replacement lines (even with a flare in the other direction). Techna-fit made custom lines for me, it didn't take long and wasn't much more than standard lines.
Just stripped the 14mm fitting on the line. I've already been down the caliper-stripping path before. How are those Techna-fit lines? My concern is really this fitting. It's a 14mm, but a 14mmm wrench had a lot of play on the fitting. Paired with the soft material, I was surprised I didn't strip it before I had this issue. I want something harder, and able to withstand more brake pressure. My guess is that whatever seal on the fitting gave out with really brake high pressure. The other side was installed exactly the same and doesn't have any issues but I'm holding my breath.
 

steve

DSM Wiseman
13,795
879
Feb 3, 2002
Boulder, Colorado
I don't remember my brake lines on by RT/TT bottoming out in the caliper. They seat with a mm or two gap between the nut and the caliper body. You sure it was the correct fitting on the line? That looks more like it wanted a copper crush washer between the two.
 

Kai Hefner

Freelancer
458
217
Jun 21, 2018
Calgary, AB_Canada
I don't remember my brake lines on by RT/TT bottoming out in the caliper. They seat with a mm or two gap between the nut and the caliper body. You sure it was the correct fitting on the line? That looks more like it wanted a copper crush washer between the two.
I ordered the lines from some vendor that was reccomended on the forums for the swap. Maybe they just weren’t right? I couldn’t even explain the height thing. Lines didn’t come with any crush washers either, I’m pretty sure in the past it prompted me to ask someone and I was told that the flares between the caliper and line fitting create the seal. Could someone confirm this?
 

Kryndon

Proven Member
675
357
Jan 10, 2014
Bulgaria, Europe
Yes, the flared ends between both objects create the seal. There are two main types; banjo bolts + crush washers as they come originally on our 2Gs, or flared fittings such as on the 3000GT.

For the banjo bolt, it's the copper crush washer that provides the seal. For the other type, it's the flared ends that need to match up smoothly to allow for a proper seal. Some inverted flare fittings may differ, however. Or they might be poorly machined.

When I did this swap, I took the calipers (and the cut off original brake line) to a hydraulic shop and told them to make me new lines with this exact flared fitting. Both lines cost no more than $20 and they still haven't leaked or collapsed. Here's a picture so you can see that on mine, the fitting also sticks out but it's properly bottomed out. No need to shorten it or add crush washers.

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Kai Hefner

Freelancer
458
217
Jun 21, 2018
Calgary, AB_Canada
This is what I'm thinking about doing. I'll be bringing the line to a local shop today and see if they can copy it. I'm guessing my issue lies in this bottoming-out fitting, it probably didn't create the proper seal with the caliper.
 

m1nd64m3

Proven Member
690
8
Sep 17, 2003
chitown area, Illinois
I ran into the same issue with mine although I didn’t strip the threads. I ended up using permatex 54540 hydraulic Sealant on the threads and haven’t had any issues since. I figured I’d give the sealant a shot vs possibly stripping out the threads by over tightening.
 

Kai Hefner

Freelancer
458
217
Jun 21, 2018
Calgary, AB_Canada
I ran into the same issue with mine although I didn’t strip the threads. I ended up using permatex 54540 hydraulic Sealant on the threads and haven’t had any issues since. I figured I’d give the sealant a shot vs possibly stripping out the threads by over tightening.
I'll give that sealant a try! It's fine for brake systems? I was going to use teflon tape but I read somewhere that brake fluid decomposes it. Also, maybe I worded it wrong, but I didn't strip any threads! Just where the wrench goes on the fitting.
 

scotthidley

Proven Member
152
11
Nov 7, 2004
Cleveland, Ohio
Just stripped the 14mm fitting on the line. I've already been down the caliper-stripping path before. How are those Techna-fit lines? My concern is really this fitting. It's a 14mm, but a 14mmm wrench had a lot of play on the fitting. Paired with the soft material, I was surprised I didn't strip it before I had this issue. I want something harder, and able to withstand more brake pressure. My guess is that whatever seal on the fitting gave out with really brake high pressure. The other side was installed exactly the same and doesn't have any issues but I'm holding my breath.
Maybe the fitting was defective, but in general, most hose assemblies are designed to have the hose be the weak point. My fittings were fine. Make sure you're using a flare wrench too. The Techna-fit fittings look to be plated low carbon steel as they're magnetic.
 
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