Z32 BMC Fitting Leak - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

derass · 06-20-2015, 08:06 PM

Has anyone experienced a leak where the flare nut connects to the port on the BMC where the fitting is added?

While checking things over at the track, I noticed that the reservoir was low and that there was a slow leak at said connection. This is a newly assembled S13. The brake parts came from my old car which served 5 years of track duty and never had this leak.

I am thinking that the fitting is not seated properly in the BMC and just needs to be reassembled. Just wanted to see if anyone had input before I take it apart. Thanks!

KiLLeR2001 · 06-20-2015, 08:35 PM

Could be a few things, either way you will have to take off that particular brake line and inspect everything.

S14GE · 06-21-2015, 02:51 AM

Make sure the flare on the bmc matches the flare on the line

derass · 07-02-2015, 11:36 PM

Well, I took it apart today and I think I have an idea of what's going on. I reassembled everything 3 times, and it would still leak.

As you can see here, there is some damage to the fitting where it seals against the inside of the BMC. As I said before, this setup did not leak in my old car, so I must have caused this damage by tightening the flare nut with the fitting not seated correctly.

I had a spare BMC from an S13, so I figured that would take a new fitting from that. Turns out it was a reproduction and does not have the fittings, it is all one casting.

I am concerned that there is now damage to the interior of my Z32 BMC because if this happened to the steel fitting I can only imagine what happened to the aluminum casting of the BMC. I will have to remove it from the car to get a good look. It was very hard to see inside that port with it on the car and fluid pouring out of it.

paobender · 07-03-2015, 06:51 AM

yes,It was very hard to see inside that port with it on the car and fluid pouring out of it.

derass · 07-07-2015, 10:45 PM

Well, I managed to fix the leak.

I was able to inspect the inside of the port without removing the master with a clever trick suggested by my brother. With the line in question disconnected, he sat in the car and pressed the brake pedal to the floor, some brake fluid poured out but then stopped (because the piston was fully extended). I then cleaned the port with brake cleaner and was able to inspect with a flashlight and mirror. It wasn't easy to get a good angle and view, but I was able to see that there was no significant damage. There was the possibly of some minor, non-visible damage because if the seat where the fitting rests was not flat even by a few thousandths of an inch there could be a leak. I decided to take the chance.

I bought an OEM master cylinder from an S14 locally. The OEM master had the fitting and I cut it out. I reassembled with the new fitting, making sure to hold the brake line against the fitting in the port while tightening the flare nut by hand. This is where I went wrong last time. I remember that I just barely got a few threads started then used a wrench the rest of the way. The fitting must have been crooked and forcing the nut with the wrench caused the damage. Tightening the nut by hand prevented any damage.

I guess i got lucky because if the new fitting still leaked I would have likely had to replace the Z32 master. Hope this helps someone in the future!

06-20-2015, 08:06 PM	#1
derass Zilvia FREAK! Join Date: Jun 2010 Location: Toronto, ON Age: 36 Posts: 1,182 Trader Rating: (0) Feedback Score: 0 reviews	Z32 BMC Fitting Leak Has anyone experienced a leak where the flare nut connects to the port on the BMC where the fitting is added? While checking things over at the track, I noticed that the reservoir was low and that there was a slow leak at said connection. This is a newly assembled S13. The brake parts came from my old car which served 5 years of track duty and never had this leak. I am thinking that the fitting is not seated properly in the BMC and just needs to be reassembled. Just wanted to see if anyone had input before I take it apart. Thanks!

06-20-2015, 08:35 PM	#2
KiLLeR2001 Post Whore! Join Date: Jun 2007 Location: オーランドフロリダ Posts: 7,955 Trader Rating: (46) Feedback Score: 46 reviews	Could be a few things, either way you will have to take off that particular brake line and inspect everything. __________________

06-21-2015, 02:51 AM	#3
S14GE Zilvia Member Join Date: Jan 2007 Location: Norfolk, VA Age: 36 Posts: 190 Trader Rating: (0) Feedback Score: 0 reviews	Make sure the flare on the bmc matches the flare on the line

07-02-2015, 11:36 PM	#4
derass Zilvia FREAK! Join Date: Jun 2010 Location: Toronto, ON Age: 36 Posts: 1,182 Trader Rating: (0) Feedback Score: 0 reviews	Well, I took it apart today and I think I have an idea of what's going on. I reassembled everything 3 times, and it would still leak. As you can see here, there is some damage to the fitting where it seals against the inside of the BMC. As I said before, this setup did not leak in my old car, so I must have caused this damage by tightening the flare nut with the fitting not seated correctly. I had a spare BMC from an S13, so I figured that would take a new fitting from that. Turns out it was a reproduction and does not have the fittings, it is all one casting. I am concerned that there is now damage to the interior of my Z32 BMC because if this happened to the steel fitting I can only imagine what happened to the aluminum casting of the BMC. I will have to remove it from the car to get a good look. It was very hard to see inside that port with it on the car and fluid pouring out of it.

07-03-2015, 06:51 AM	#5
paobender Join Date: Jul 2015 Location: CA Age: 39 Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	yes,It was very hard to see inside that port with it on the car and fluid pouring out of it.

07-07-2015, 10:45 PM	#6
derass Zilvia FREAK! Join Date: Jun 2010 Location: Toronto, ON Age: 36 Posts: 1,182 Trader Rating: (0) Feedback Score: 0 reviews	Well, I managed to fix the leak. I was able to inspect the inside of the port without removing the master with a clever trick suggested by my brother. With the line in question disconnected, he sat in the car and pressed the brake pedal to the floor, some brake fluid poured out but then stopped (because the piston was fully extended). I then cleaned the port with brake cleaner and was able to inspect with a flashlight and mirror. It wasn't easy to get a good angle and view, but I was able to see that there was no significant damage. There was the possibly of some minor, non-visible damage because if the seat where the fitting rests was not flat even by a few thousandths of an inch there could be a leak. I decided to take the chance. I bought an OEM master cylinder from an S14 locally. The OEM master had the fitting and I cut it out. I reassembled with the new fitting, making sure to hold the brake line against the fitting in the port while tightening the flare nut by hand. This is where I went wrong last time. I remember that I just barely got a few threads started then used a wrench the rest of the way. The fitting must have been crooked and forcing the nut with the wrench caused the damage. Tightening the nut by hand prevented any damage. I guess i got lucky because if the new fitting still leaked I would have likely had to replace the Z32 master. Hope this helps someone in the future!