C1 (1960) Master Cylinder and other brake line leak

[Donald H.]

I recently installed my master cylinder (rebuild/resleeved) and the main brake line from the master cylinder to the first block. Went through bleeding the brakes and I have two leaks that I have not been able to stop.

First - The front of the master cylinder (see picture). The whole front assembly, i.e. the large hex outlet nut, the block and special bolt and washers are new. It is leaking from one or both of the copper washers. I can't tell for sure which one. I don't think I can tighten it any more.

I have order more copper washers. The large hex outlet that screws into the master cylinder has concentric rings where the copper washer fits to it. Also the brass line block has concentric rings on both sides to fit against the copper washers. I assume that the way to get a leak proof seal is to tighten the special bolts to a point where the copper washers are slightly mashed into the concentric ring patterns to form a leak proof seal.

Does anyone have a fool proof technique to installing when I get the new washers I have ordered?

Second - I have a leak in the line from the master cylinder at the first block (second picture). I have bundy tin lines, not stainless. When I installed the line, I tightened, then loosened and re-tightened three or four time. I read somewhere that this technique would help seat the fitting. I have loosened and re-tightened more times now that I found the leak, but still have a leak. The fitting is not cross-threaded as I installed it with fingers before using a line wrench to tighten.

I'm going to completely remove the line and start over, but any other suggestions on how to prevent a repeat of the leak? As far as the line fitting/connections, this is the only place I have a leak!

Thanks,
Don

Master Cylinder leak 2.jpg

Brake line to block leak 2.jpg

[Joe M.]

Re: C1 (1960) Master Cylinder and other brake line leak

Is the first block a repro? If it is original, the repro brake line may be made slightly smaller than required to make a good seal on an original block. You may have to put the brake line that you removed back on to see if that is the problem.

[Richard M.]

Re: C1 (1960) Master Cylinder and other brake line leak

Don,

I had the exact same leaks as you with Dot5 on this '59 I have here. Silicone is less merciful.

I had a new block on the MC and new copper washers. I was able to tighten that one a bit more to correct it. However, I used the original block(1st block) and had a slight leak there same as you. The loosen/tighten trick worked on that one. You may need a new block if the brass bevel inside was deformed. If you do, you may want to reform the brake line end it mates with, using a flaring tool. This will reshape the tubing flare if it got slightly egg shaped.

Rich

[Donald H.]

Re: C1 (1960) Master Cylinder and other brake line leak

Everything on mine is new. My car was a semi basket case and not driveable when I bought it. When I took it apart something like brown/rusty mud came out of the brake lines. I replaced everything with a Corvette Central kit.

I'll look closely at the block.

[Edward J.]

Re: C1 (1960) Master Cylinder and other brake line leak

Don, make sure the copper washers you are using are the correct dia. sometimes if they are slightly bigger sealing problems will arise. don't be afraid to crank the fitting tighter as sometimes this is what you'll need to do. And as Richard says the loosen and tighten again does help especailly with new steel lines. I do this stuff for a living and brakes are generally a part of my everyday routine.