Hey again,

So it appears one of the brake line ports on a master cylinder I tried to install is cross-threaded. Not sure if it came this way or if it's my fault, but it seemed a bit uncooperative w/trying to hook up lines to it to bench bleed it, and it became quite obvious when it was impossible to get it to screw back in properly and I had brake fluid leaking like mad.

Question is, is it safe to use a tap and die set to rethread the port? Or is this a bad idea with such a crucial brake system component? Please give me some good news, I'm about to give up on this car entirely with the way things are going on it :/

 

Since the ports are so shallow and have a tapered seat at the bottom, I.would not try to fix it, that and you will end up filling the piston with shavings.

New ones are pretty inexpensive. What master are you working with? Does it have the right threads? That may be how it gotmessed up

 

Well, I'm not sure if the master cylinders changed much over the years, but my car is a '91. It was a Cardone select (new, not rebuilt) one I ordered off rockauto. The threading on the damaged port is pretty messed up, so it's hard to even tell at this point if it was the right threading.

Unfortunately, it's only online where I seem to be able to get new units cheaply and easily (most parts shops around me only seem to have rebuilt ones in stock), and I'll be leaving out of town later this week, so looks like this thing will have to sit...some more

Most people I've talked to always say to buy new when it comes to the MC, so I've kind of been skeptical to try rebuilds.

 

So I had a couple more questions. I got my hands on another MC, but ran into a couple of small issues. It seems like no matter how hard I tried and how closely I followed directions, I just couldn't get the master bench bled 100% perfect, but got most of the air out. Is this still better than doing no bench bleeding at all?

Also, I cant seem to get the prop valve line nut (the one closest to the booster) screwed into the MC 100%, as it stops and gets tight around the last thread, but there are no visible signs of damage, and no leaks. I wanted to be extra careful this time, but I dont see it getting all the way down without forcing it. Does the connection just need to be nice and snug without leaking? Or absolutely perfect?

 

I replaced my master cyl and prop valve, and I did a terrible job tryign to bleed it also.

I just ended up trying to gravity bleed it on all four corners and used a few quarts of brake fluid over a couple of hours. I have my doubts about how 100 percent it is, but it feels good when Im driving around. Firm pedal, I just cant rule out there's not a little air inside the master cyl somewhere.

If I had to do it again I'd just dump the whole master cylinder into a bucket of brake fluid and pump it as much as possible, pull it out and plug it and install it after wiping it off.

 

If your talking about getting the threads completely into the MC like a bolt tight to a valve cover or head it does not need to happen and usually does not.
The reason is because the line is flared and the nut is also shaped t the flare, and MC. The flare is pressed by the nut into the MC. That is what seals. So you kinda want extra threads so the flare can be fully seated.
This is also why you never use thread tape on a flared fitting. It serves no purpose at all, and will not fix it.

 

Kcb37: Thanks! Finally, some news I like hearing . I will bleed the system at the wheels and finally give it a good ol test drive when I'm back home from my vacation.

On another, somewhat non-related note, I may have figured out what's been causing my motor to run sluggishly since owning this car. While installing the MC, I noticed a couple of missing intake manifold bolts I never noticed before! Would this cause a vaccuum leak/running rich?