I'm at a loss of what to do as I've never had this happen before. I am installing a V6 master cylinder and brake booster in my 22RE 4runner. I bench bled the MC fine and it bolted up fine, but when attaching the brake lines, the problem began. I had a helper pump the pedal and hold it down before I tightened down the lines, but while one line tightened up fine, one was almost tight enough when it suddenly went soft. Now it won't screw in or out .

My only thoughts are that the line that's broken is an original to the truck, while the working line came with the V6 parts. Also, when my assistent was pumping up the pedal, the first pump was...vigorous. Instead of dripping, brake fluid sprayed everywhere. I told her to take it slower next time, but is there enough pressure in the system to wreck the threads if forced out that hard?

Any help is greatly appreciated, I'm feeling a bit panic'd!

 

Where is the nut turning? At the master or where?

 

Yeah, at the MC.

 

So it just turns or it is stuck?

 

it just turns and turns and turns....

 

Sounds like you stripped the threads in the MC (its only alum). I would pull on the line while I unscrew and try and yank it out. After that you have 2 options. New MC or rethread to a different thread, maybe a standard thread instead of metric. You will have to get a standard nut and re-flare the tube.

 

*sigh*

I'd be better off just taking advantage of the lifetime warranty on the MC than putting strange threads in my truck.

Just out of curiosity, could the high pressure release of brake fluid have messed up the threads? And I suppose there's no way to rethread them back to spec, huh?

 

The short answer is NO. No matter how much pressure you applied you could not damage the thread. The fittings are one of the strongest parts of the system. The internals of the MC would blow apart long before you would burst a line or damage a threaded fitting. You could never produce enough pressure using just the pedal and brake booster to damage any of these parts anyway.

I would guess that the thread in the MC was bad from the start. Return it for a new one.

 

OK, I tried yanking on the brake line while trying to unscrew it, but no dice. Right now, the nut is spinning pretty freely in the MC (I definitely don't need a wrench to turn it), but is no closer to coming out. Thoughts? Where do I go from here?

 

Since you're going to replace the MC, cut the offending brake line and replace it with when you put the new MC in.

 

The brake line is the one that runs all the way to the passenger side frame, so it would be a pill to replace, and I don't have the tools to cut the line properly or to reflare it afterward.