You should never have to use a sealer on a brake line it only promotes future leaks. I would suggest you lube it with brake fluid as you do not want to contaminate the system. When you get to that point, go in a half turn and then out, just as if you were running a tap.once you get it running in and out take it apart and clean the threads.

 

After more frustrating tinkering going nowhere, I finally decided to just torque it down and see what would happen. As you might expect, bad things happened. It spurted out brake fluid when I hit the brake.

After a little more loosening and retightening, I finally got it down in there pretty damn tight, and it seems to be holding for the moment. I suspect it might not hold after I bleed the brakes.

I'm seriously considering just getting a used unit at this point. What a nightmare.

 

You did what? ಠ_ಠ

Start here.

Good luck with your search, and your eventual Option A or Option B fix. And please don't drive the truck until you replace that modulator, lest that fitting blow loose and you become a 5000 pound missile with no brakes.

 

You're absolutely right. I'm replacing the modulator, as I think it's really the only safe way to go. I'm going to grab one from a local scrapyard and put in the new shuttle valve and seals I have, along with the Option B fix I've already wired up. We'll see.

 

Batard, from experience I tend to fit the brake pipes in loosely before bolting the the modulator rubber mounts as it gives you some movement in the modulator wilst locating the brake pipes. Fit the brake pipes loosely to 90% and then bolt up the modulator onto the rubber mounts solidly then tighten up the brake pipes starting from the middle ones first working outwards. When tightening the brake pipe nuts ensure you don't twist the brake pipes, easy done.

The problem being is the modulator bolt holes are large in the bodywork where the rubber mounts go and they rarely return to the exact same position. Good luck, it's a PITA.

 

Yeah, I had the modulator unbolted when first fitting the lines – I tried moving the line around at all angles, but for whatever reason it wanted to thread in two turns in cross-threaded and wouldn't go in any other way. I think there must have been some damage to the threads that I couldn't see.

The damage is done now, though, and I'm getting a new modulator.

 

Is there any sign of damage to the threads on the brake line fitting?

 

It has looked fine every time I undid it and inspected. My feeling is that the steel of the brake line fitting is gouging out the aluminum of the modulator block.

To do a completely thorough job on this, of course, I should replace the brake line/fitting. What are the options there? I've never worked with flare tools, though I've seen them used, and I'm not sure how you'd go about splicing on a new brake fitting or if that'd be better/easier than replacing the whole line.

 

If your close inspection finds no damage to the fitting I'd proceed with it, with careful monitoring of the outcome of course.

 

Brief update: I've decided to order a new brake line (actually the cluster of three that go to the rear wheels and the LF wheel) for peace of mind. I know it'll be a pain to install in that weird bracket on the inner wheel well, but I think the $100 outlay is worth it. I realize I could make my own for less, but I'm too lazy. My only uncertainty at this point is whether the new modulator I'm getting actually works—fingers crossed on that one.