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Caliper bracket question

I knew I shouldn't have said it's fixed! After driving it for several days with the brake pedal travel being better and acceptable, as we left for my granddaughter's dance recital last night, the brake light came on. Should have, but didn't, switch vehicles.

This morning, I found a leak at the rearmost line on the master cylinder. It was tight, but leaking, so I tightened it some more and set about bleeding the brakes. That was an ordeal in itself. I knew one of the rear bleeders was rounded off and had already bought new ones. Should have read the reviews. The Brake Best bleeders from O'Reilly's are not a direct fit. One reviewer said they don't work on a '02 Sport Trac. They leak no matter how much you tighten them. Took those back and exchanged them for the Dorman bleeders I had used on my '01. Couldn't get those to stop leaking either. The tip is slightly longer, wider, and more pointed than the originals and don't seat properly. I ended up taking the Dorman bleeders out of the front calipers, and FINALLY got one to seal, but I had to really crank it down. I'll be looking for original bleeders at the salvage yard in the future.

After thoroughly bleeding all 4 corners, I went for a test drive and found the pedal feel is right back where I started. Got home and checked the rear bleeders for leaks. They look ok. Went to the left front and saw fresh brake fluid on the ground and dripping from the inner fender. When I got a helper, I quickly found the rear fitting is still leaking profusely when the brakes are applied. For some reason, that line and master cylinder don't seal. That was not what initially caused the long pedal travel though. The pedal felt pretty good after switching master cylinders until I ran it low last night. It didn't feel that bad even until I lost all that fluid trying to get a bleeder to seal in the rear. I'll try the line from the '01 that was originally mated to this master cylinder.

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Oh dang!

Remove the line and check the flare, no burrs or knicks allowed

Bleeders get rounded off nothing sucks worse! Good pair of vise grips can help to get the old one out but I hate to put the rounded ones back on… hahaha have done it a time or two until can get new ones
Maybe this is something I should
Collect from junk trucks… stupid aftermarket parts!

As I was showering this morning and not really thinking about the truck, I realized the fitting isn't leaking. There's a rubber o-ring between the master cylinder and the part the line attaches to (not shown in the factory manual so I don't know what it's called). I had noticed that the o-ring isn't uniformly seated. The o-ring is what's leaking. The leak is on the bottom side where it can't be seen. Fluid was dripping from that part. That makes so much more sense than the fitting leaking. The fitting would have to be badly damaged to leak that much, and fluid would shoot toward the fender, not drip downward. I like the idea of changing the o-ring better than dealing with a bad line and or damaged part. The hard lines came with the ABS unit I swapped 2 years ago and haven't leaked. The m/c came out of the parts truck as is. The o-ring didn't leak on that truck. My point is, this is the current problem, and is related to the fix, not the original problem.

That part I couldn't identify seems to be a check valve to prevent brake fluid from the rear brake lines from flowing back into the master cylinder. There are 2 o-rings, one where the valve screws into the master cylinder and one in a groove on the outside that doesn't look to do anything except cover a tiny hole. Maybe that hole is like the weep hole on a water pump that leaks when the internal seals go bad? Anyway, I think that weep hole is where the leak was. The valve in the end seems looser than one I got from the salvage yard when I got the ABS unit 2 years ago, so I'm thinking this valve is bad. I can't find anything online to match it, but one site selling them for racing vehicles says without a check valve, the brake pedal will have extra travel before engaging the brakes.

I changed the check valve and the pedal feels pretty good, but the leak was at the fitting. I changed the line and it's still seeping a little, but not dripping like yesterday. Pedal feels better than it has in a while.

Is there a sealer I can use on the threads, or am I going to have to live with a slight leak? The only other option I can think of is to go to the salvage yard, take the line loose at the ABS unit, take the master cylinder off so I can unscrew the check valve and line together. Then do the opposite to install the check valve and line on my truck. That would eliminate taking the line loose from the check valve.

Get a new master cyl without that stupid valve ;)
I’ve seen that thing before I always thought it was an adapter to go from
The newer style brake lines into the older style master cyl. The old rear brake line used to be double the size fitting at the master

That “valve”’or “adapter”
Eventually went away, I don’t think a new master cyl would have one anymore and your line should thread right in

No leaks allowed on brake lines

Thank you. That part is for full-size trucks and vans, but it seems to be the only one available. New master cylinders don't come with the valve.

I did find these posts from another site explaining what it is and does. OP on that thread was installing Explorer/Ranger parts on a late 40s truck.

From the '96 Bronco shop manual

Fluid Control Valve, Brake Master Cylinder
The brake master cylinder fluid control valve (2C161) regulates the hydraulic pressure in the rear brake system. It is located on the brake master cylinder (2140) and is screwed into the rearmost outlet port. When the brake pedal (2455) is applied, the full brake fluid pressure passes through the brake master cylinder fluid control valve to the rear brake system until the valve's split point is reached. Above its split point, the brake master cylinder fluid control valve begins to reduce the hydraulic pressure to the rear brakes, creating a balanced braking condition between the front and rear wheels (1007) to minimize rear wheel lockup during hard braking.

In case of the front brake system malfunction, the brake master cylinder fluid control valve has a bypass feature which allows full hydraulic pressure to the rear brake system.

Another post in the same thread
The valve in question is called a screw-in proportioning valve, and in this case with the added "tip" valve feature. Screw in valves became popular because of the need for two prop valves in cross-split hydraulic systems, mainly on front drive vehicles, but also found on vertical split systems as the one the O.P. is using. This master cylinder has the primary portion going to the drum rears. In the event of a secondary front axle brake failure, the primary piston will move farther than normal and "tip" the small extension protruding out the prop valve, bypassing any proportioning and allowing full M/C pressure to the rears.
Here' the link to the full thread

I drove my truck about 15 miles last evening and the pedal feels really good. It does have seepage past the threads, but not like it was Saturday with the other valve and line.

The first explanation of what the valve does said that when the rear drums are released, fluid is forced back to the master cylinder. That lessens the pressure in the rear lines. This valve prevents that and keeps some pressure in the rear lines so they engage when the brakes are applied without delay. Everything I've found says these valves are used in front disc/rear drum systems, but my '04 with rear discs also has one.

If it starts to leak try some Teflon tape , NO Leaks on brakes

Your 04 has one too? The mystery deepens!!!

I have a 02, 03, 04 and 05 tracs outside I’m going to investigate this later
Today lol

I drove about 50 miles yesterday - in town, open road, a little bit of freeway, and a little stop and go rush hour traffic - and about 15 miles this morning. No discernible loss of brake fluid and pedal travel is what it should be.

Side note - I briefly considered eliminating ABS entirely this past weekend - nothing to do with the brake pedal travel except I was having trouble getting the brake line attached to the ABS and master cylinder because there's no flexibility in the line. What I think I learned about ABS is that unless the ABS unit is banging and making noises, any problem with ABS is likely with the electronic module that controls the hydraulic unit. I removed the fuse to disable ABS a few years ago because the truck was creeping ahead instead of coming to a complete stop at times in normal driving. I almost crept into the rear of other vehicles and the concrete wall in the parking garage at work. That's the electronic module malfunctioning and thinking ABS needs to be activated when it doesn't. I later changed both the electronic module and the hydraulic unit, which is a major pain as you have to find a way to bleed the hydraulic unit. I think I could have just replaced the electronic module. They're generally sold together as 1 part as the module plugs into the side of the hydraulic unit. I think most people selling them used use the part # for the module as the # for the whole thing, which is confusing because that's not the most visible # when looking at it in the truck.

I deleted mine :)

The abs computer does the “buffering”’for the speedometer signal so if you remove it you just replace it with a Dakota digital speedometer interface (or similar device) so the truck remains happy. The pcm, instrument cluster and cruise control need to see a signal from the vss

I do not like the pedal pumping and system on the 95-04 trucks at all I hate it, so on
My personal rides we delete it