I understand brake fluid is hygroscopic, but I have never personally witnessed internal corrosion in metal lines in the over 100 vehicles I've owned in my 55 years of driving.

Generally brake systems are sealed top to bottom, but I know some moisture laden air CAN get in through the piston seals at the calipers (causing seizing from physical corrosion), and possibly at the filler cap, though most MCs are 100% sealed up there by a bellows type seal. And yes, DOT 5 is a PITA because the system needs to be completely flushed before use.

Not saying it doesn't happen, only that it hasn't happened to me.

 

I had a ton of issues with my 05 Dakota since I bought it a few years ago. I have been through 3 sets of seized calipers. PowerStop calipers was what I was replacing them with and then I purchased new ACDelco calipers off RockAuto and they have been great. Another comment about the brake fluid is I also noticed when going through my brake system with a fine tooth comb, that the master cylinder cap had a ever so slight tear in the rubber that sits inside the cap. So I replaced everything, new cap, full brake fluid flush, new front flex brake lines, new calipers, rotors, rear cylinders, drums, internal drum springs and adjuster. Since I have done that the braking has been great. I think my fluid over time had moisture in it causing the PowerStop calipers to seize. I will say after comparing the two, the ACDelco calipers are far superior in quality.

 

I don't really know how many cars I've owned over the years. Just counting ones bought to drive and not parts cars, somewhere around 250-300. I tried to make a list once but kept forgetting some. I've seen just about every problem over the years that brakes can have. I really like the 1965 and later drum brakes as they are a whole lot easier to work on. The last few years though, instead of brake lines rusting from the inside out, I see them rust from the outside in. Especially in Northern climes. The beet juice added to brine now works great to melt ice. However, unlike salt, it's sticky and a quick rinse won't take it off. It just sits there and eats away at the lines. My neighbor bought a car from the Upper Peninsula in Michigan. 3 years old and he thought he got a great deal. So far I've replaced all the chassis mounted brake lines and the body is starting to show rot. The original owner never washed it.

 

Just finished replacing both front flex lines, and re-bled the system with 1 full quart of new fluid to ensure no contamination, plus I pulled both newly remanufactured calipers and retracted the pistons on the calipers and they went in very smoothly indicating no problem. Inspected the brand new pads and they slide fine, as do the calipers on their brackets (new brackets with nicely lubed slide-bolts came w/ the calipers).

Took the truck for a test drive, using the brakes moderately hard, then driving 5mi to cool them, and upon returning home w/ no brake usage, they are 185 at the hat part of the rotor and 145 at the caliper casting itself. These are overly warm considering the no-brake drive-back.

Other than an ABS or MC problem, I am at a loss. I do NOT think the brake lines are rusted.

Still perplexed!

Bob

 

This makes it sound like a MC port is blocked.

 

Yes, but if the MS port was stopping the fluid from returning to the fluid reservoir, I would have expected trapped fluid under pressure from the calipers (which was likely causing the calipers to drag) to exit the connection at the MC when the flare nut was cracked open, relieving the trapped pressure and allowing the caliper pistons to ease off.

But this didn't happen.

 

Not sure if this 2008 is the same as my 2005, but I only have rear ABS.

 

Good point-

I did not see an ABS unit under the hood, and I didn't notice (but I wasn't looking for) ABS sensor lines coming from the front hubs.

That said, I see listings in the parts catalog for 2008 Dakota 4X4 for front ABS sensors, so some must ave them. I still have the truck in my yard, so I could pull a wheel and check.

I've been using the truck at the owner's request to make it right, and have been using an infrared pyrometer to check brake temps, and the last 2 days I have not seen badly dragging brakes, or crazy hot brakes. Mostly seeing 110-175 deg temps measured pointing the gun at the rotor hats (the portion between the disk surface and the wheels).

The right one is consistently 10-20deg warmer than the left, but the truck is rolling freer, and not boiling hot temps, or smoking.

Maybe the calipers are settling down a bit? I can keep the truck until the week-end and will drive it more, plus the calipers are "Lifetime" units from Autozone so I guess there is some protection. I don't want to throw more parts at it until I collect more data. I think it's hopeful that the highest temps are considerable cooler than 20 miles ago.

The brakes are "good" in that there is no "pulling" with brake application, and it's rolling much freer in neutral.

 

There will be a sensor on the left front even if there is only rear ABS. If they don't know how fast the front wheels are turning, the computer can't figure out how fast the rear wheels should be turning.

 

Took a quick look at the lines, the rear line off my MC goes to a splitter block by the left tire where it splits to the front wheels.

I did my hubs a couple years ago, I don't remember any speed sensors on them.