Heating up and dragging Front Brakes

Hey, .. I gots a '93 Dynasty! Also a '92 and an '89.

First you need to tell me if one or both front wheels are getting hot. Next, do you have anti-lock brakes? Finally, has anything been done recently to the master cylinder, including adding brake fluid?

Also, when this happens, is the brake pedal higher and harder than normal when you push it?

The hair on the back of my neck just stood up! Where did you attack it with WD-40? There is absolutely nothing in any braking system that is going to be fixed with that.

A faster way to tell if the car has anti-lock brakes is to look at the master cylinder. If you have standard brakes, the master cylinder will be about 8" long, a bluish-colored anodized aluminum, with a black plastic, ... Wait a minute. Pictures are faster.

These are from Rock Auto which I use a lot for reference. They aren't to the same scale. You most likely have the master cylinder on the left. It's shown looking at it from over the left front tire / fender. If you have anti-lock brakes, you'll have the Bendix-10 system which uses the unit on the right. This one is shown looking down on the top of it. This one is more than twice the size of the one on the left.

My concern is when both front wheels are getting hot. There's a real simple fix when only one wheel is affected, and we may still find that to be true for each wheel individually, but for now, find a "flare-nut" wrench, also called a "line wrench", that fits the soft metal nuts on the lines attached where my nifty red and blue arrows are pointing. I can't remember the size, but it should be around a 3/8" / 8mm. A standard wrench may work, but it's real easy to round off the nuts because they are very soft.

When the problem is occurring, stop on a slight incline, shift to neutral, and assuming the car doesn't creep downhill on its own, place a block about a foot downhill from a tire so you don't look funny chasing after the car if the brakes release! Use the flare-nut wrench to loosen those two steel line nuts about a half turn each. If the brakes release, we'll have to discuss this further because this is going to be a very expensive repair. The brake fluid was contaminated with a petroleum product like engine oil, transmission fluid, power steering fluid, axle grease, or, ... WD-40!

If the brakes do not release, breathe a sigh of relief. I'll describe where to go next once you verify the car doesn't have anti-lock brakes. You didn't answer my question about the brake pedal. Is it higher and harder than normal?

The recall was for the master cylinder on ABS-equipped cars. I got the part for mine when I worked at the dealership. Can't find it now, but it doesn't matter. My car doesn't even have 5,000 miles on it yet!

In addition to loosening the lines at the master cylinder, inspect the rubber bladder seals under the two reservoir caps. They will pull down over time due to brake fluid leaving the reservoir as the front brake pads wear down. You should be able to pop those seals back into the caps real easily. The serious clue you do not want to see is when those rubber seals are blown up and mushy. If you can't get those seals to pop into place and stay there, we'll have to talk about the next step. Be sure your fingers are clean when you touch those rubber parts.

If those seals are okay, chances are you do not have the serious condition I was worried about. That is brake fluid that got contaminated with a petroleum product such as engine oil, transmission fluid, power steering fluid, axle grease, or penetrating oil. As little as one drop, or a light film on your fingers is enough to contaminate the entire hydraulic system. The only acceptable repair for that is to remove all parts that contain rubber, including seals and o-rings, flush and dry the steel lines, then install all new rubber parts. That includes calipers, wheel cylinders, rubber flex hoses, master cylinder, and combination valve. If any rubber part is not replaced, the contamination will leach out of it and recontaminate the entire system again.

It's looking like you're going to have a more common problem with a REAL involved solution. Turn the steering system fully one way, then crawl underneath on the side where you can see the rubber brake hose. Look for the metal bracket that my nifty red arrow is pointing to in the photo. Use a large flat-blade screwdriver or a large pliers to open up that bracket where it is crimped around the hose. Rust builds up inside that crimp and constricts the hose. Brake fluid pushes real hard through that restriction. That's why the brake pedal is higher and harder than normal. The fluid can't return easily, so it keeps that caliper applied. As the brakes get hot, that heat migrates to the brake fluid and makes it expand. That self-applies that brake even harder.

If that doesn't solve the problem, turn the steering system the other way and do the same thing on the other front hose.

Years ago when repacking front wheel bearings was a common part of a front brake job, a person's hands would be all full of grease. If you wipe your hands off real well on a clean rag, then check the fluid level in the master cylinder, you'll find those rubber seals under the cap pulled down. We pop them back into the cap with a cleaned fingertip, and presto, you've just contaminated the system with the residue on your fingers.

Often the soft metal nuts that connect a rubber flex hose to a steel brake line become rusted tight, especially if you live where I do where they throw a pound of salt on an ounce of snow. Some mechanics think they can break the nuts free so they'll spin on the line by spraying them with penetrating oil. Heat from a torch works better, but then some people apply grease to the line to prevent it from rusting again. It's a good bet some of that grease will find its way into the fluid.

Many years ago I bought an old Edsel at an auction. Within a few days it took a tank of gas to drive less than 75 miles. While driving on a granite driveway, the right front tire was skidding. Come to find out, the previous owner had drained the master cylinder and refilled it with transmission fluid! That will make the rubber seals swell and seal better, ... Just long enough to sell the car to some sucker. I had to rebuild the master cylinder, all four wheel cylinders, and replace the flex hoses.

I worked for the Auto Center at a mass merchandiser in the '80s, and we used a "bleeder ball" to pressurize the hydraulic system to make bleeding go faster. Those bleeder balls hold three to four gallons of brake fluid. We filled them from five-gallon pails with a funnel. Through our training center we heard of a guy at a store many states away who grabbed a funnel used for engine oil, wiped it clean with a rag, then used it to fill the bleeder ball. The residue from the oil found its way into at least a dozen cars. The store had to pay for hundreds of dollars worth of parts for each car, plus a real lot of labor time.

The important point is the contamination flows throughout the entire system and sinks into the rubber parts. If any rubber part is not replaced, the contamination will leach out of it and re-contaminate the system again. The only time is acceptable to not replace everything is when you see someone in the process of doing something to contaminate the fluid. If you get the master cylinder off the car right away, you may be able to save the other parts down the line. If you wait a few hours, it's too late.

Every year I did a demonstration for my students, and you can do the same thing if you get some reservoir cap seals from a salvage yard. I had two beakers filled with an inch of fresh, clean brake fluid. I dropped one wheel cylinder lip seal into each one. In one of them I added one drop of power steering fluid, mixed it up, then set them both on a shelf. One week later I washed them off, then passed them around for examination. The one with power steering fluid had grown from about 7/8" to over an inch, and it felt mushy or gooey. If that happens in a master cylinder, the seals grow past the fluid return ports and blocks them. Normally, when everything is working properly, there is a clear path for heated and / or expanding brake fluid to release and flow through the return ports and up into the reservoir. When you push the brake pedal, it takes the first inch or two to move the lip seals far enough to pass the return ports and block them. At that point all the fluid ahead of the seals is trapped and has no choice but to get pushed down to the wheels as you push further on the brake pedal. The point is those return ports become unblocked by the time the pedal still has a couple of inches to release. When the seals have grown larger from the contamination, they keep those return ports blocked all the time. That is what keeps the brakes applied, then the dragging brake gets hot, and that heat migrates through the caliper and into the fluid. Hot brake fluid expands, and since it is blocked from flowing back into the reservoir, it puts more pressure in the caliper, and that brake applies even harder.

The issue, I should explain, is brake fluid is not a petroleum-based product. It has to remain very thin and fluid down to very low temperatures. As such, it is a glycol product and all rubber parts have to be tolerant of glycol. Those parts are not compatible with petroleum-based products.

In the '80s it was also common practice to rebuild wheel cylinders and calipers as part of a brake job. Most of us would wash our hands with soap and water before installing the new rubber seals to prevent getting fingerprint grease on them. We also had to watch for leaking rear axle seals. That gear lube usually contaminated the brake shoes first, resulting in the visit to our shop, but once the seals were replaced, we still had the opportunity to get that gear lube residue on our fingers, and inside a wheel cylinder we were rebuilding.

Hold on. Are you saying someone is going to replace the master cylinder? That is not the solution. You need to open up those brackets where they're crimped around the rubber flex hoses. If the master cylinder was causing this problem, it would be due to fluid contamination, and loosening the two steel lines attached to it would let the brakes release.

I never looked at either of my Dynastys, but I suspect those brackets can be stretched open without removing the wheels. I had to do this to two of my four Grand Caravans, and the hardest one took the better part of three minutes, and two of those were to find the tools.

Rust builds up inside the bracket between it and the hose. That is like making a fist around the hose, then squeezing it closed. Opening the bracket is like relaxing the fist.