Sticking Caliper

[Omie01]

I took my Mustang out a couple months ago, and felt a pull when I hit the brakes. So yesterday I looked into it, figured I would replace the caliper (on the drivers side, it was hard to turn) and see if that helped. The rotor still spun with a little resistance but I took it for a ride anyway. Needless to say, by the time I was heading home at the last stoplight my front drivers side brake was smoking a bit. So now I know the caliper is staying a little tight. I have a set of Russell stainless braided flex lines up front that I installed about 5 years ago. I am thinking that the line on the drivers side is not allowing the fluid to release tension on the piston. Does this sound plausible? The proportioning valve wouldn't affect just one line would it? Any help would be appreciated.

 

[Fabrice]

It could be a collapsed line, but as they seams to be not that old and from a respectable brand. I would first remove the pads and check them. if corrosion has found its way on each side of them, they no longer move smoothly and do not return to the expected "floating" position. Also, what caused a similar issue on my 73 was to have replaced my pads, from Rockauto and of well known brand (unfortunately I don't recall which one) and they were a bit too tight, so after just a coule of miles, they were expending and were stuck causing the wheels to get hot. The next day, cold, there was zero problem. Fix was to grind them just a tad. Of course some grease on the contact guide helps.
Another bad guy, other than rusted out callipers or collapsed flexible, is if you have changed the master cylinder or booster and did not adjust the little rod it may be too far engaged and keeps a little pressure to the master piston.
I would also if you do not drive the car often or have not for a while, inspect the calliper's piston and press it back to see if it travels smoothy/nicely.
Other than that. if the problem persist, and the pads/rotor have no obvious damage/grooves. I would disconnect the flexible calliper side. which should drip right away and with depressing the pedal you should see a normal flow. On braided lines you can not really see if the line expands under pressure as with regular lines when collapsed. You would certainly feel resistance at the pedal.

If you have the original brakes and do not drive it often and it was fine before, I could bet it's the pads not returning to their relax position due to corrosion/dirt. As usual only inspection will tell.

The proportioning valve would indeed affect both sides and if your electrics are in good shape, the idiot light should stay on on your dash.

EDIT: forgot to say that if you test you line. before disconnecting. jack the car, depress the pedal hard. Go feel the wheel by hand. then disconnect and if the line is collapsed, the calliper should relax and the wheel turn with much less drag.

 

[mjlan]

If its only happening at one front wheel I would think its something on that corner- the hose, the caliper etc.

But your question is valid- I do think the OE prop valve handles the split in the front circuit. Pressure comes into the valve from the master and then out to each front corner. There is a single outlet for the rear which is then split on the axle housing.

Get it hot and sticking then loosen the line or the bleeder on the sticky caliper. That will tell you if the hose is blocking fluid flow.

 

[73pony]

I had same issue last year on front passenger side. the SS hose had collapsed inside.

 

[Omie01]

So I decided I believe the problem to be a collapsed brake line. ( I will confirm by loosening the bleeder) I have a set of StopTech slotted rotors in my car. As i said, when I had it out last the rotor on the drivers side was smoking a little at a stoplight, do you guys think this rotor is still safe to use? I do plan to repack the bearings and such. I ordered a set of rubber flex lines, and a set of Hawk Performance pads. Hopefully this will fix the issue. Thanks for all the input.

 

[Omie01]

Sorry, just have to ask again. If my rotor got hot enough to smoke a bit, is it still safe to use? Should I look for discoloring?

 

[351c1971]

Since the rotor was new, the thickness should be adequate. If the petal does not pulse when the brakes are applied, it is not warped and should be OK to use. You can sometimes (but not always) feel if the rotor is warped when turned by hand.

 

[Cleveland Crush]

Sorry, just have to ask again. If my rotor got hot enough to smoke a bit, is it still safe to use? Should I look for discoloring?

Visually inspect both sides of the rotor in question for cracks not to be confused with normal heat checking. Provide us with good photos of your rotor surface for better feedback. My feeling is the rotor is fine, BUT, have a qualified mechanic inspect it if any doubts!

 

[351c1971]

Also be aware that most rebuilt calipers do not have new pistons. As the chrome plating wears, the piston becomes more likely to corrode. I always rebuild my calipers with new pistons (stainless steel if I can find them).

 

[Don C]

Because the calipers on these cars are single piston the caliper has to float on the attaching pins to compensate for pad wear and to keep the calipers centered on rotor.

My first suspect would be that the caliper is not moving freely on the pins.

 

[Mac]

Also be aware that most rebuilt calipers do not have new pistons. As the chrome plating wears, the piston becomes more likely to corrode. I always rebuild my calipers with new pistons (stainless steel if I can find them).

The piston itself could be rusted and possibly sticking. Suggest removing the sticking caliper then opening the bleeder screw and then connect an air line to blow the piston out of the caliper. If rusted, use emery paper or scotch pad to clean up piston, then recoat with a light coating of grease and replace boot (if necessary) and reinsert into caliper. Reconnect caliper and bleed lines. Once installed, jack up entire front end of car, have someone get inside car and as you spin the wheel by hand have them hit the brakes. Wheels should stop and once the brake pedal is released, the wheels should spin again freely.

 

[Omie01]

I did check the pin float and that seems to be ok, I did regrease them when I put it back together and still no dice. I will get a pic of the rotor tonight if possible. Thanks Gents!

 

[Don C]

I did check the pin float and that seems to be ok, I did regrease them when I put it back together and still no dice. I will get a pic of the rotor tonight if possible. Thanks Gents!

You said that you regreased the pins brings up an interesting conundrum. The Ford Shop Manual says "Be sure the locating pins are free of oil, grease or dirt".

I believe this may have come about due to the limited availability of high temperature grease suitable to withstand the temperatures generated by the disc brakes and transferred to the calipers, when disc brakes first started becoming predominate. No such grease is shown in the Volume Five Maintenance Manual. Overheated grease can become as hard as a rock and freeze the calipers to the pins.

As such I have always ignored this instruction with no problems, using a disc brake lubricant such as Permatex 20353. Too many rustable metals in contact with each other, becoming locked together on vehicles not used much, for my liking.

 

[Omie01]

Well, good news gents!! I found the problem. It happened to be the inner pad was stuck in the caliper cradle! The metal backing was just stuck, I had to pry it out!! But here are a couple pics of my rotors. Does it look like the drivers side is still usable? It is a bit discolored, and the coating that was on the edges burned off. I like these rotors and would like to keep using them, but I do have a new set of normal rotors if need be. Let me know what you think. I have no experience with how hot rotors can get before they go bad.

 

[Omie01]

Don, I did not know that about the Ford manual!! I use very little brake/caliper grease on the pins. It doesn't seem like any of it came out of the boot. The pins are a very tight fit so a little lube goes a long way.

 

[Cleveland Crush]

Well, good news gents!! I found the problem. It happened to be the inner pad was stuck in the caliper cradle! The metal backing was just stuck, I had to pry it out!! But here are a couple pics of my rotors. Does it look like the drivers side is still usable? It is a bit discolored, and the coating that was on the edges burned off. I like these rotors and would like to keep using them, but I do have a new set of normal rotors if need be. Let me know what you think. I have no experience with how hot rotors can get before they go bad.

Assuming that rotor is not warped, I'd definitely take it in to get lightly resurfaced. You should be good to go.