Front brakes seizing - what's with that?

[RickB]

Today when getting off the freeway my fronts were hanging, they heated up but not to the point of meltdown before I pulled off and stopped.
After a while I rocked it back and they freed up and I could drive the rest of the way home.
Any guesses whats going on here?

 

[JPSmit]

I'm going with collapsed hoses - replace your rubber

 

[Gundy]

X2 on the hoses. I've had this occur on more than one car.
It is often an internal problem and they can look fine
on the outside.

 

[Billm]

Either that (hoses) of a misadjusted brakelight switch which is holding the brake peddle on just a tiny bit and causing drag. It usually releases when the system gets cold.
BillM

 

[RichBall]

Rick

Gotta go with the hoses unless you have changed them out in the last five or so years. Used to happen with my motorhome. I'd have to go out and rapp on the caliper with a hammer every now and them to gett them to release.

 

[RickB]

Bill, is that just for the hydraulic switches?
Mine's electric, just a plunger.
I will look at my hoses, hopefully this can last till the weekend.
I'll be very careful.

 

[RichBall]

The hoses will look OK from the outside. They are double layer and it is the inner hose that is collapsing. As you push in on the brake and pressurize the caliber the hose collapses. When you release the peddle the collapsed hose does not allow the pressure to bleed off. Does it pull to one side after you release the peddle? I would think it most likely to be happening on one side, but I suppose it could be happening to both sides. I read somewhere that the hose should have a date printed on it. If it doesn't or it is over ten years old the hoses should be replaced

 

[JohnnyO]

You seriously are driving it in all this rain????!!!! Might be instant rust!! Just kidding....

 

[Billm]

Rick
The electric switch also is the end-stop for the mechanical peddle. Back it off about 1/2 turn or so and see if it fixes the problem.
If the hoses are old then it is good to change them too but the switch adjust could easily be the problem at the moment.
JohnnyO- Rick drives it everyday, rust or no!!
BillM

 

[SilentUnicorn]

i beg to differ- i have gone thru two brake switches by letting them be the pedal stop. Granted they were cheaply made switches. The ends got beat on by the pedal and mushroomed them to the point they would not work at all (sticking). I now make sure the switch is not the stop. haven't lost a switch in 3 seasons.

m

 

[RickB]

Easy enough to back the switch off a bit, I can try that today.

Yes - I drive it every day (unless for some strange reason I simply don't drive at all for a day - rare). You can keep ahead of the rust if you are diligent.
There is a bit of surface rust in a couple spots, if I get a day when there's a bit of sunshine and I think of it I can sand it down and slap a bit of rustoleum paint on the spot. Frankie is not a trailer MG so he doesn't mind.

The hoses were on the car when I bought it, so it very well could be them.
Both front brakes are seizing at the same time.

If it was the switch interfering wouldn't I notice the pedal catching?
The only thing I'm feeling at the pedal is a harder resistance higher up the travel - normally I can press down an inch or two but when this happens the pedal is hard near the top of the travel.

 

[Spridget64SC]

Have seen the brake light switch threaded body interference a couple times. Bad hoses as well. Another rarer situation is if you have an aluminum body master cylinder and get corrosion/crude hanging the push rod cup up in the bore. Whichever the case, it comes down to the fluid in the caliper not being able to return up the lines and back into the master cylinder once the pedal is released.

The switch is at the front of the pedal box and acts basically in an off/on mode. It has a little plunger up a hollow threaded tube the operates the actual switch mechanism in the rectangular body. When you step on the pedal, the pedal itself releases the plunger as the top of the pedal/pushrod moves into the master cylinder. The reason the pedal feels hard during this condition is that the brakes are already "On" due to the hydraulic lock of the fluid in the system.

HTH,
Mike Miller

 

[RickB]

Mike, so if I follow this correctly the plunger might be sticking out pushing the push rod in a bit and that could cause this.
I've had the plunger switch fail before but that was different, it also did not start acting normally after a bit.
I definitely have to dig into this and find out just where this is failing.
It's hard to believe both hoses would fail simultaneously - so what's farther up the fluid stream that could cause both front brakes to lock? MC could be, but it was installed new last summer.
I have to dig into the system and find out what's at fault - it could be both hoses and they are old so they should be replaced anyway. I want to fix the problem though and not just start replacing stuff until I get lucky.

 

[Sarastro]

I've had the brakes hang up simply because they were adjusted too close. Now I back them off an extra "click" beyond the standard adjustment setting.

 

[RickB]

Front discs, no "click" available...

 

[Spridget64SC]

With a new iron master cylinder, it could be rust/corrosion in the end of the cylinder keeping it engaged. Like what I described above for the aluminum cylinder. Also, if there is an adjustable pushrod for the brake pedal to M/C connection, it could be too long, doing the same kind of thing when everything gets warm and heated up. When the brake fluid gets hot, it will expand and push back up the line as well. I would agree with chasing all the possible causes before replacing something.

Mike Miller

 

[RickB]

Then why does rocking the car back free it up so I can drive again? Stepping on the brake doesn't seize it up again after this. Until I am coming off the freeway that is.

 

[14dna]

Rick;

My first guess would be the hoses, but have you checked to see if the pads are seizing in the mounts on the calipers?
I have seen many a car have front brake problems with the pads corroded.
Worse on a freeway because brake temps go up.
It can be fixed with cleaning,(read no money) so good place to check.
Just trying to cover all bases.
Good luck man, it shouldn't be too hard to find.

Dave

 

[RickB]

Thanks I will also look for that!

 

[Spridget64SC]

Could be the brake pad's backing plate sticking in the caliper or spring clips. Also, I've seen the caliper pistons hang up due to being extended almost to the limit from pad wear. Cleaning should fix the caliper issue. Renewing pads will fix the caliper piston extension. Just keep looking till its found.

Mike