brakes sticking

[zak]

Hello all, I had an odd thing happen to me on Saturday as I was bombing around in my 250 SL , 4 spd.
During a stretch of spirited driving with heavy braking my brakes began to stick. It was subtle at first, then it got more pronounced. When I stopped the car on an incline it would not roll at all.
So I turned around and headed home. By the time I got there I was driving in second gear at 4500 rpms just to crawl along. As I pulled into the garage both front brakes smoking, the front steel rims were hot as a pistol and the smell of hot brake pads filled the air! But the rear brakes were fine. it was odd that both front brakes locked up. The brake pedal seemed stiffer and there was less pedal travel when this was going on. brake fluid looked clean and clear when I checked after all cooled down.

Just last summer I had the brake system rebuilt, about 500 miles ago and all was perfecto. I could stop on a dime.
 - New rotors, pads,  hoses, had the calipers repainted and rebuilt -   

So after talking to my local guru mechanic ( not the guy who did the brake job ), because it was both front brakes the fault was narrowed down to either a faulty master cylinder or brake booster.
So the next day I disconnected the booster hose and plugged the vacuum line and went for a drive and all was fine again. I drove the car hard for over 10 miles on hilly roads and no brake failure. So the booster was hanging up. Funny thing now is that with the brake booster disconnected the engine seems to run better, smoother revving, faster response, a bit more power even.

So now I will look to get the booster rebuilt this winter while the car is dormant and meanwhile drive with the manual brakes.

jz

 

[stickandrudderman]

I worry about the sanity of anyone who willingly drives a car on a public road with knowingly defective brakes.

[MikeSimon]

it could be the bleed orifice in the brake master cylinder. When you use the brakes excessively during a spirited drive, the system and the fluid heats up. It needs to expand and usually does it through the return bleed hole in the m/c. If this is plugged, the pressure goes against the pads and they lock up.

[Benz Dr.]

I worry about the sanity of anyone who willingly drives a car on a public road with knowingly defective brakes.

Yeah, that's kind of what I thought too. If I recall correctly, you would have pretty much no brakes at all with vacuum disconnected.

[zak]

Thanks Mike. I will scope out in the master cylinder bleed hole.
Come on guys, the manual brakes with the vacuum line plugged perform very well.
The comment that I will have pretty much no brakes at all with vacuum disconnected is respectfully,  incorrect.
Have you ever tried driving with booster disconnected ?
The stopping power is strong as long as you apply a bit more foot pressure to the brake pedal.

The fact that the engine runs better with the booster disconnected is an interesting side effect. The booster may have a vacuum leak that causes less then optimum performance
I don't know.
Anyway, I appreciate your concerns and responses.
thanks,

jz

[Benz Dr.]

Thanks Mike. I will scope out in the master cylinder bleed hole.
Come on guys, the manual brakes with the vacuum line plugged perform very well.
The comment that I will have pretty much no brakes at all with vacuum disconnected is respectfully,  incorrect.
Have you ever tried driving with booster disconnected ?
The stopping power is strong as long as you apply a bit more foot pressure to the brake pedal.

The fact that the engine runs better with the booster disconnected is an interesting side effect. The booster may have a vacuum leak that causes less then optimum performance
I don't know.
Anyway, I appreciate your concerns and responses.
thanks,

jz

Uh, I'm going to respectfully disagree, STRONGLY!!  This system is designed to run with a vacuum. Oh, you'll have to push harder alright. Like your whole body weight harder.

If your engine runs better with the hose disconnected that's an indication of a vacuum leak. It is NOT, in my opinion, an indication that your brakes will be better or that the car would be safe to drive.

It would be highly irresponsible for me to indicate anything otherwise.

[zak]

Dan, I appreciate your honest comments and meant no disrespect to you and other experts.
Yes I agree , the car brakes much stronger with the booster/vacuum connected.
Based on your cautionary comments I plan to get the booster rebuilt asap.

Can anyone recommend a rebuilder near the general NY area pls ?
Thanks,

jz

[Benz Dr.]

Hey, no problem. I just don't want to see you or anyone else get hurt.