Front brakes locked

[thetimanator]

Last week I upgraded to 280zx struts/brakes. http://community.rat...roke-something/

I still have drums in the rear so I stuck with the 510 master cylinder. Last night driving home, I let off the gas pedal and the car felt like the brakes were being applied. I went to pull over and applied the brakes and the pedal was super stiff. When I finally got pulled over smoke was pouring out of both wheel wells!

 

I tore it all apart this morning and you can see where the pads were stuck on the rotor. I had to open the bleeder in order to get the caliper off. I have rebuilt calipers that I was going to put on this weekend anyway, but I'm starting to think that the master cylinder got stuck or something. What do you guys think?

[paradoxx]

maybe the seals on the calipers got stuck? Only the front wheels were stuck or the rears also?

[Kisor]

Put it back together and pump it up, check to see if they are sticking again. If so, loosen the line where it goes to the rubber hose, body side. If it releases the brakes the hose is prob ok... Its just good practice to start at the problem and work your way back to the master when diagnosing brake issues.

 

If you get all the way back to the master and its still sticking, check the rod adjustment at the pedal to make sure its not keeping the brakes applied. If all checks out its prob a master issue.... I've seen too many people throw master cyls at cars thinking its the culprit and it ends up being something else.

[MicroMachinery]

It's a master cylinder issue. Either the MC itself, or I've also seen the little screens inside the reservoir get pushed too far in and block fluid from returning.

[thetimanator]

maybe the seals on the calipers got stuck? Only the front wheels were stuck or the rears also?

 

 

Just the fronts. And it was definitely both sides of the front.

 

Put it back together and pump it up, check to see if they are sticking again. If so, loosen the line where it goes to the rubber hose, body side. If it releases the brakes the hose is prob ok... Its just good practice to start at the problem and work your way back to the master when diagnosing brake issues.

 

If you get all the way back to the master and its still sticking, check the rod adjustment at the pedal to make sure its not keeping the brakes applied. If all checks out its prob a master issue.... I've seen too many people throw master cyls at cars thinking its the culprit and it ends up being something else.

 

hmmm, both sides were definitely locked at some point. Wouldn't it be weird for both sides to lock and both brake hoses to be the culprit? i guess stranger things have happened. The rubber hoses look relatively new. Something of note, when I was removing the wheels, one side was still locked while the other was not. Not sure if that means anything though.

[Kisor]

It's a master cylinder issue. Either the MC itself, or I've also seen the little screens inside the reservoir get pushed too far in and block fluid from returning.

 

Or you could just throw some parts at it.....

 

Just the fronts. And it was definitely both sides of the front.

 

 

 

hmmm, both sides were definitely locked at some point. Wouldn't it be weird for both sides to lock and both brake hoses to be the culprit? i guess stranger things have happened. The rubber hoses look relatively new. Something of note, when I was removing the wheels, one side was still locked while the other was not. Not sure if that means anything though.

 

That sounds more like a hose issue.... I'm not diagnosing your problem, I'm suggesting tests to help you figure out whats going on.

 

 

Quick and easy, crack the line at the other end of the hose and see if it releases like the bleeder did. If your bleeders released them its not the calipers. If the line releases them its not the hoses... work your way back.

[MicroMachinery]

Or you could just throw some parts at it.....

 

I'm all for proper diagnosis, but I must disagree with that(rather bold, I might add) statement: It's only "throwing parts at it" when you don't know what you're doing. There are some people out there who have experience, and can call a Spade a Spade when they see it.

 

To the OP, go ahead and follow this guy's steps for diagnosis, eventually you'll find your problem. I just know that given the information provided, what the problem is. Better to be safe than sorry, but I just thought I'd save you some time. Happy Hunting.

[datzenmike]

hmmm, both sides were definitely locked at some point. Wouldn't it be weird for both sides to lock and both brake hoses to be the culprit? i guess stranger things have happened. The rubber hoses look relatively new. Something of note, when I was removing the wheels, one side was still locked while the other was not. Not sure if that means anything though.

 

 

It sure does. I just read this after writing a paragraph about why it's the master cylinder. If one had released then trapped hydraulic pressure must not be the problem.

 

Where did you get these struts? Did you replace the pads with new? If they are old or poorly stored the pistons may seize in the bores. Brakes go on and stay on. My Sundance had one seize, smelled like a burning clutch. Pulled over with smoke coming from the wheel well. I got out and you could feel the radiated heat on your face. Threw snow on the rim and it boiled it was that hot. I got the rim off and pried the caliper with the tire iron to retract the piston and free the pads from the rotor. Had to pump the peddle several timed to move the piston back against the pads again and drove it, checking a few times, but it was fine after that. I replaced the rotor and pads so it wouldn't happen again.

[MicroMachinery]

I didn't read that last line Mike had highlighted. It certainly could be a combination of a couple things. Let us know what you find out.. sounds like a sticking caliper on one side at least. I think rebuild kits are under $10/pc, wouldn't hurt rebuild them both and have peace of mind about your calipers.

[docbainey]

Like's been said look at the rod that actuates the master cylinder, attaches to the brake pedal, if the jam nut has come loose that could be your issue, or just rusty crappy calipers that need rebuilt.

 

Stuck on brakes are alot better then no brakes!:o

[wayno]

Last week I upgraded to 280zx struts/brakes. http://community.rat...roke-something/

I still have drums in the rear so I stuck with the 510 master cylinder. Last night driving home, I let off the gas pedal and the car felt like the brakes were being applied. I went to pull over and applied the brakes and the pedal was super stiff. When I finally got pulled over smoke was pouring out of both wheel wells!

 

I tore it all apart this morning and you can see where the pads were stuck on the rotor. I had to open the bleeder in order to get the caliper off. I have rebuilt calipers that I was going to put on this weekend anyway, but I'm starting to think that the master cylinder got stuck or something. What do you guys think?

 

I have a feeling it has something to do with the M/C not matching the brake system anymore.

Did you have drum brakes in the front before the upgrade?

Do you have a double or single M/C reservoir.

Here's the thing, master brake cylinders have a residual valves built into them, so if you have drum brakes all around, it keeps 10lbs of pressure on the drums all the time, if you upgrade to front disc brakes, which need only two to three pounds of pressure, the 10lbs builds up to the point where either the fronts seize, catch fire, or lock it up so tight that you stop moving or you break something like the u-joint, or worse.

In conclusion, if you had front drum brakes, and now you have front disc brakes, you have to tear the residual valve out of the M/C, or you need to change to a dual master cylinder that is for a front disc/rear drum brake system, I used the 1979 datsun 620 M/C in my 521, as it was easy to get, a lot of guys are using the 1979 280 ZX M/C I beleave.