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PostPosted: Tue Jan 07, 2014 7:10 pm 
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Joined: Tue Dec 17, 2013 4:29 am
Posts: 59
Location: New Mexico
I'm a 240z guy that drives a Z31 and I don't know much about them especially when it comes to a mechanical problem that I have never seen or felt before. Here it is:

About 80% of the time the Z drives fine, but with the other 20% things start to happen that aren't normal. When I'm driving into town I will get about 5 miles into the drive and all of a sudden the car will start to shake, lightly at first and then it builds to a heavy shake. The steering wheel shakes a lot and I have to hold it pretty tight. I have checked all the usual things and there is nothing wrong. The symptoms that are noticeable is that the brake pedal becomes hard when you push on it and there is a slight burning smell when I get out of the car. If I park the car for a few minutes and restart it, everything is back to normal and the rest of the day driving it is fine. I can push on the brake pedal and it is back to normal as well. When this problem does happen it feels like the brakes are slightly on because the car is sluggish while driving until I stop. Almost like the e-brake is on halfway. It happened again in the drive into town today but never happened again after the first stop. Does anyone know what this is? Lugs are tight, alignment is fine, tires are good.


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PostPosted: Tue Jan 07, 2014 10:55 pm 
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Joined: Sat Feb 16, 2013 3:42 pm
Posts: 282
Location: Rochdale, MA
I would check to see if one of your calipers is hanging up. Next time you take it out for a ride and you get these symptoms stop the car and place your hand on each wheel. See which wheel feels warmer. That is the one that is hanging up. I am sure you can ask Frank about hanging calipers. He battled a nagging caliper for a long while on his 240Z.

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Adam Perry
Datsun 260Z
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PostPosted: Wed Jan 08, 2014 11:58 am 
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Joined: Tue Dec 17, 2013 4:29 am
Posts: 59
Location: New Mexico
what causes them to hang up?


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PostPosted: Wed Jan 08, 2014 1:09 pm 
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Joined: Sat Feb 16, 2013 3:42 pm
Posts: 282
Location: Rochdale, MA
When calipers get old the pistons inside the caliper may get corrosion and cause it to stick. Couple ways to fix it. Either rebuild the calipers with new pistons and seals or buy a caliper already rebuilt.

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Adam Perry
Datsun 260Z
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PostPosted: Wed Jan 08, 2014 5:21 pm 
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Joined: Wed Jul 23, 2008 2:38 pm
Posts: 3098
Location: rhode island
Take a hammer and go underneath, and you will see the ebrake cable in the bracket......hit the leaver to see if it frees up. Your car should be able to push around in neutral, if not, your brakes are stuck. If the common ebrake isn't the issue, then there is a caliper that is no good. Another thing not to over look is a collapsed brake hose.


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PostPosted: Wed Jan 08, 2014 5:26 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 12934
Location: CT
Quite right.

Mine was cured by replacing my neoprene brake line hoses with steel flex lines ($60).

And change the brake fluid if it looks more like strong tea than like white wine.

My caliper piston was hanging up and it didn't take much to fix it. A bulging brake line hose caused the pressure behind one piston (brake puck) to not release like it should when I took my foot off the brake. That one piston remained partially "deployed", rubbing against the turning rotor. That give me a solid drag on one side, and overheated the caliper. It also made the steering wheel oscillate as if one wheel was out of balance.

Heat-expanded parts further reduced the clearances until I had one brake fully ON while the other 3 were off. When I parked awhile, the bulging brake line hose relaxed, letting the pressure off and released the stuck puck. I could climb in and drive normally until it happened again.

Careful about feeling the wheels. I left a lot of my fingerprintZ on the faulty rotor. I'm talking INSTANT white-ash skin from just a quick dab on the rotor. You won't do it twice, believe me. :roll:

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1970 240Z


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PostPosted: Wed Jan 08, 2014 7:17 pm 
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Joined: Sat Feb 16, 2013 3:42 pm
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Location: Rochdale, MA
Frank...I stupidly did the same thing and touched a rotor with the back of my finger. Boy was that a mistake. Touching the wheel will not burn you but you will be able to tell the difference in temp with the one that's hanging up.

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Adam Perry
Datsun 260Z
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PostPosted: Wed Jan 08, 2014 7:25 pm 
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Joined: Tue Dec 17, 2013 4:29 am
Posts: 59
Location: New Mexico
This happens when I'm not using the brake. I hardly ever use the e-brake.

It kicks in when ever it wants, usually once and then it doesn't happen again. It looked like the drag feeling was coming from the rear pass side. I changed the pads this weekend and nothing looked out of the ordinary. And yes, the steering goes crazy and when I put on the brakes the car chatters to a stop and again never happens after that. One other thing I noticed is it seems to happen after I have been going at a faster speed for a period of time, hardly ever when driving in traffic.


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PostPosted: Wed Jan 08, 2014 8:05 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 12934
Location: CT
Hmmmm, curiouser and curiouser.

I realiZe we're talking two different cars here (my experience is with the 240), but generally, if a problem is in the front axle you will feel it thru the steering, and if it's in the rear axle you'll see it in the vibrating rearview mirror. I know it sounds stupid, but does your mirror vibrate noticeably when you get this sensation?

I'm picturing one of your rear calipers hanging up the way we described above. At low speed you probably wouldn't notice it much, but at higher speed it would act as an unbalanced wheel (quite noticeable). As you drove the car at highway speeds, the slight rubbing of the brake pads against the rotor would generate higher heat on one wheel than on the other three, so when you hit the brakes, you would get 3 cold pads trying to stop 3 cold rotors, and one HOT pad trying to stop one HOT rotor. The car would shudder and buck just the way you described.

By changing the pads you wouldn't see anything amiss. The offending brake line would be relaxed and look exactly like the others, because the whole car is cold and you haven't used the brakes yet. I suppose if you mic'ed the rotors and the old pads, you might find a measurable wear on the side which drags.

And don't dismiss the handbrake altogether, either. As Paul suggested, it might still be the culprit. The Z31 cables are different enough from the S30 cables so that I don't know enough to discuss it. There might be some way in which the Z31 handbrake could be causing this issue for you. (Z31 guys? Any input?)

And one final biZarre thought ~ snow in your wheels might give you the sensation of an unbalanced tire. My wife this past week complained that the family SUV was dancing all over the highway at speeds above 50, but acted fine at lower speeds. I found a clump of snow packed into the 'spokes' of one rear wheel. Cleared it out and her complaints stopped immediately. Most of us don't drive our Z during winter, but it's easy to imagine how a 6-oz clump of ice/snow packed into one side of one wheel could throw the whole car around at speed.

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1970 240Z


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PostPosted: Wed Jan 08, 2014 10:44 pm 
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Joined: Sun Apr 01, 2012 4:19 pm
Posts: 1644
Art, may I suggest a visit to z31performance.com??

If you don't want to make a log in, let me know and I'll ask the question for you.

They're also on Facebook!


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PostPosted: Thu Jan 09, 2014 5:57 pm 
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Joined: Wed Jul 23, 2008 2:38 pm
Posts: 3098
Location: rhode island
Sounds like sticky brakes. I mean we are not talking some running problem here, just to be clear. How about doing a front brake job and see. You need to make sure caliper piston slides in nice with some pliers or c-clamp works, I got the actual tool. (mostly I use pliers.) The caliper SLIDES have to MOVE. and the Brake pads should SLIDE out easy, if you have to PRY them out, that's another problem. Last Issue is a collapsed brake hose. I think I can say "Period" at the end of that. //see me in brakes pt2 Rotors. :wink:


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PostPosted: Fri Jan 10, 2014 3:34 pm 
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Joined: Tue Jul 23, 2013 6:37 pm
Posts: 20
Location: Enfield, CT
Paul is correct in re the caliper slide pins. This is a common issue with Z31's. The slide pins lose their lube as the rubber booties degrade or leak. The pins rust in place and the pads and pins bind causing drag on the rotor. The booties and the pins are a common replacement item and are available at your local Napa, etc. or ebay. Pins, booties, and some high heat brake lube =< $30 for 4 corners.

Front brakes = wheel wobble, etc. as artzccm described
Rears= often huge noise from RR, particularly in reverse. Mimics ebrake drag.

Been there, done that.

86NA
88T


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PostPosted: Fri Jan 10, 2014 3:45 pm 
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Joined: Tue Dec 17, 2013 4:29 am
Posts: 59
Location: New Mexico
So I should be able to check each one without having to remove the caliper from the hub right?


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PostPosted: Sat Jan 11, 2014 9:04 am 
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Joined: Wed Jul 23, 2008 2:38 pm
Posts: 3098
Location: rhode island
You might be able to take a screw driver and you can actually slide the piston back in the bore, now you should be able to grab the caliper and slide I back and forth. That wont tell you the pads are stuck though. I would just plan on redoing the brake job. Maybe someone put NAPA pads in there, which BTW, don't use them, they don't fit correctly, and I have been through this issue for a long time, and it's still not resolved. They are too tight and will burn up the brakes. I had a so called caliper seize some years ago with my truck, delivering Z parts in Jersey, well I'm in the rest stop, got the caliper off, piston slides in good, the slides are good, and there are my brake pads from PO, stuck in the holders. I had to pound them out, then file down the flanges, using the curb, because file is the one tool I didn't really think of bringing. (plus I got this cop in his car observing all this,) I used chassis grease for that was all I had "Hanging around" on suspension components. That worked fine until I finally replaced with a fully loaded caliper from Rock Auto for $20. That's right, $20. Caliper with pads. BTW, turning old Japanese rotors I suggest, because the metal back then was better than now. EX: My 240 original fronts are still shinny, but the backs I got from MSA are showing surface oxidization already. :cry: They don't make things like they use to..........How many times we say that. :roll:


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PostPosted: Sat Jan 11, 2014 11:05 am 
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Joined: Tue Dec 17, 2013 4:29 am
Posts: 59
Location: New Mexico
When I changed the pads on the pass rear, the one I thought was the problem, the piston retracted smoothly (I have the tool that makes it easy to turn back in).

Last night I was driving home (about 20 miles) and this time nothing happened. The car drove fine all the way home. The only difference from other times is that it was about 20 degrees cooler. Mean anything? I promise, this will be the last question.


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