Find a nice big open space and stomp on the brakes as hard as you can from about 40 mph a few times. When they pulled the caliper to get the rotor off they may have not supported the weight of the caliper and left it danging by the hose which could have done some damage. New stainless lines might be a good idea.

Caliper issue.

Have you checked the tire pressure ? And how new/old are your tires ?

I know it sounds dumb but if your 7/8 psi off it could pull the car.

If not that I say a bad line.

Update:

I just replaced the factory lines with aftermarket stainless ones built by Forged Performance; plus sucked out -all- the fluid and filled it with fresh Motul Dot4. Seems the problem is much much better now; to the point where I'd have to say its just about perfect. One things I did still notice is that the after a few hard stops I get out to check the termperature of my rotors with an IR Heat-gun. i find the left front is still running about 5-9% hotter than the right front, but the rear rotors now equalize in temperature.

So I'll have to give it a few days, but so far so good and the car brakes a bunch better than before. I'll probably give it just a few days and bleed the brakes one last time before I call it quits.

Either I had some air or a kink in the lines.

:tup:

Well, It's been about a year since I had to deal with this issue. To date I've done the following:

Car now has 52,xxx miles, with about 20k on the brakes.
Changed the lines to stainless and the fluid to Motul.
Bled the brakes from the caliper side of things about a half dozen times.
Bled the ABS unit one time

By now I've learned to just live with the problem, where under normal driving/braking theres not much issue. Still though, under severe braking I am able to get the front left tire to almost lock while the right is still operating at about 90%. You can imagine the car does tend to wonder/vere to the left. For the past I've burned into my brian - countersteer under hard braking - if there is such a thing. My best car buddy drove my car the other week and said he hated how my brakes react and recommended I bleed them again.

So now I'm back on top of this. Could there be a problem with the master brake cylinder not applying even pressure to both halves of the system? its about the only thing I have left to check. Also now since I have a bunch of miles on these pads; I'll probably check again for un-even wear for a stuck caliper.

Any other ideas? I found some online place which sells rebuild kits for calipers so thats a good avenue. What about master cyl rebuild kits?

Can't be the master cylinder, because it applies equal pressure to both sides of the brake circuit.

On most cars, the brakes are split in diagonals. LR with RF and LF with RR. This is so that if something happens to one corner, you still have "even" braking. Since your issues were originally with the LF and RR, I'd say you've got an issue with something after the split.

The master cyl has two outputs connecting to the ABS unit. Are both outputs in series and paths linked inside of the ABS module? If this is the case, then you are right the master has nothing to do with the issue; otherwise I do notice the master has two outputs on it.

I just bled all the pipe fittings from ABS module back to the master cyl (8 fittings total) and no difference in braking distribution. I almost want to unbolt the ABS module and level it out or even shake it a bit; bleed one more time. I'll check into this.

Another thing I notice is the F-to-R conenctor which appears to be on top of the passenger wheel well. The service manual: http://www.nicoclub.com/FSM/370Z/Coupe/2010/BR.pdf , page BR-22 is showing a physical connection labeled A or 2. I'll have to check this piece out to see if any air might possibly be trapped inside.

I'm not sure if it has helped yet, but I bled all four fittings on this connector. its located passenger side front wheel well behind the rear plastic mud guard.

http://i886.photobucket.com/albums/a...403_201254.jpg

It sucks that your are still having this issue. I feel the problem is in the caliper because you say the problem goes away when you press hard on the break, essentially setting all calipers in a uniform position. But over time the issue returns, a caliper becomes unset with the rest. As to what part is causing it I have no idea and I doubt it would be easy to notice by inspection.

2011 Nismo, actually the optosite happens. When I press the brake really hard, the front left wheel will lock before the right, and the car will tend to rotate slightly left. Light duty breaking does not always reveal the issue.

After bleeding the above connecter I think things have gotten a tad better.

I called some places and searched online, but then I totaly scored a win! I must have the best (alas RedNeck) Pawn Shop in the state just a few miles from my house. They have so many pro mechanics tools its not even funny. I picked up a ($350 - new) brake line pressure tester built by KentMoore model J-39729 for a mear twenty-five bux! What a steal. It looks the the former owner/technitian also modified these also with an on/off bleeder valve. - NICE!

Its a little old/rough, but for accasional usage I think will do just fine. I just finished cleaning it up and re-doing all the NPT fittings with new teflon and air pressure tested them acurate to 125PSI. What do you think? I'm hoping the end fitting will screw into the calipers.


http://i886.photobucket.com/albums/a...404_123404.jpg
http://i886.photobucket.com/albums/a...404_123408.jpg
http://i886.photobucket.com/albums/a...404_123421.jpg
http://i886.photobucket.com/albums/a...404_123358.jpg

Nice Find

This is what I meant about pressing hard on the break. I wasn't clear in my first post.

*UPDATE*
I think I've confirmed the problem using the above brake line guages, but just wanted to post the scenerio observed.

Rear brakes: With the car running, both guages are able to hit ~1300PSI. Both gauges react at almost the same time, in the same way/fassion. Smooth pressure rise on the guages.

Front brakes: The FR (which I believe has always been close to the worst or problem) measures fluid pressure much slower than the FL. With the engine running, the line pressure will reach ~1300 PSI on both sides, however the rising rate of the left is greater/faster than the right. Under gental brake engagements, the FR sometimes does not measure at all or takes up to 2 seconds to even poll a reading, while the FL is as-soon-as the pedal is pressed.

More observation on FR: If the brakes are pumped hard a few times, the presure seems to be get better; both FR/FL will pressure rise at the same pace after being pumped. If the brakes are left to sit for maybe 30 seconds, the FR will then start to delay in rising pressure.

Summary, RR, RL, and FL all react the same - pedal and instant pressure. FR has a slight delay of 0.5 to 2 seconds depending on pressure applied, and if pumped.

Solution: Bleeding isnt helping at all. I've literally bled about 1Q of fluid through this thing in over a year and nothing has improved.

Should I try rebuilding FR caliper? SHould I rebuild both FR/FL at the same time? Am I missing something? Right now I am thinking that since/if the FR caliper is seized, that is it retracting/reacting slowly and causing pressure to be lost inside. I'm kind of thinking a piston resisting it's new place is heading back inside of the caliper; where re-presurizing requires time for the piston to move back out in play. Does this sound correct?

Those tools look really useful, nice find!

They are being connected at the bleeder on the caliper, right?

If so then whether the caliper piston moves or not is irrelevant, the pressure within the caliper should be equal on both sides. Now, if there is a pinched line or hose somewhere leading to that FR then you would have the result you indicated, slow pressure build up in the caliper.

Chris, You could be right.

I'll try and check the brake line pressure before the calipers to rule them out - I'll take the calipers out of the loop. I'll have to come up with some adapters or bypass a line or so, but I dont see this being much trouble tapping in just before the calipers for a good test.

In google searching, seems either a restriction somewhere upstream or a faulty caliper are both culprits.