StygianMax

iTrader: (8)

Can anyone explain to me how the rear caliper releases pressure from the piston when the e-brake handle is dropped? Is there some sort of a valve that allows brake fluid pressure to be relieved?

When I drop my e-brake handle, the driver set of pads are still grabbing onto my one rotor. I haven't figured out for the life of me why that is. What I do know is:

- e-brake cable is fully functional
- caliper pins slide freely & there's no air trapped inside "cylinder" or space that the pins slide in/out of
- small hole (~1.5mm dia. in the brake piston boot) located by the middle i.e. not edge of boot so there are no sign of brake fluid leaking

Any brake gurus out there?

Matt93SE

iTrader: (44)

the parking brake doesn't use fluid pressure. it uses tension from the line to turn a screw inside the caliper, which turns and mashes the piston into the pads/rotor.
when you release the tension on the cable, it's supposed to turn back enough to remove the pressure, but evidently it's not.

I'd look at a rebuild kit for the rear calipers, or buy another caliper. the rears aren't much fun to rebuild because of the parking brake stuff.

Edit: is the piston frozen in the caliper?
try getting the caliper off the rotor, then pull the parking brake. does the piston move at all, or just stay where it is?
sometimes the tiny hole in the boot like that can cause the piston to form a little rust on it and sieze to the caliper body. just another suggestion. don't try that unless you have another car to drive in case you can't get the caliper back over the rotor.

StygianMax

iTrader: (8)

That's one of the problems I suspected but because I really don't know enough about the inner workings of the caliper with the e-brake, I posted the question.
No, it moves freely.
I pulled it off this weekend with a couple other local Maxima buddies helping. I have a piston turning tool which can easily turn the piston back into the caliper.
Hehehe....my pads are grabbing so tight that when I'm in neutral, I can't even roll down a gentle slope.

Here are some pics that I took from Saturday's work:


Below: Orange arrow points to springloaded pivot arm that was not able to move freely. I used penetrating oil to break up any corrosion that was binding it.


Below: Since the arm was impossible to move by hand, I used my ratchet to turn the arm fully clockwise, then ccw, etc. to allow the penetrating oil to do its work. I only looked at the arm & did pay attention to anything else that was going on...and guess what happened?


Below:....the whole piston came out an dsome brake fluid started leaking out! DOH!! The piston went back in easily enough with the piston turning tool.


The final step was to bleed the brake lines to rid it of air bubbles.

The e-brake cable is intact and the caliper pins both slide freely.

If you have any more questions/insights, I love to hear them!! My Max is with the dealer right now so I'm waiting to see what they report back on. I've shared with them all the info I posted here so hopefully they won't try to scam me.

Thanks Matt93SE for your help!

p.s. I love your cardomain page & ride!! Sweet brakes & Corbeau seats....***drool***

Thaniel

Buy a set of rebuilt calipers from an auto parts store. I put a set on my '87. Don't remember the cost but it wasn't all that much. From the work you show in the pics, swapping the calipers would be easy for you.

StygianMax

iTrader: (8)

I just got a call back from the Nissan dealer. They recommended getting a re-built caliper which sounds reasonable to me. As the pads are binding the rotor pretty tightly and can't drive the Max home safely, I'm just going to have the dealer do the work. I get a nice clean re-built caliper which I can paint with my leftover Foliatec paint so that's cool by me. Minimal prep work required there.

Oh yeah, while I was driving the Max to the Nissan dealer, my ABS light came on, I guess an ECU reset would clear that ....I hope. I don't really want to hear that an ABS sensor got toasted (literally!) They mentioned my pads were crumbling too...must have been the high heat build-up. Good thing I have a spare set of rear pads to replace them with.

Thx for your insights!

Matt93SE

iTrader: (44)

there's something of a ratcheting system inside there that allows the thing to decompress when you let off the parking brake. since the parking brake itself was rusted up, I would suspect that something internal to that stuff has some rust damage too.

you've got a couple options:
1. rebuild the caliper for $45 and hope it fixes the problem
2. buy a reman caliper from auto parts store or a dealer.
3. buy a used caliper from a junkyard.

personally, I've got no problem buying junkyard parts, BUT you might wind up in the same situation you're in now. unlikely though if the car is in good shape.

btw... that's a lotta rust on that caliper! (then I noticed you're in Ontario. why am I helping a damn Canadian?! )

My suggestion would be to replace the caliper- whether you buy used or new/reman is up to you. but I think it'll be easier to do that than to rebuild the rear caliper and be out a couple hours of work and the $50 for a rebuild kit... only to find out it still doesn't work.

Matt93SE

iTrader: (44)

okay, nevermind. replace it.

StygianMax

iTrader: (8)

Yep, I agree.

No no, I'm from Ontario, California.....j/k eh!! hahaha