I'd recommend replacing them with new (rebuilt) units. Only problem was the price jumped from (1993) $100/exchange perside to something like $250 per side! OUCH! Ross Mullen, Sports Imports, had some units up in Canada that he was selling at the US$120, not sure if any are left (1993).
If You Rebuild Them (worth a try)
Use a 7/16" flare nut wrench (my 11mm fits just fine!) on the nuts to loosen them. Sometimes soaking them a day before with penetrating oil will help.
Note the bleeder screw hole, interconnect holes, and brake line hole are DIFFERENT. Take the time to do one side at a time, and pay attention to inner and outer calipers. It is easy to get confused, but perhaps making a little mark with a center punch (one dot, two dot...) will help when it is time for them to go back together. I have a special machinist paint... but brake fluid will remove it! ;-(. Lines will thread into the "wrong hole" but the end of the metal flare will not seat correctly, crushing the line and resulting in a leak.
Make sure the bleeder screws will loosen first. (Nothing worse then doing a full brake job, only to discover the bleeder is frozen, and snapped off when you go to bleed the system).
How do I get those pistons out of the housing?
To remove the pistons, it is best with hydraulic pressure. By doing 'on side at a time' you can remove the caliper, and use a "C" clamp to hold the outer piston and pump away on the brake pedal until you hear a 'poof' as the piston comes out. Carefully slide it back in a little, and use the C-clamp to hold it... leaving the outer piston free... and pump again. Pop, out it comes! Yep, put down a container so the old brake fluid can be collected and taken in to a hazardous depot. Nasty stuff, does not belong in the trash!
[Having said the above, I have and old broken metal line that I use to 'plug' one hole got the outer piston... then use air pressure *** use extreme caution, start with a low 20psi setting *** to force the piston out. The inner piston assembly has the bleeder screw, which just leave in place]
If the pistons look good, but only the caliper bores were pitted: I'd check into sending them to White Post Restorations [Need address, phone number, and current price] , to be sleeved.
It the pits are MINOR, then you should be able to get away with using really fine emery paper to remove and sharp edge, and rebuild them with the caliper kits from Nissan. The parts guy will go crazy, as there is not a rebuild kit listed for the roadster... BUT, the very first 240Z's off the line have the same calipers (this was only for the first couple months production), hence the part number appears in the 240Z section (which I think was listed as a 1969 production date!). [I'll supply a # as soon as I get all 60 "garage" boxes unpacked!)
With minor pits, the worst case is a seal starts seeping. Admitted a pain, especially when you need the car for work, but keep an eye on the brake fluid level and you shouldn't have any problem.
TIP: While rebuilding the brakes, clean all the crud out. If you use solvent to clean everything, give it a final rinse - or two - with alcohol to remove all traces of the solvent.
On the caliper, clean that leading edge well. Dunk the whole seal into brake fluid before sliding it into place. The kits have some "brake grease" which I highly recommend. It is easy to rip a seal putting everything together, so use patience when sliding it in. Bummer to see fluid on the garage floor when backing out. Worse is the seals come in packs of four!
Metal Interconnect Lines
There is a metal line that connects the two pistons. If there is a black plastic 'protector' on them... REMOVE IT! It will turn acidic with age, and combined with moisture, will rust right through the metal!
Use caution on removing and replacing the lines. If they are bent, the wheel's rim may rub against them, effectively cutting it in two.
We still have not seen an official specification, but new it seems rotors were either 0.400" or 0.380" thick. Once a rotor is turned, and the pads are worn down, there is a good chance of the pads not being "thick" enought to work! The caliper, and everything else is fully functional, but the piston will contact the metal support form and push against that... while the pad just 'sits there'. Only cure is new rotors! :-( [This has stumped quite a few as to why their roadster had 'horrible' brakes!]
Repacking the Wheelbearings
When you pick up the caliper kit... don't forget front wheel bearing seals.
With the front calipers off, it is a little easier to do it now! The original manual specified repacking the bearings at something like 6,000 mile intervals. Still not a bad idea, but I think the current "high temp - for disc brakes" bearing grease is probably good for 25,000 miles... unless you auto-x, or do a lot of water crossings!
Bleeding the Brakes
OK, you remembered to loosen the bleeder screw. If you use a vacuum pump to bleed them... wrap the bleeder screw with a turn of teflon tape.
I usually just do them by myself, but placing a long tube that fits tightly over the bleeder, and looping it up and around the suspension (higher than the bleeder), and putting the end into a container (keeps the mess minimized). Biggest problem is to remember to refill the master cylinder before running it dry!
I wrote this up a while ago, and it still holds true. ;-) I have not had the time to dig through the boxes to findpart number of the front brake kits... but do recall it is NOT listed in the Datsun Roadster Parts book... but the first month of 240Z production used the same brakes! I bought a kit for $25 or so (does all four pistons):
A Note from Scott Higashi
I have a box here on my desk containing the caliper rebuild kits. It is Nissan K-SEAL T19 Part no. 41120-73425. It contains the boots, seals, retainers, and new star washers for both sets of
©1996, Thomas Walter