Rebuilding the front calipers on an old Datsun is a time-consuming but economical alternative to buying new ones.

"Marilyn", my 67.5 SPL311, had a couple leaking rear wheel cylinders, which I replaced a month back. However, as with any system, replacing one component simply reveals the next weakest link - Her front brakes were just not performing properly, and closer inspection revealed bad things.

Both front brake calipers were leaking slowly, and brake fluid was getting on the inside of the front rotors. Not good. Time for an overhaul.

We're working with a 42 year old car here, and many of the components didn't look like they'd ever been replaced.

Older Datsuns often had a multi-part caliper. That is, the brake cylinder and piston assemblies are seperate from the caliper - We'll look at this in more detail soon. You can certainly buy rebuilt front cylinders, but they're not cheap. In fact, I was looking at nearly $800 for all four. OUCH.

A rebuild kit is $43. How hard can it be?

Answer? Not hard. Just tedious and messy. Have TONS of paper towels, brake cleaner, Purple Power, some wire brushes and a couple old towels on hand. Let's get started.

If you're not pretty accomplished with tools, you'll probably want to abandon any fantasy of doing this yourself. I know my way around the garage pretty well, and this one was a challenge for me.

Once you've done the obvious (get the car in the air, pull the wheels off, lay out your tools, etc), you're going to want to drain the brake master cylinder. I was rebuilding mine, so it was already out, but I still sucked all the fluid out first (less mess, less cleanup). A turkey baster or big ol' syringe works fine.

Here's a look at the factory calipers for the front:







Remove the caliper from the back side of the hub (Nissan hasn't changed this in 50 years). As you can see, the cylinders bolt to the sides of the caliper frame itself. Remove the 4 bolts holding the assembly together, and here's what you've got:





Note: Do one side at a time. No sense getting these things mixed up. Pay attention to the orientation of the crossover line as well.

These things fail because of two reasons: One, brake fluid over time absorbs water, which corrodes the cylinder bores and causes pitting, which allows brake fluid to leak past the seals. Two, the seals harden and deteriorate, accelerated by contaminants in the brake fluid. Forestall this by changing your brake fluid annually. Some will say this is overkill. To them I say, "You're lazy. Have fun rebuilding your brakes."

Time to get the piston out. Here's where things get hairy. You're going to blow the pistons out with compressed air. Some folks will advise all kinds of fancy safety features here. Not me. Put the entire assembly in a trash can... hang the brake hose over the side, cover the whole thing with a nasty old towel. Wear eye protection and gloves. Put the rubber tip on your air gun, stick it in the brake hose, hold 'em together, turn your head away and squeeze the trigger. I used 100 psi. You'll hear a *POP* as one piston comes out. DO NOT look at what's in your hand, because brake fluid will now spray back out of the hose.



Set the air nozzle aside and retrieve the one piston. Place it on your bench with a note identifying it as the INNER or OUTER piston. This is important, there ARE differences. Undo the brake bleeder screw on the other cylinder, insert your air nozzle, and blast away. Again, *POP*, retrieve, label, and clean up your mess.

Here's what the piston looks like:







And, here's a look at the cylinders:





See the pitting and corrosion? Bad news. See the deteriorated (more like shredded) seals? Mo' bad news.

Get the old rubber off the piston. There's a round flat seal and a bell-shaped larger seal. Clean out the grooves and scrub the piston down with degreaser and a wire brush. Set them back on their labels (don't get 'em mixed up).

Now, clean the cylinders real good. We're gonna tackle those pitted bores. I used a... aw, hell, what's it called... the round thing with flaps of sandpaper on it that goes in a Dremel? Flappy Sander Wheel Thingy! YEAH! 200-grit, please. Be gentle, you DO NOT want to get the cylinder bore out-of-round. Do a little at a time and keep even pressure. Wipe the bore frequently with a towel dipped in brake parts cleaner to check your progress. Then, move on to a 400 or 600-grit, and finally, take some 1000-grit to it (I did that part by hand, not using the Dremel). You can polish the bore with progressively finer grit if you'd like.

Here's the deal - This is Flintstones-era technology. This ain't an F1 car. Anything is going to be better than the mess you saw in the pics above, so use your best judgment.

Here's mine during and after cleaning up the bore:





Once you're done, clean the whole assembly thoroughly with brake parts cleaner, taking special care to clean the tiny bypass holes inside (see them in the pic above). I even flushed out the brake hose itself. I then painted the assembly to prevent rust and to make it look nice.

Now, put your new seals on the pistons. It's pretty self-explanatory, and here's what the rebuilt piston will look like when you're done:









OK, now re-install the pistons in the cylinders. Lube the bore and the seal with brake fluid, align the pin in the hole in the back of the piston, and press the piston into the bore. Make sure the bleeder valve is loose to relieve any air trapped inside the back cylinder (I fought with mine until someone pointed out that I was fighting air pressure... duh). It won't go in all the way, so use a big C-clamp or a press. Keep the piston aligned evenly, you don't want it going in crooked! Press it all the way in, and then flip the larger seal over the lip on the outer edge of the bore, seat it in the groove, and install the supplied metal snap ring to secure it.

Here's a look at a correctly-rebuilt cylinder:



Do the inner and outer, and the end result looks like this:





Now, go clean up your caliper frame. I let mine soak in some Purple Power (I love that stuff).





I then cleaned the caliper frame with brake cleaner and painted it a contrasting color. Again, rust prevention and a clean, finished look.

Now, let's reinstall the cylinders on the caliper frame. Make sure you have the outer cylinder on the outer side of the caliper frame (use the other side as a reference). Also, you may have to rotate the piston in the cylinder - You want the flat part of the cylinder face (see picture below) perfectly at the bottom of the caliper frame, or it won't fit together - it will interfere with the caliper frame. It's a real snug fit, and make sure you're not pinching the outer seal (near the snap ring) as well.



I had already cleaned the 8 cylinder bolts, and you'll get new lock washers with the rebuild kit - Use them. I used a dab of anti-seize on each bolt. Here's what the finished product looks like:







Now, install new pads. For some reason, the pads I got were a tad too wide to slide down into the top of the caliper frame. That's why I have a bench grinder. I shaved the pads a little narrower. Any experts, feel free to tell me what I did wrong.

Put a dab of brake caliper grease on the back side of the pad, where the metal backing plate has a groove in it. This groove will slide down over the "nub" on the piston, which you can see in this picture:



You may have to tap the pad into place. Here's a picture of the completed caliper, loaded with fresh pads:



I then turned to the wheel hub. Remove the rotor by removing the cotter pin, castle nut, and washer from the spindle. Here's pic of the spindle before I cleaned it up.



And, after cleanup.



I then cleaned out the inside of the hub. Removed the bearings, cleaned out all the old grease, re-greased the hub and bearings, and reinstalled them. Before:



During:



After:





I used synthetic grease, and a butter knife is great for filling the inner hub:



Reinstall the caliper on the car (again, some anti-seize on the caliper bolts) and tighten everything up. Re-connect your brake lines and fill / bleed the brakes.

Here's some pics of it all finished:







I hope this was helpful. It's a long project, but when you consider it saved me about $700 over the cost of new cylinders, it's time well-spent. Now, Marilyn and I are gonna go for a drive.

excellent write up.

lemme give you a custom title!

Good write up Greg

A definite read for any DIYer. Great write up Greg.