Brake Master Cylinder Rebuild Seal Kit Service. This is an overview of a Nissan 300zx Z32 Brake Master Cylinder, that I rebuilt using an off the shelf seal kit from Kent Engineering. This same kit can be found at any reputable brake specialist store and workshop. This kit is universally usable on both Nabco and Tokico 15/16 Master Cylinders. The Master Cylinder in question is from a 1992, Naturally Aspirated, Non ABS 300zx. Master Cylinder Model number: BM-44 Bore size: 15/16 Manufacturer: Nabco Seal Kit Part Number: KPB2994X Tools Required. 10mm Spanner / Ratchet Spanner 10mm Tube Nut Spanner (not always necessary) 12mm Spanner / Ratchet Spanner 10mm Socket - (I used a 1/4? set) 12mm Socket - (I used a 1/4? set) 6? Socket Extension - (I used a 1/4? set) Socket Ratchet - (I used a 1/4? set) Medium Flat blade Screwdriver Small Flat blade Screwdriver 8mm Allen Key Small Flat blade File Ruler / Tape Measure Vice Grips / Large Adjustable Spanner / Bench mounted Vice Other Products Required. CRC Multipurpose Spray Electrical Parts Cleaner Degreaser PBR Rubber Grease Cleaning rags / Brush Seal Kit. Method. First off the mark, you have to remove the Brake Master Cylinder from the Brake Booster. This comprises of firstly removing the fluid from within the reservoir. Either using a rag to soak up what you can, or simply let it dribble out when you proceed to remove the cylinder. (NOTE: Brake fluid is corrosive to paint work ? if you spill any of it. Promptly wash it off with warm soapy water.) Next to remove are the 4 steel brake lines from the cylinder body. I used a 10mm spanner as the nuts were in good condition and came off rather easily. A proper tube nut spanner is preferred as they?re designed to grip onto the nut better, hence not destroying the nut should it be on nice and tight. Nothing worse than a rounded nut. Next there is a 2 wire electrical plug that needs to be unplugged from the base of the reservoir. This is the low level sensor wiring. (Theory behind this is: there is a float in the center of the reservoir that has a magnet at the base. Should the fluid level drop enough, the magnet will attract one pole onto the opposing pole within the reed switch, creating contact and activating the handbrake switch on your cluster.) Next there is a removable zip tie that keeps the wiring and vacuum hoses neat and tidily attached to the cylinder. Using the medium blade flat head screwdriver, remove the zip tie by lifting the little tongue and slide it out. Alternatively, get your side cutters and cut it out and bin it. Lastly there are 2x 12mm Nuts that affix the cylinder to the booster. With a 12mm spanner or ratchet spanner remove these 2 nuts. Hey presto, it?s loose. To completely remove the booster I had to remove the 2x M10 bolts that held the cruise control bracket/throttle cable bracket from the wheel arch to allow for some extra juggling room. You might not need to do this though. After removing the master cylinder from the vehicle, spray some degrease in and around the area. As no doubtingly you will have spilt some fluid in and around the area upon removal, along with the years of leakage. Don?t be surprised if you remove some paint when cleaning. Now the disassemble stage. First to attack is the reservoir tank. This is held into position by two seals that lock into a recess in the cylinder. Using the medium flat blade screw driver, carefully pry between the base of the tank and the seal and pivot against the cylinder body. With a bit of a wiggle one side should pop out, than the second. Should look something like this. And once the seals have been removed from the cylinder. Like this. Next you will notice at the rear of the cylinder a silver cap that has two tangs holding it in place. Using the small flat blade screw driver, pop out one of the tangs. Be sure to hold a little pressure against the cap otherwise it will spring away from you, due to the internal spring pressure forcing against it. Once removed, you will notice one of the two pistons poking out the end. Remove both pistons and put aside for cleaning and servicing. They should look like this. Next at the nose of the cylinder you will notice a small locking nut with an Allen key hole. This nut is fairly difficult to remove as it is a form of locking nut. First I got my small flat head screw driver and scribed a mark on the nut and cylinder so I would remember where to tighten it to upon reassembly. I than tightened the cylinder body into a vice as you will need a little leverage to remove the nut. Once in the vice, use the 8mm Allen key and proceed to remove it. Once again, you will notice one of the two valve bodies poking out. Looking like this. Remove the valve bodies one at a time, remembering there orientation and also marking them, 1 and 2. Than place them aside for cleaning and servicing. Now that the pistons, valve bodies and reservoir have been removed from the cylinder, give everything a good cleaning with degreaser. I had access to a kerosene bath. But whichever works best for you. Also remember to clean the terminals at the base of the reservoir with a small flat blade file. Once washed with degreaser I hit everything with electrical parts cleaner, to be certain that no contaminants were remaining on any parts. Once clean, take note of the bores of the cylinder. If there are any forms of pitting, gouging or scrapes. This rebuild will be of no benefit to you. Such damage will require the needs of a sleeve to be installed before you can continue with the replacement of seals. Failing to fix the bore, will result in a premature wear of the seal. Returning you to square one. Bore should look like this. Now to disassemble the pistons and valves of their seals. You will notice that the pistons have 2 larger seals. One is a cup seal, the other a wiper seal. Both external diameters are the same, but the inner diameters are different. Starting with the piston that sits furthermost into the cylinder. Pull the spring off. It?s only held on via a tightly would coil. After that a small washer will come off, than the seal. This seal has the smaller of the two inner diameters. To get the second seal off, use your small flat head screwdriver and pry under the seal to remove. Should look like this. Note this photo has the new and old seals showing. Using the PBR Rubber Grease, smear the new seals in grease along with the seats where the seals sit. Proceed to replace the seals in the reverse procedure that you used to remove them. Reattach the washer and spring. This is one piston completed. Place aside in a clean spot. Now the second piston. This one has a long bolt holding everything together, so for reassembly purposes, measure the total length of the spring in its compressed state. Keep this record somewhere safe. With one hand, compress the spring more than it already is, this will take some of the resistance off the thread of the bolt. While compressed, unscrew the bolt completely. Be sure to not let the spring go. It will launch away from you. Once the bolt has been removed you will see a cone type cup inserted into the spring, remove that. Remove than the spring and special washer, taking care to notice the orientation of the special washer. As it will need to go back together the same way it was removed. One side interlocks with the spring where the opposite side interlocks into the seal. Than with the same method as the first, remove the seals. Smear the new seals in the Rubber Grease along with the seats of the seals, and proceed to reassemble everything in the reverse order you removed them. You will have to compress the spring again in one hand to successfully reinstall the bolt, ideally to release the pressure against the threads and stop binding. Check the spring compression length against your recorded measurement. Once good, place it aside in a clean area. Should look like this. Note this photo has the new and old seals showing. Next to service are the valves. These are identical to each other the best I could see and only contain three small o-rings each. You will instantly see the wear on the old o-rings in comparison to the new o-rings. This tends to be a main contributing factor to the cylinder leaking fluid. Using the small flat head screwdriver, pry each o-ring off. Try not to gouge the seat as the metal is only soft. Once the old o-rings have been removed, smear the new o-rings in Rubber Grease, along with the seats, and reinstall them. Note: In the rebuild kit I received there were 5 o-rings that are identical in size to the old o-rings and one slightly thicker o-ring. I rang the supplier and they said it was either a mistake upon packaging or that in fact the thicker o-ring was there for a reason. They got me to check to confirm it will still fit into the bore at which it did. To our best guess, the larger o-ring is to be placed last in line (closest to the Allen key nut) so to add extra sealing force against the bore. Or at least it sounded half reasonable. Either way, this is what I did to mine and it has been working perfectly. If your kit doesn?t contain this slightly thicker o-ring, do not be concerned. Use what you have been given. The valves should look like this. Note this photo has the new and old seals showing. Now that the new o-rings have been installed onto the pistons and valves, its time to reinstall them into the cylinder. To aid the o-rings and seals sliding into the cleaned bores, I smeared a tiny amount of Rubber Grease into the bore. First up were the valves. Remembering their orientation and order number, slide them into the bore. If you have the larger o-ring like I did, you will need to give it a little extra love you make it slide in completely. Once installed, proceed to tighten the cylinder in the vice and retighten the Allen Key locking nut. Remembering to align the markings you make on the nut and cylinder. Next are the pistons. Again remembering the order in which they were removed, insert the first piston. Be aware to not fold the seals back on themselves, as this will cause all sorts of issues. The seals should slide in nicely providing you?ve smeared enough Rubber Grease onto them. Push the first piston all the way to the bottom. Then proceed with the second. Taking care with the seals. Now that the pistons are reinserted into the cylinder bore, you will need to get the cap and place it over the end of the cylinder. Holding it firmly in place with one hand and with the other, using the small flat head screw driver. Fold the tang back into position. This will now hold the pistons in position. Lastly we need to reinstall the reservoir. To do this easily. Prepare the new seals by smearing them in Rubber Grease, along with the seats on the reservoir. Slide the seats onto the reservoir and put aside for a moment. You will need to smear the cylinders seats in Rubber Grease also to make life easy for yourself. Once complete. Grip the tank in both hands (like you would if holding/picking up a bird) and place it over the cylinder. Remembering the orientation of the tank, you will need to have the electrical terminals facing the RHS of the cylinder. Then with you thumbs push like buggery until one seal inserts into the cylinders seat completely. Rotate the assembly and press again until the second seal is in position. That?s it! You have now completely torn down a Brake Master Cylinder. Removed and replaced the old seals with new. Reassembled. And have it ready for service once more. Providing everything went well, the Brake Master Cylinder should look like this. Now all you have to do is reinstall it onto the Brake Booster. Reattached all the brake lines, low level electrical wiring plug, fill the reservoir and finally bleed the braking system. Be sure to bleed all the air out of the brake lines prior to driving. All four brake lines will need bleeding! Thankyou for reading, hopefully this long write up will aid some people in another DIY job, saving you money and time. I can?t, however, stress enough though that this is a job than needs to be taken seriously. Any failure to repair the Master Cylinder successfully could lead to you not having any brakes under driving circumstances. If you feel you?re not comfortable in successfully doing this job. I highly recommend taking the vehicle or Master Cylinder to a reputable brake repair shop for servicing. Failure to do so is not only skimping out on your own safety, but also the safety of other road users. So I beg you, play it smart. Do only what your skills can achieve. Cheers. Sanouske.
Sorry about the crappy iphone pictures. And the rotation of the pics. Photobucket has been rather crap to deal with today. If i get the chance too ill rotate the pics to make it easier to see. Cheers.
Great write up! Pardon me if the answer is there as I didn't thoroughly finish reading but would this apply to TT's as well?
Great write up mate. The only things I would add is at the end, for pre 95 model ABS equiped cars, is that you ensure to bleed the ABS system. Also, while not strictly neccesary, I always like to bench bleed the MC itself after a rebuild, or if you putting in a new one. But, not strictly neccesary
Good one mate, it's great to see members take the trouble to share their findings with the rest of us :thumbup: The pics are fine, they get the point across quite well
Thanks mate. Realistically this writeup can be adapted for all brake master cylinders, zed related. Its just a matter of knowing what cylinder you have and than buying the appropriate seal kit to suit. The only other BMC i have seen has a screw/bolt in the side that has 2 tiny o-rings. From what ive gathered, this is a stopper. Its there to stop you putting the pistons through the other end when stomping on the pedal. Numbers 46070 and 46070A Thanks also. All very good points too. I never added it as ive never had to bleed an ABS system before. Didnt even really think about it. But a good reminder for others who are reading this. Cheers. The photos looked better on the screen when smaller, but got grainy when enlarged. Mainly the pictures of the cylinders bores i wanted clearer. But oh well. And lastly, thanks to everyone else who's posted a response. I thought if while i was at it, and hadn't noticed a write up regarding one before. I may as well take the time to do it. Just my 0.017 yen towards the forum.
