NSX Health Check Service

[Kaz-kzukNA1]

2. Brake Master Cylinder
For the same reason above, in the past, it was mandatory to OH the brake master cyl (MC) regularly in Japan.
In UK and US, the workshop manual only tells to replace the entire brake MC as an assembly and there are no overhaul procedures.

Eventually, we’ll struggle to source the parts in the long term future so personally, I think it is best to know how to refurbish the existing parts rather than just simply replacing them.

Because of the price of the parts and the fact that it should be replaced as an assembly, it seems that many owners are running their NSX with aged brake MC or even with tiny leakage without being noticed.

It is recommended to OH the brake MC at least every 3 years or at the time of calliper OH.
While I was in Japan, it was very rare to see any sign of leakage or rust at the base of brake MC on NSX which was caused by the old leakge.

In UK, most of the NSX that I saw during the Health Check Service or during certain events showed sign of old leakage.

I would strongly recommend to have your brake callipers and MC overhauled on a regular basis regardless of your annual mileage.

Below the brake fluid reservoir, there is a brake master cylinder (MC). It is connected to the brake vacuum booster system which is black colour metal with round shape object at the front bulkhead.

Quite often on many NSX, I saw sign of leakage or trace of old leakage at the base of MC, i.e., the rust mark caused by the brake fluid at the black metal cover of booster system. You can see the trace of leakage around the stud bolt on the left part of the photo.


For some reason, it is not serviced regularly in UK. In fact, the English version of workshop manual states to replace the entire MC assy rather than to overhaul it. Probably something to do with the local regulation and to avoid complex issues caused by the human error.

The entire assys costs about GBP575.00 inc.VAT + labour so probably this is one of the reasons why it was not treated as regular maintenance item…

As long as there is no scratch/damage to the internal bore of MC, you can overhaul it and save a lot even including the labour charge.

As it is part of the brake system, I don’t think it is a good idea to wait until it starts to leak and then carry out the service.

The procedure is quite simple as it is similar to other cars. After disassembling the MC, clean it and inspect it carefully.
Then, use the overhaul kits to re-assemble.
Although I have never come across to the NSX that required the adjustment of the pushrod clearance at the brake booster, I always check it using the special tool as I don’t know the full service history of each NSX.

This is very important as you are either having too much play before the brake pressure rises or continuously applying small brake pressure which will be very dangerous.

Once everything is checked, the nice shiny overhauled MC is back in place.


Although it is not necessary, it may make your life easier if you bench bleed the MC prior to fitting it back on your NSX. If you consider the hydraulic line of entire brake system, you are going to take long hours to bleed the system without bench bleeding the MC first. This is the same even you use gravity bleed or other methods.