Brake issue

[richard_au]

Ok, firstly let me start by saying that I have searched and read almost every post on the NSX brakes.

Since some upgrades to my car the brakes have been playing up a little.
Basically after driving the car for some time or driving in hot weather the brake pedal becomes soft to press and to stop the car the pedal needs to be pressed all the way to the floor. After reading multiple threads on here I decided it was either air in the lines or the master cylinder.
So I took the car to a mechanic and they bleed the brakes. The pedal feel when the car is cold is amazing, super strong and you just need to apply a bit of pressure to the pedal. However, again after driving in traffic for a bit the pedal starting getting spongy and then went all the way to the floor.
So I then ordered a new master cylinder and some speed bleeders and took it to the mechanics. He seems to think there is nothing wrong with my master cylinder and the problem is actually the abs.

He said something about the master cylinder holding pressure (not sure how this was tested) and that my abs needs to be replaced.

After extensive searching on here, I am lead to believe that an abs failure or issue would not lead to a soft pedal feel.

So anybody got any ideas on how I can determine if my problem is the master cylinder or the abs.

I think I will just replace the master cylinder and go from there but any suggestions would be appreciated.

I have a 91 NA1 NSX

 

[sharkwerks]

Ok, firstly let me start by saying that I have searched and read almost every post on the NSX brakes.

Since some upgrades to my car the brakes have been playing up a little.
Basically after driving the car for some time or driving in hot weather the brake pedal becomes soft to press and to stop the car the pedal needs to be pressed all the way to the floor. After reading multiple threads on here I decided it was either air in the lines or the master cylinder.
So I took the car to a mechanic and they bleed the brakes. The pedal feel when the car is cold is amazing, super strong and you just need to apply a bit of pressure to the pedal. However, again after driving in traffic for a bit the pedal starting getting spongy and then went all the way to the floor.
So I then ordered a new master cylinder and some speed bleeders and took it to the mechanics. He seems to think there is nothing wrong with my master cylinder and the problem is actually the abs.

He said something about the master cylinder holding pressure (not sure how this was tested) and that my abs needs to be replaced.

After extensive searching on here, I am lead to believe that an abs failure or issue would not lead to a soft pedal feel.

So anybody got any ideas on how I can determine if my problem is the master cylinder or the abs.

I think I will just replace the master cylinder and go from there but any suggestions would be appreciated.

I have a 91 NA1 NSX

If the pedal is acting inconsistently like that and not the same it really does point at the master cylinder failing.

I'm changing mine out along with upgraded rotors, pads and lines soon too.

 

[pgilliam1]

It sounds like the master cylinder, however I have never heard of heat affecting it (it's either leaking, internally/externally, or not - hot or cold).

I'm assuming your fluids in both the master and ABS reserviors are staying level and there are no leaks anywhere. There are simple tests for the check valve and brake booster that you should try (the WIKI details them).

Good Luck and be sure to post your solution :wink:.

 

[DocL]

As already mentioned it's the master cylinder. I had intermittent problems with my pedal a few years ago just like you. It's an easy DIY.

 

[nsx_2k]

I believe it is the master cylinder failing. The symptoms you describe of the brakes feeling firm when cold and then becoming soft/spongy as the vehicle warms up is a classic sign of master cylinder failure.

 

[nsxnut]

It is you master.

Don't bother with the speed bleeders. I have these on my car and they don't work well at all.

 

[LJZ]

+1 exact symptoms had with my /94 @ 30,000 miles -- mas cylinder replacement cured the problem. And yes, I for sure noticed the sinking feeling in warmer weather as opposed to cold for some reason.

Best,
Jeff

 

[A.S. Motorsport]

Indeed sounds like your master cylinder,
Is your brake fluid level still the same after this issue happens?

 

[richard_au]

So I have changed the master cylinder and pressure bleed the brakes. Is holding well for now so hopefully that will fix it.

Have not been for a super long drive yet so time will tell.

If it keeps happening it could be the new exhaust/headers heating up the brake fluid, though i would find that hard to believe

Thanks all for your help

will keep you posted

 

[Oldduffer]

I'm thinking I need to change my master cylinder too. My question is, do I get it from an Acura dealer, or some aftermarket brand? Howard

 

[pgilliam1]

I'm thinking I need to change my master cylinder too. My question is, do I get it from an Acura dealer, or some aftermarket brand? Howard

Any new or rebuilt unit will work fine. I replaced mine with a rebuilt unit off of eBay from a reputable seller 2 years ago with zero issues and I track my car.

 

[nsxnut]

So I have changed the master cylinder and pressure bleed the brakes. Is holding well for now so hopefully that will fix it.

Have not been for a super long drive yet so time will tell.

If it keeps happening it could be the new exhaust/headers heating up the brake fluid, though i would find that hard to believe

Thanks all for your help

will keep you posted

Brake lines don't go near the headers or exhaust.

My bet is it was the master.