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Scary brake failure experience, any ideas why?

N

noisuf

Experienced Member
Joined
14 February 2012
Messages
362
Location
Melbourne, Aus
Hi Everyone,

Hope you all have a great and safe NY!

Went on a sprited drive today for a few hours in 35 degrees celcius / 95 degrees fahrenheit today.

Towards the end of a 2 hours stint, I thought I experienced brake fade for the first time. I checked the brake fluid levels and everything was ok.

We stopped off for a drink and bite before driving home.

On the way home, I had a very scary experience when going down a mountain run, the brake pedals sunk to the floor and I had to use the hand brake to slow down.

I limped home. It's a weird issue, when I pump the brake pedal, it's hard but if I keep pressing on the pedal, it will gradually go down to the floor. Like I'm bleeding brakes.

The fluid levels are still all good but can't help thinking I have a puncture somewhere in my brake lines? But if there was a puncture, wouldn''t the brake fluid levels be down?

Thanks for your thoughts and ideas. Hope I can get her back to being ok again.

Oh, I have standard brakes for a '93, no mods to the brake system.

Cheers.
 
Thanks for this. I've done some searching which points to some threads a few years back on where to buy one including some aftermarket ones.

I'll have a look at the dealer section but if anyone can point me to the right dealer to purchase one at a good price, it would be greatly appreciated.

Is the master brake cylinder the same between the LHD and RHD vehicles?

- - - Updated - - -

Hello again,

I've check with my local Honda dealer and they'll charge me $990 AUD to get it replaced including parts and a brake fluid flush.

However, I've just opened up the reservoir after cooling down a little and notice the fluid is noticeably darker than the brake fluid for the ABS. There's also what looks like dark 'chunks' at the bottom? Please refer to the photo.

I've read that sometimes changing the brake fluid helps?

9r6fxl.jpg
 
Sounds more like very old or contaminate brake fluid, I'd flush the system and inspect the brake lines,

Supercar is right on SS brake lines those can really make a nice upgrade whilst your at it.

Concerning the master cylinder, RHD is mirrored I recall, should have both LHD and RHD on the shelf I'll take a look after new years.
I should also have overhaul sets to repair worn masters.
 
100% it's a bad brake master cylinder. I've had this same thing happen to me multiple times. It's an easy DIY with a new OEM part.
 
Thanks everyone for your replies!!! I'm appreciative of your thoughts and advice.

I've had a good look for a master brake cyclinder DIY but can only really find brake flush DIYs and also debate over using original vs some aftermarket brands. I saw a 50/50 split in that OEM vs aftermarket debate. :)

If there are any DIY master brake cylinder change links that you can point me to, it would be greatly appreciated. My skill level is changing brake calipers, turbo back exhausts, rocker cover seals. Hopefully I'll be ok?

Cheers.
 
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Is engine off when you're pumping it? Does it go down the moment you start the engine?
You most likely boiled your brake fluid. I would start with bleeding your brake system using fresh juice. Brake master cylinders fail but it's less likely in this case.
 
Hi everyone, I have a new update along the lines of Solidol's thoughts...

When the car cooled down when I checked just now, the brake pedal did not slowly squeeze down to the floor. I then turned on the engine so the brake booster is on and tried again and it no longer depresses to the floor.

I'll bleed the fluid with new stuff and see how it goes.....it may be 23 year old fluid in there!!!??? It 'supposedly' had a brake flush 1 1/2 years ago at Honda but judging by the quality of the fluid in the reservoir, I have my reservations.

Still definitely have the master cylinder failure in my mind and will make sure I drive tentatively for a while after the fluid bleed.

Thanks Ian and Solidol for your extra thoughts. Appreciated.
 
I had the same thought about boiling the fluid as Solidol but looking at the debris in your fluid reservoir I personally would say that debris is from the master cylinder seals. It's your life, but I would personally change the master cylinder. Has it ever been changed on your car?
 
Happy New Year to all!
If the fluid was in there for 23 years it would be brown not yellow. The are tools which can measure the boiling point of the fluid. But you don't need that if you change it every two years (you should).
Old brake masters can/will fail like any hydraulic part (see clutch hydraulics). We will read quite a lot of threads about this regarding the amount of older cars. I saw some brake masters 'sweating' at the brake booster. It's not a bad idea to overservice the brakes and change parts before they fail. There's a reason why Japan has regulations on revising the brake system on a quite frequent base (every five years or so). Don't mess with the brakes as you don't want ot loose them when you really need them. Change the master and rubber lines and check for leakes at the calipers. For DIY: you have to bleed the system several times as a new master is at the beginning of the line and you still have air in the system after the first flush.
 
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It will get worse with new fluid. The seals have gone bad and they are letting the fluid go past and towards the booster. If you decide to drive the car give yourself a lot of room when coming to a slow stop. However, at high speeds if you quickly stab the brakes, you'll notice they bite well at first and then start to fade.
 
noisuf said:
Went on a sprited drive today for a few hours in 35 degrees celcius / 95 degrees fahrenheit today.

Towards the end of a 2 hours stint, I thought I experienced brake fade for the first time. We stopped off for a drink and bite before driving home.

On the way home, I had a very scary experience when going down a mountain run, the brake pedals sunk to the floor and I had to use the hand brake to slow down.

Oh, I have standard brakes for a '93, no mods to the brake system.

Cheers.
Click to expand...

I edited your post down to what I consider the salient points.

1) Ambient temperature was high.
2) You were on a "spirited" drive lasting two hours. I assume you were using the brakes pretty aggressively since said you experienced some fade.
3) Your brakes are OEM, not upgraded.
4) You experienced a near total failure downhill on a mountain.

Here's what I think happened: on your spirited run you got the brakes pretty darned hot. That accounts for the fade you first experienced, probably the pads getting overheated, especially if they are OEM or a "non-performance" street-only brake pad, i.e., not a street/track or track pad. Then you stopped for a while, allowing the heat from the rotors to saturate the calipers. At which point the fluid in the calipers boiled.

I'd start with a full flush and bleed. If it were my car, I'd ALSO change the master, because it is also as equally possible the seals in the master are giving up. It could also be a situation where, while coincidental, BOTH the master cylinder is giving up the ghost, AND the fluid in the calipers had boiled. In fact, I'd change the master, (reference to a brake slave cylinder deleted - DJQ), and give it a good bleed. I might even consider rebuilding the calipers since from what I understand, after boiling the fluid, the caliper seals then become suspect.

But if I had to go easy on the investment (time and money), I'd do the master, and bleed, oh, and flush and re-fill using a performance fluid, like Motul 600 or ATE, especially if I plan to drive in a spirited manner again.
 
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The procedure for replacement of the master cylinder is set out in the service manual. If you don't have a service manual you should get one by purchasing a paper copy or go to the various links in the NSX Prime wiki to find .pdf versions of the manual. Unfortunately, I expect that they are all for LHD cars. The NSX GB site might have versions for RHD cars. You need a service manual as you have a 23 year old car and you will find that when you go to the dealership for servicing, the chance of finding a mechanic who has seen an NSX let alone worked on an NSX will become increasing rare.

The process of replacing the master cylinder is not overly complicated, although can be a bit awkward. Read over the section in the service manual and if you are uncomfortable with the procedure, take it to the dealership. They may not have done an NSX before; but, at least they should know the procedure and have the correct tools.

You said that the brake system was flushed 1 1/2 years ago. I have discovered that in 'Dealership speak' sometimes flush just means replace in which case they vac out the master cylinder reservoir and replace with new. Looks good and what you can't see can't hurt you- right? The fluid in the lines and calipers does not get changed. Aside from the mystery bits of stuff floating around in the MC, your brake fluid looks relatively fresh. Old fluid tends to look murky brown. If you had a fluid replace rather than flush, you could still have old fluid in the calipers. Brake fluid is hygroscopic and will accumulate moisture. Normally the moisture stays in suspension; however, it does suppress the fluid boiling point. If you got your brakes really stinking hot, you might have flash boiled the fluid or if the water had come out of suspension in the caliper, it could have boiled which would occur at a much lower temperature. This might explain the brakes returning to semi normal after a cool down.

You could try flushing and bleeding the brake system to see if contaminated brake fluid is the source of the problem. I would recommend pressure bleeding rather than the more conventional pump the pedal bleeding process. Pump the pedal to the floor on a 23 year old master cylinder and you will likely destroy the piston seals. As a further observation, if when you incurred the brake fade problem the brake pedal went to the floor and you repeated that attempting to get the brakes to work, you likely damaged the master cylinder piston seals, even if the original problem was unrelated to the master cylinder. After normal use of the brakes on older cars, the bore of the MC wears over its normal travel range leaving a ridge at the end of that travel range. If / when the pedal goes to the floor the piston goes past that ridge. Sometimes the piston seals will survive going past that ridge, sometimes not and they will fail immediately or operate with reduced efficiency after that.

As I said, you can try the flush; however, since you are someone who seems to use your brakes vigorously, I would be inclined to replace the MC since you likely impaired or damaged it when the pedal went to the floor during your brake failure event. The fact that after cool down the pedal still slowly sinks to the floor suggests that the MC is impaired and should be sent to the garbage bin.
 
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I would not drive the car AT ALL before the car is fixed by capable hands. Brakes fail when you urgently need them. Adding to NSXGB: it's not only your life, you're endangering other people on the road too and a serious failure on a spirited drive might not end but certainly ruins one's life (at least financially). I'm no teacher but understand my proposal as a good intention for New Year. :)

You don't have to do what I did but it might serves as a benchmark. From 2008-2012 I've overhauled the complete brake system on my 91: new master, new OEM rubber brake lines, new ABS, overhauled calipers. Brake fluid changes every spring with normal DOT4. Even a light front-impact will cost more than servicing the Brakes for the next 100 years.

Slave: there is no slave in the brakes but I think it refers to the clutch hydraulics.
 
NSXGB said:
Slave?
Click to expand...

This is me on auto-pilot not thinking about what I am typing. Of course there is no slave in the brake system. Temporary insanity on my part. Please excuse my error. And I didn't even drink last night to ring in the New Year. Duh.
 
Wow!!! A big thanks to everyone for your thoughts. There's a lot of great advice and yep, I've been looking for a master cylinder to change as I've been given sage advice the black stuff look like seal material.

I'll try to change the master cylinder myself to avoid a catastrophe on the way to the dealership. There's a dealership in Melbourne that has always worked on NSXs who has quoted the $990 AUD to supply and install but it's around 20 miles away.

Are the LHD and RHD master brake cyclinders the same? It looks like a OEM one would set me back around $300USD not including postage. Is there an aftermarket one that can be 'trusted'? :)

Changed the master and slave clutch cylinders 1 1/2 years ago including ALB hose.
 
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If you do the bleeding procedure yourself I'll recommend a vaccum bleeder tool like this: http://www.ebay.com/itm/Brake-Fluid...:g:~14AAOSwv-NWbkKM&item=371508223231&vxp=mtr Speed bleeders for example don't work with air in the master. You need to do at least three stages until the smallest bubbles of air are out of the system. After stage one the brake pedal still feels long and soft. To exercise the brakes several times during vaccuum bleeding helps to get wrid of the air bubbles faster.
 

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