Hey boys....


hoping for a bit of advice... and fingers crossed for a quick fix.
had my car out for a tune a few weeks ago.
was driving perfectly fine when i put her back in the garage.
she's been sitting there since.

grabbed her out yesterday, and wasn't feeling any brake pressure on the pedal.
went for a good drive and things didn't improve.
im getting no pressure feeling when i turn on the car either.

basically, i get no brakes what so ever until i push down about 3/4 of the pedal range.
even then, they are weak and its borderline not drivable.

quick check in engine bay and behind all wheels shows no signs of any leaks.
brake fluid flush, braided lines and all pads and rotors were installed at a workshop less than 10k ago... so should be good...

am i looking at a brake booster issue or something of the sort?
i know my way around my FD in general... but the brakes I've never had an issue with...


any advice would be much appreciated!



thanks in advance 😊


Merlyn

 

If the pedal feels soft and the brakes feel ineffective, then there are two common possibilities:

1) There is air in the brakes. Bleeding should fix this.

2) The master cylinder is failing and needs to be replaced.

It can't be the booster, the booster would result in a very hard pedal.

Vince

 

thanks for the input Vince!

yes, the pedal does feel soft... no pressure and will only brake when it is depressed very low.

pleas excuse the novice question, but how could it be working fine when i park it one day, and then a few weeks later it just has air in there?
there are no visual leaks.... etc.

one thing to note is that the hose connecting to the UIM from the master cylinder is looking extremely 'tired' and in need of replacement.
this has been on my list to do ironically in the last few months.
been doing more research, and i believe this line has a check valve moulded into it...

some people have mentioned similar issues with the problems being that valve had failed.

could this be the cause??



thanks in advance 😊



M

 

This ^
Reread it again.



My brake master was faulty and exhibited this exact thing. Well actually it was the check valve in the brake master got trash under it causing it to bypass internally. They do not make a new OEM brake master. But they do make a rebuild. Mushy brakes is either air or bypassing.

~GW


Edit ~ just realized your location. Right hand guys may be able to get a new one.

 

thanks guys... appreciate the input 😊

 

Does your reservoir appear low on fluid? It could be your slave cylinder for the clutch. It will sometimes drain into the transmission bell housing so you won’t see a fluid leak.

 

Yeah make sure you're not bleeding fluid. Maybe they just forgot to shut one of the ball valves on the caliper.

 

quick update....

did another full inspection today and some tests.
there are no leaks i can see whatsoever.
depressed the pedal before startup and turned engine on.
felt the pressure change and pedal move.
as mentioned, they were fully bled and everything (rotors, callipers, pads) changed a couple of years ago and barely done 2000 miles.
it was running beautifully up until last week.

so weirdly... took it for another test drive and brakes are working fine!
very strange.


glad its working, but obviously don't want anything to fail while driving one day... so am keen to figure out what the problem is.
could it have just been a bit of air working through the system and got its way out?
could it be the check valve in the hose to the UIM playing up?

fluids are at perfect levels and all seems good.


only other thing to note, and im not sure if this is related at all whatsoever....
but usually when i leave the car sitting for a month or longer... the clutch will need a minute of pumping to get going.
i've heard this is normal, but thought i would mention in the off case that they could be related.


thanks again for all the input!!
much appreciated 😊



Merlyn

 

Could air have worked it's way out of the system? Nope.

Could it be your booster hose check valve acting up? Probably not, because that would result in a hard/high pedal. But I would still test it.

Your master probably has a bad/dirty internal check valve or sticky plunger as stated. I would replace the master so you don't have to sweat it. Brake failures can be fatal to you or someone else. Why screw around?

Sounds like you need new clutch hydraulics as well. I'd just go ahead and do the master/line/slave.

Regarding the statement that a bad booster can only result in a hard pedal... I had a crazy brake problem in my FC way back. It had a spongy and low pedal that had a very sensitive initial response, but would not let you lock up the brakes no matter how hard you tried. I replaced EVERY SINGLE HYDRAULIC COMPONENT of the brake system to the point that I had a Wilwood proportioning valve, new lines, stainless hoses, new calipers, new MC... everything. I even took the car to a shop that had caliper pressure gauges to try and diagnose it. The very last thing I replaced was the booster and that solved the problem. Not saying it's your problem - just saying booster issues are not always so cut and dry.

 

definitely sounds like a master cylinder to me

 

thanks for the input Gracer and Alex!!

definitely want to get it sorted... so will look into a new master cylinder 😊
was reading somewhere they can't be purchased new need rebuilding?

is this the case?
not sure on the aftermarket options...


just reading on Banzai website the 929 master cylinder is a common upgrade to the FD one... true??

 

If I were getting a new MC it would be a 929.

You get a little stiffer pedal, a little less throw, but you need to press it slightly harder.

The chips motorsports 929 MC is a bolt in replacement. Otherwise you have to fiddle with bending a new line.

 

The 929 MC is a good upgrade, especially if you've got to replace your current MC anyways. That was my situation as well. I've still got the stock brakes but it opens up the path to easily upgrade to a bigger brake setup in the future. I ended up getting pre-flared brake line from autozone and bending it myself. It's really not too difficult to do so if you're patient with it.

 

As the others have stated, it's very likely the internal valve in the master cylinder is causing it to bypass. The easy way to confirm this is to look in the matter cylinder while someone else presses the pedal down. If you see a fountain of fluid in the reservoir, that's the bypassed fluid going back into the reservoir instead of out to the calipers.

The reason it seems to be coming and going is this: NO ONE ever flushes the brake fluid with any regularity and weird stuff happens with old fluid.

Either rebuild or replace the master cylinder and you should be good.

Vince

 

really appreciate all the input boys 😊
i'll try that test Project88...
do i need the cover off to be able to see this?

i have already done a brake upgrade to the larger spiritR callipers with braided lines all round.
can't see myself upgrading in the future... they feel plenty enough for me 😊


also... im in Australia... so its a RHD.
not sure if the piping is different for an upgraded MC... but i'll look into it 👍

 

twas the master cylinder...
bleed didn't change anything unfortunately.

upgraded to the improved 929 from chips motorsports.
nice pedal feel, and should be a solid upgrade for the long term...

 

has anyone found a replacement brake booster that works? I got recommended the 2003 Protege, or the 1995 929 with ABS, '90s Subaru Legacy, but I prefer to get a good used stock one before I venture out to try and make another work. Anyone know more? Thanks

 

Not that I know of. But, the stock booster works well and rarely fails, and are fairly plentiful used.

Dale