Brake problem. Advice needed.

[AshL]

Hi guys,

I'll try make this as short as possible.

I went to ADI and did 3 track sessions.
During this my brake pedal went long and spongey and has stayed like it.
I've had my brake fluid changed 2 days ago but this hasn't helped restore the pedal feel at all.
The garage I took it to said I may need a new brake master cylinder.

What are the chances that I do in fact need a new one and are these known to fail? Is there anything else that could be at fault?

Any other info on the matter would also be much appreciated.

Thanks in advance,

Ash

 

[<tuffty/>]

Did you bleed the master cylinder as well as the calipers?

<tuffty/>

 

[gokiwi64]

ABS pump maybe ?, have the pads been changed ?

 

[SamHendry]

Mine failed on me. Brake pedal rather than go solid with pressure, it would slowly sink to the floor, brakes would still work but you had to pump the pedal. It's a real pig to change.

 

[desertstorm]

As above suggested by Tuffty, I didn't know there were bleed nipples on the master cylinder as well. Always had a slightly spongy pedal until I bled the two nipples on the master cylinder and it's solid now. The bleed nipples are very small so don't get carried away with tightening them as they would be very easy to snap off.

 

[AshL]

Did you bleed the master cylinder as well as the calipers?
<tuffty/>

I took it to a garage, the guy said he bled it from the calipers, I shall ring them and ask if they bled the master cylinder also.

ABS pump maybe ?, have the pads been changed ?

If it is the ABS pump would that need to be replaced or bled? Regarding brake pads I haven't had them changed no.

Mine failed on me. Brake pedal rather than go solid with pressure, it would slowly sink to the floor, brakes would still work but you had to pump the pedal. It's a real pig to change.

Did what you are describing happen when the engine was on or off?

I just went out to the car:

With my engine off my brake pedal will go solid as I pump it and I don't won't go to the floor.

When I turn the engine on the pedal is then able to be depressed. The pedal of course is soft and has a longer travel than before, but I held it down and it wouldn't go to the floor (engine on).

Maybe that will help you understand more what's going on with mine?

As above suggested by Tuffty, I didn't know there were bleed nipples on the master cylinder as well. Always had a slightly spongy pedal until I bled the two nipples on the master cylinder and it's solid now. The bleed nipples are very small so don't get carried away with tightening them as they would be very easy to snap off.

Ah ok I will find out if it was bled and go from there.

-------

Are the bleed nipples on the MC easy to see/access? Maybe there's a picture somewhere?

I really appreciate all the help and advice guys!

Cheers,

Ash

 

[desertstorm]

If you look on the passenger side of the master cylinder under the brake fluid reservoir you will see the bleed nipples.

 

[Retroman]

I've known road brake pads overheat and delaminate during track sessions - the piston taking up the resulting gap causing long brake pedal travel

 

[AshL]

If you look on the passenger side of the master cylinder under the brake fluid reservoir you will see the bleed nipples.

Thank you for that much appreciated!

I've known road brake pads overheat and delaminate during track sessions - the piston taking up the resulting gap causing long brake pedal travel

I just did a quick search on what delamination of the brake pad is as I didn't know this could occur. Is there anything to look out for while driving that could point this out. Of course getting the pad off would be the best way to check but I can't do that until later.

I've also noticed quite a few times that when I brake to a stop and then release some of the pressure from the brake pedal I hear a clunking sound. It isn't really loud but it's enough to clearly be heard.

Any thoughts on what that might be?

Again, thank you for the help.

 

[SamHendry]

I took it to a garage, the guy said he bled it from the calipers, I shall ring them and ask if they bled the master cylinder also.



If it is the ABS pump would that need to be replaced or bled? Regarding brake pads I haven't had them changed no.



Did what you are describing happen when the engine was on or off?

I just went out to the car:

With my engine off my brake pedal will go solid as I pump it and I don't won't go to the floor.

When I turn the engine on the pedal is then able to be depressed. The pedal of course is soft and has a longer travel than before, but I held it down and it wouldn't go to the floor (engine on).

Maybe that will help you understand more what's going on with mine?



Ah ok I will find out if it was bled and go from there.

-------

Are the bleed nipples on the MC easy to see/access? Maybe there's a picture somewhere?

I really appreciate all the help and advice guys!

Cheers,

Ash

Was it like this before ADI?

I accidentally snapped the bleed nipple off my old MC which meant I couldnt fully bleed the system and the pedal I was getting sounds like what your describing, long and spongy.

 

[AshL]

Was it like this before ADI?

I accidentally snapped the bleed nipple off my old MC which meant I couldnt fully bleed the system and the pedal I was getting sounds like what your describing, long and spongy.

Before ADI my pedal was fine. I think I noticed it during my second session, although I thought it was just because they were getting hot and fading a little. I'll know to keep an eye out for it in the future.

 

[Retroman]

The pads in question were - wait for it - EBC Red Stuff fitted to the front of a BMW M car. The friction material on one front pad just disintegrated and collapsed - after one spirited session. We're all just throwing guesses on a forum without being on the spot, but no harm in having a closer check of the pads - I would focus on the front. I would suggest taking them out and having a close inspection - they can crack and crumble under extreme conditions and heat.

 

[AshL]

The pads in question were - wait for it - EBC Red Stuff fitted to the front of a BMW M car. The friction material on one front pad just disintegrated and collapsed - after one spirited session. We're all just throwing guesses on a forum without being on the spot, but no harm in having a closer check of the pads - I would focus on the front. I would suggest taking them out and having a close inspection - they can crack and crumble under extreme conditions and heat.

I'm guessing that you don't recommend EBC brakes? Ha.

Yeah definitely I understand it may or may not be what you are suggesting but as you say it's better to check the small things first before forking out the money.

I'm going to check them tomorrow to see how they are. I've never jacked the car up without the crappy jack in the spare wheel. What points can I safely jack it up with a proper jack? I don't really want to put a hole through the floor.

Cheers.

 

[Retroman]

My 8p has little arrow marks impressed into the sills which you can just see through the stone-chip paint covering. Those are the strengthened jacking points. I would guess that your car is similar - I know the VAG range generally has similar.

 

[AshL]

UPDATE: PROBLEM FIXED

On the recommendation from @Retroman to check my pads for delamination I found one front pad was severely worn close to the metal. The other pads were unevenly worn in their respective pairs and when comparing left wheel to right wheel. Maybe the previous owner didn't change in pairs?

I purchased new pads for all wheels, changed them and the pedal is now even better than I remember in terms of firmness.

What do you guys think would be the reason for this curing the spongey pedal?

Cheers.

 

[<tuffty/>]

What do you guys think would be the reason for this curing the spongey pedal?

Not running out of travel on the pedal with no pad material

<tuffty/>

 

[Retroman]

The problem with normal cars and occasional track use is that the cars are at their full weight (not lightened) and often there is insufficient directional air cooling for the brakes. Furthermore, normal road pads can actually crack & crumble because of the heat and cheap, standard Dot 4 brake fluid can also loose it's effectiveness because of heat. Popular pads for first stage, occasional track use on road cars are Ferrodo DS2500 and EBC Yellowstuff although I would suggest doing your own research as I don't claim to be up-to-date. Anyway, glad you got it sorted

 

[hydro s3]

What would be the best brake fuild to use if dot 4 is not?

 

[Retroman]

People who track cars get concerned about the "boiling temperatures" of brake fluid caused by extreme heat on braking at high speeds on a track.
Audi standard DOT 4 = 172 C (wet boiling)
I use Castrol React Performance DOT 4 = 190C (relatively inexpensive)
Some people insist on changing to DOT 5.1 (not to be confused with DOT 5) but many racing DOT 4s have higher boiling temperature, the DOT 5.1 label being more of a technical rating relating to viscosity at certain temperatures.
For example Castrol SRF React DOT 4 = 270C (expensive)

Important to remember that brake fluid should be clean and fresh as it will lose its effectiveness with age.

In many cases DOT 5 cannot be mixed with other fluids and may be unsuitable for conventional braking (and braking assist/stability) systems

 

[gokiwi64]

Also would recommend checking and replacing the flex lines as they degrade over time too.

 

[hydro s3]

Thank you that was so well explained.

 

[AshL]

Thanks to all you guys for the help! It's much appreciated.

Cheers,

Ash.