Spongy brake pedal

[Classik]

For lack of a better word, the brake pedal doesn't feel as firm as I think it should be.

Full story is that it started like 2 months ago with a standard maintenance brake fluid change and brake hose replacement on all 4 wheels with those HEL hoses: https://www.ultraperformance.fr/durites ... nte=333845 . 10 days later I had a brake warning on the dashboard that was easily cured by filling a few cc of brake fluid into the system, then I forgot about the whole thing, thinking some fluid was missing due to the recent intervention. Fast forward 1 month later for the MOT that failed due to a leaking rear calliper, which obviously explained the above brake warning..

As of now I've changed both rear callipers (for TRW ones) and made a brake fluid bleed on all 4 wheels (didn't get much air), then did a 400 meters trip (yes 400 meters due to the confinement..) to check everything's fine. Good new is that there's no more leak, but as the title says I'm not happy at all with the feeling on the pedal (despite numerous pumping) and I don't get a firm bite & grip as good as I think it was.

In your opinion, would you say the car needs to run for more than a few hundreds meters for things be back to normal, or is there something else to worry about, like the master cylinder or the brake servo. FWIW visual inspection on both the master cylinder of the servo didn't show any sign of wear or corrosion. Or maybe those HEL hoses are not as good as they should?

[Shoppinit]

If you maintain pressure on the brake pedal when stationary with the engine running, does the pedal slowly sink?

[Classik]

If you maintain pressure on the brake pedal when stationary with the engine running, does the pedal slowly sink?

Well it doesn't go down to the floor as when I had a leak, but it's not clear cut. When I hit the pedal there's a first point of resistance, but then it very slowly sinks to a second point where it would stop for good, like 15cm from the floor. No scientific measurements, but the first point of resistance mentioned just above is where the pedal would stop before it all began.

[Shoppinit]

Sounds like you’ve still got air in there. How did you bleed? And did you purge?

If your level went down too much you might have some air in there drawn in through the reservoir. It’ll be a pain to get out. You’ll need to purge with lots of fluid.

When I purge I buy lots of cheap ECP type fluid (cos it’s gonna go in the bin) then when I’m sure it’s all been purged I put the good stuf in.

This used to be much easier when you could get ATE super blue.

[Classik]

I did [edit] bleed with the usual Gunson Eezybleed... But I wasn't aware I need lots of fluid.My understanding was that you let the first bubles of air go out then when you get a continuous leak of fluid, you're done.
Started Front left, front Right, Rear Left, Rear Right, to push the air from the reservoir to the most farthest wheel.

[Classik]

Full purge was done 2 months ago, so the fluid is clear & clean as new (which it is).

[Classik]

So to summarize I want to purge the circuit with as much fluid as I can afford. Shall I do it through the front left, or at the contrary through the rear right?

[Shoppinit]

Full purge was done 2 months ago, so the fluid is clear & clean as new (which it is).

Was this before or after the low fluid alarm?

[Classik]

Purge was done by the mechanic like 10 days before the fluid alarm.

[Mɐʇʇ]

I've upgraded from Gunson easibleed to this, which I ran at 30-35PSI. I am completely won over, it's good, having used easibleeds for 20+ years.

Previously my brake pedal was just a little too spongy (done by garage and then I asked them to do it again), so this time I did it myself.
Like Shopp, I do tend to put a fair bit of fluid through, especially when starting from scratch.
I also cycled the ABS unit (not necessary officially, but I could so I did) via VCDS.

The only issue now is with new calipers, master cylinder discs and pads all round, the pedal is super light and super responsive - by far the best it's ever been.

[Shoppinit]

I’m going to get one based on your recommendation.

[Shoppinit]

My point was that if you sucked some air in through the reservoir then you’re going to have to put a lot of fluid through the system to get the air out. You confirmed that the purge was before this event so there could be air in there.

[Mɐʇʇ]

In my case, my system was empty. Between getting fluid through and no bubbles at all was a surprising amount - including multiple circuits of the system

(Which I think backs up Ben’s point)

[Classik]

Thank you all for the follow up.
Just tried again a few minutes ago : now the pedal goes all the way through to the floor : Furthermore there's a fluid leak at the same wheel that caused me troubles in the first place, which is strange as the calliper has been changed.
Too late for further investigation as we speak, but I start to wonder if there could be something fishy with this HEL brake hose (banjo connector?), more later..

[Nobby]

Your not missing a copper washer on the banjo bolt or anything? I.e there needs to be 2 - one on each side