Spongy brakes

[ChrisHC]

The brakes of my E30 have a horrible spongy feel to them, although they do stop the car. Changing the fluid, replacing the hoses to Aeroquip and bleeding have not helped much, so I am thinking about replacing the servo. Wiki advises using one from a Renault Clio, any car from 2001 on, but there appear to be different servos used on different Clio models, and there are both 9 inch and 10 inch ones at least. Can anyone be more specific, or does it really not matter? Is it best to fork out for a new one or will a used one in good condition be perfectly fine?

[Cloggy Saint]

The clio servo is only really used when doing an M50/52 conversion as the E30 servo is too big to fit alongside these larger engines. I'm not sure there's any benefit to fitting one if you still have an original E30 engine but I could be wrong.

[jmc330i]

As above, the Clio servo is used to free up space to allow non standard engines to be fitted, but a Clio servo will be newer than any E30 servo...
I was always told the 2001 plastic wing Clio is the one, I didn't realise there maybe different sizes but I'd think the 9" is what people use for the conversions.

Not sure a faulty servo will cause spongy brakes though. That will more likely be down to the hydraulic side of things and as you've changed the hoses and bled them (if you're sure you've got all the air out), I'd be looking at the master cylinder.

I had horrid feeling brakes on an E30 I bought recently, but that was down to cheap pads and discs that had been left unchanged for far, far too long so were well below the minimum thickness!

[ChrisHC]

It was DanThe's suggestion that the cause might be the servo and the cure to fit one from a Clio. Other ideas are welcome!

[paultv]

if you have new fluid and soft lines it sounds like master cylinder, assuming your discs are good and pads are new, decent quality. I fitted a 750 mc 25mm unit, great results, firm responsive pedal, but this only after actively bleeding the ABS pump which has been a constant pain since replacing hard lines and callipers.

Did you do a simple servo pedal test?

Paul

[DanThe]

Hi Chris, I was blaming the servo for the lack of pedal assistance, funnily enough I had another zoners car with a similar poor pedal a couple of weeks ago, nothing really happens until you have your full weight on the pedal

[reggid]

dodgey servo gives hard pedal, mushy could be MC

[ChrisHC]

Ah, I misunderstood. So the way forward might be:
1. actively bleed the ABS pump. How is that done?
2. if that does not fix it, replace the master cylinder or possibly the master cylinder and servo together?

[Carmo13]

if you have new fluid and soft lines it sounds like master cylinder, assuming your discs are good and pads are new, decent quality. I fitted a 750 mc 25mm unit, great results, firm responsive pedal, but this only after actively bleeding the ABS pump which has been a constant pain since replacing hard lines and callipers.

Did you do a simple servo pedal test?

Paul

How does the mc you fitted differ from a standard unit?

[paultv]

it' a direct swap, but has a larger bore - 25mm rather than 22 - it pushes more fluid for less travel and gives a better pedal - doesn't actually improve the brakes, but the feel is great - its for a BMW E32 7 series - I'm sure its a listed mod on the wiki here.

Paul

[Carmo13]

Nice one, i will be looking into it.

[DanThe]

It just means you have to press the pedal harder to get the brakes to work, not my idea of a good mod but each to their own

[jmc330i]

The 25mm master cylinder swap is an apparent upgrade for the M3. I've run a 25mm m/c on mine with both 325i and M3 brakes and as Dan suggests, I didn't enjoy it with the 325i brakes.

[paultv]

What I found with the 22mm was the length of pedal travel before the brakes bit - maybe that was down to the MC, but whenever I hit the brakes I was a bit freaked by the delay - I like the instant feel of the 25mm - so yes, I think it's probably just personal preference -

also I don't feel it's more work either, but there you go - I understand the physics - perhaps my old MC was so shot anything would have been better!!

Paul