E90 Brakes/ABS
Discussion
Right, I bought an E91 325i, needing a bit of work and found it actually had no/very little brakes on top of the listed items.. Pedal had little no resistance, and would hit the floor (brakes worked-ish though).
First up.. Bled the brakes through with fresh fluid, which sort of got a pedal, but left it a short while and the pedal vanished. Fluid that came out was in a poor state.
Master cylinder replaced with a 2nd hand item and bled through. Pedal achieved, and stays.. Until you start the car. Then it disappears again. Brakes work-ish and can just about lock the wheels/kick the abs in, but the pedal when pressed sinks, even when you pump it, it still sinks under pressure.
I've driven the car, kicked the abs in (a few times) and tried bleeding again but not getting any more air out.
Now, is this simply a case of needing to bleed the brakes on a machine (although kicking the ABS in would replicate this no?), or am I perhaps looking at an ABS module/pump failure, despite no warning lights, traction/abs/cruise work. When the ABS kicks in you don't get the same feeling as you do on an E46 say, more of a loud whirring noise/sensation as the ABS works, whereas the E46 gives more of a vibration through the pedal sensation.
First up.. Bled the brakes through with fresh fluid, which sort of got a pedal, but left it a short while and the pedal vanished. Fluid that came out was in a poor state.
Master cylinder replaced with a 2nd hand item and bled through. Pedal achieved, and stays.. Until you start the car. Then it disappears again. Brakes work-ish and can just about lock the wheels/kick the abs in, but the pedal when pressed sinks, even when you pump it, it still sinks under pressure.
I've driven the car, kicked the abs in (a few times) and tried bleeding again but not getting any more air out.
Now, is this simply a case of needing to bleed the brakes on a machine (although kicking the ABS in would replicate this no?), or am I perhaps looking at an ABS module/pump failure, despite no warning lights, traction/abs/cruise work. When the ABS kicks in you don't get the same feeling as you do on an E46 say, more of a loud whirring noise/sensation as the ABS works, whereas the E46 gives more of a vibration through the pedal sensation.
Edited by Jhonno on Thursday 25th October 18:46
I haven't worked on one of these, but as far as I understand it there's probably a three way valve between the m/c, wheel cylinder and return circuit which cuts off the brake pedal and lets the pressure bleed out of the caliper. And there's a pump to repressurise the caliper.
If either the valve or the pump leaked, you could end up with a pedal that won't hold pressure.
Equally it could be a worn seal in the m/c that will hold foot pressure with the engine off but not hold the additional pressure when the servo is working.
If either the valve or the pump leaked, you could end up with a pedal that won't hold pressure.
Equally it could be a worn seal in the m/c that will hold foot pressure with the engine off but not hold the additional pressure when the servo is working.
GreenV8S said:
I haven't worked on one of these, but as far as I understand it there's probably a three way valve between the m/c, wheel cylinder and return circuit which cuts off the brake pedal and lets the pressure bleed out of the caliper. And there's a pump to repressurise the caliper.
If either the valve or the pump leaked, you could end up with a pedal that won't hold pressure.
This has some weight the more I think about it and how it behaves.. ABS module/pump replacement.If either the valve or the pump leaked, you could end up with a pedal that won't hold pressure.
The pedal will always be longer with the engine running because of the servo, it should be rock hard and barely move at all with the servo depleted. Make sure you haven’t got a bulging flexi hose or any other obvious issues with any of the calipers.
I’d also be surprised if it’s a fundamental modulator issue, it’s not impossible but I’d expect the internal diagnostics to pick up a major fault and the typical way they fail is simply the brushes sticking in the pump motor which won’t affect the pedal.
I’d definitely get a Bcable and give it an ABS bleed OP, I’ve done a couple of brake kit changes on mine and I’ve never got a good pedal without doing it for whatever reason. Make sure you have plenty of fluid to hand. You also would have been better off bleeding the new M/C on the bench, they’re a pain to get all of the air out of.
I’d also be surprised if it’s a fundamental modulator issue, it’s not impossible but I’d expect the internal diagnostics to pick up a major fault and the typical way they fail is simply the brushes sticking in the pump motor which won’t affect the pedal.
I’d definitely get a Bcable and give it an ABS bleed OP, I’ve done a couple of brake kit changes on mine and I’ve never got a good pedal without doing it for whatever reason. Make sure you have plenty of fluid to hand. You also would have been better off bleeding the new M/C on the bench, they’re a pain to get all of the air out of.
Edited by The Wookie on Friday 26th October 07:33
The Wookie said:
The pedal will always be longer with the engine running because of the servo, it should be rock hard and barely move at all with the servo depleted. Make sure you haven’t got a bulging flexi hose or any other obvious issues with any of the calipers.
I’d also be surprised if it’s a fundamental modulator issue, it’s not impossible but I’d expect the internal diagnostics to pick up a major fault and the typical way they fail is simply the brushes sticking in the pump motor which won’t affect the pedal.
I’d definitely get a Bcable and give it an ABS bleed OP, I’ve done a couple of brake kit changes on mine and I’ve never got a good pedal without doing it for whatever reason. Make sure you have plenty of fluid to hand. You also would have been better off bleeding the new M/C on the bench, they’re a pain to get all of the air out of.
It is rock hard without the engine running.. It is longer to the point of hitting the floor whilst running, with very little resistance. You can't even pump them up.I’d also be surprised if it’s a fundamental modulator issue, it’s not impossible but I’d expect the internal diagnostics to pick up a major fault and the typical way they fail is simply the brushes sticking in the pump motor which won’t affect the pedal.
I’d definitely get a Bcable and give it an ABS bleed OP, I’ve done a couple of brake kit changes on mine and I’ve never got a good pedal without doing it for whatever reason. Make sure you have plenty of fluid to hand. You also would have been better off bleeding the new M/C on the bench, they’re a pain to get all of the air out of.
Edited by The Wookie on Friday 26th October 07:33
Bcable? Currently trying to sort INPA or similar to get it to bleed, but I only have a Apple laptop thing to hand as all my proper laptops died!
I never realised this.. Wish I had of beforehand..
Jhonno said:
It is rock hard without the engine running.. It is longer to the point of hitting the floor whilst running, with very little resistance. You can't even pump them up.
Bcable? Currently trying to sort INPA or similar to get it to bleed, but I only have a Apple laptop thing to hand as all my proper laptops died!
I never realised this.. Wish I had of beforehand..
That’s a little strange I’ll admit but I’d still give the ABS bleed a go, you never know where the air might be trapped, and if you’ve changed the M/C you can guarantee there will be somewhere!Bcable? Currently trying to sort INPA or similar to get it to bleed, but I only have a Apple laptop thing to hand as all my proper laptops died!
I never realised this.. Wish I had of beforehand..
Sorry Bcable is just an INPA usb cable. If you’re based around Tamworth you’re welcome to borrow mine as my E92 is down in Reigate anyway at the moment!
Sorry, it’s amazing how few people actually do it that way! The ABS bleed chews through a lot of fluid, you might find it does the job in the process!
The Wookie said:
That’s a little strange I’ll admit but I’d still give the ABS bleed a go, you never know where the air might be trapped, and if you’ve changed the M/C you can guarantee there will be somewhere!
Sorry Bcable is just an INPA usb cable. If you’re based around Tamworth you’re welcome to borrow mine as my E92 is down in Reigate anyway at the moment!
Sorry, it’s amazing how few people actually do it that way! The ABS bleed chews through a lot of fluid, you might find it does the job in the process!
I'll give it a bleed and see.. Shame you can't just bridge the relay like you can on the E36/46.. I mean you can pump it up a bit, but it doesn't make the brakes work any better, and it immediately vanishes.. Sorry Bcable is just an INPA usb cable. If you’re based around Tamworth you’re welcome to borrow mine as my E92 is down in Reigate anyway at the moment!
Sorry, it’s amazing how few people actually do it that way! The ABS bleed chews through a lot of fluid, you might find it does the job in the process!
Ah! I see.. Bummer, I am in Essex! Thanks for the offer though!
Fingers crossed.. Swapping out the ABS module isn't that hard luckily if it came to that!
Jhonno said:
So.. I had a theory.. I pulled the ABS fuse, to see what happens with the ABS deactivated..
Result.. Exactly the same. Would this point towards the 2nd master therefore being bad too? Or have I wasted 10 minutes of my life?
To be fair the ABS doesn’t interfere with the brake line unless it’s actually doing it’s business so it doesn’t tell you anything. I’d still stick to getting a better bleed before you do anything else! Unlikely you have two dud M/Cyls I would have thoughResult.. Exactly the same. Would this point towards the 2nd master therefore being bad too? Or have I wasted 10 minutes of my life?
The Wookie said:
Jhonno said:
So.. I had a theory.. I pulled the ABS fuse, to see what happens with the ABS deactivated..
Result.. Exactly the same. Would this point towards the 2nd master therefore being bad too? Or have I wasted 10 minutes of my life?
To be fair the ABS doesn’t interfere with the brake line unless it’s actually doing it’s business so it doesn’t tell you anything. I’d still stick to getting a better bleed before you do anything else! Unlikely you have two dud M/Cyls I would have thoughResult.. Exactly the same. Would this point towards the 2nd master therefore being bad too? Or have I wasted 10 minutes of my life?
However, I will get a pressure bleeder and INPA up and running.
Jhonno said:
I wasn't sure how sound my logic was.. The only thing is, I have activated the ABS (braking on grass) as the diagnostics would to bleed it, and I got no extra air out.
However, I will get a pressure bleeder and INPA up and running.
To be fair I’ve tried skipping using the INPA routine by going up the road and triggering the ABS a few times and it doesn’t work on the E92However, I will get a pressure bleeder and INPA up and running.
The INPA routine sounds and seems like it’s doing a lot more than just triggering the valves as it would during normal operation, it asks you for different pedal positions and chews through masses of fluid in the process.
Make sure you have a helper to crack the bleed nipples open on the calipers while you’re sat in the car!
Right.. Bled through with INPA.. No brakes. Well, improved braking, but a complete lack of pedal still, and the pedal will sink.
Another master ordered, you can't get these new it seems! Or they are big money.
New master ordered, bled through (once so far) with INPA.. Guess what. Still no brake pedal.
Another master ordered, you can't get these new it seems! Or they are big money.
New master ordered, bled through (once so far) with INPA.. Guess what. Still no brake pedal.
Really?? Did you bleed the master off the car?
Assuming you haven’t got a very badly bulging flexi hose the only other thing left would be the ABS... really though I can’t think how it could possibly create this failure! If a valve was stuck and it was exposing the pedal to one of the accumulators it should pick it up on the startup diagnostics and put the ABS lamp on...
Assuming you haven’t got a very badly bulging flexi hose the only other thing left would be the ABS... really though I can’t think how it could possibly create this failure! If a valve was stuck and it was exposing the pedal to one of the accumulators it should pick it up on the startup diagnostics and put the ABS lamp on...
Right.. Bled through with INPA.. No brakes. Well, improved braking, but a complete lack of pedal still, and the pedal will sink.
Another master ordered, you can't get these new it seems! Or they are big money.
New master ordered, bled through (once so far) with INPA.. Guess what. Still no brake pedal.
Another master ordered, you can't get these new it seems! Or they are big money.
New master ordered, bled through (once so far) with INPA.. Guess what. Still no brake pedal.
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