Wooden brake pedal and hard to stop!

[dodge1979]

Guys, nearing the final hurdles on my rebuild of the S4, the brakes were bled today. To the letter of the manual with my trusty assistants foot..I did the whole procedure twice through. But upon the first test drive this evening the brake effect is poor. The pedal feels wooden and the brakes arnt stopping the car well, you really have to push hard! The twice bleed removed all air, I believe. The rear calipers are brand spanking new, as are all front and rear discs and ebc yellowstuff pads. The accumulator does its buzzing thing as and when its supposed to during the bleeding procedure and stops when its supposed to. The ABS light is on though. All ABS sensors were cleaned and two were replaced with new during the rebuild. Are they adjustable for distance to the toothed ring they read off I wonder...

So my question is...can anyone suggest possibly causes for this rubbish braking effort? preferable without saying I need to spend a grand and a half on a new abs accumulator assembly!

cheers

Darren

[mdw]

I cant remember the colour order but are the yellow stuff pads the track ones which need heating up a bit before they work properly. Or has the wear in coating worn of the pads properly. Just a guess.

[dodge1979]

Hmm, I thought the yellowstuff was suitable for road use, the wear in coating was removed from the front ones prior to installation..I needed a fraction more room or they were too tight..The brakes are making a 'rotating' noise, which suggests as they have sat for months before beiing used they all need bedding in yes, but I suspect the pedal feel and poor brake performance is a little more then just that

[andydclements]

Did you follow the process for bleeding that type of assembly (can't recall what it is as i don't EVER plan to have one of those types)?

[RV_ABZ]

Do you have brake assistance? You speak about wooden pedal and having to press hard on the pedal, as if no assistance at all. Defective pressure switch?

Edited May 25, 2011 by RV_ABZ

[Rich H]

I found that the only way to bleed the rears properly was to dump the pressure, open the front bleed nipples up to remove any resistance from them then bleed the rears.

Once that is done then fill it back up with fluid and bleed the fronts.

Took ages...

How about putting Espritmon on and reading the ABS computer find out what's up with it?

[Bibs]

Yellowstuff are perfectly fine for road use. Perhaps 10 years ago they needed warming up but the compounds on all EBC pads is essentially the same, it's the backing that changes (more temp resistance) as you head up the range.

[dodge1979]

Yes followed the instructions in the workshop manual to the letter..twice over..and yes it feels like there is no assistance..ive got to go and get my disc and manual back off Mike at Lotusbits as I lent it him months ago :s, gotta check out the random engine check light too. I did notice though the ABS light goes out sometimes too, but hasnt always. I havent had chance to try driving it again, just been trying to sort out the clutch peddle bite being on the floor...

Would the pressure switch when its not working still allow the accumulator to start and stop as it should and the relays to work as normal? I know im going to have to read the secong workshop manual now for the braking system

[dodge1979]

Well having gone through the braking system again, I cant find any faults with reklays or the accumulator getting up to pressure..so rebled them again. However this time I feel the pedal has improved from tyhe wooden one before....BUT I cant test them on the road yet until the annoying clutch issue is sorted...which has turned out to be a defective new slave cylinder. So moral there is that you cant always assume a new part is working correclty..check them also! When the new one turns up Ill hopefully get a clutch pedal and some brakes that work!

[G_Reaper]

Hi Darren

I took the advice of Sanj having tried bleeding my clutch by using a professional pressure system I swapped back to the good old mechanics assistant pushing the pedal and this sorted my clutch hydraulic problems. I hope this helps when you get your new part.

I have ditched the ABS and retro fitted the earlier Stevens master cylinder and servo. The master cylinder can be bought new for approx £35 the servo is off a Renault extra van. Douglas Valley Breakers have the full set up with the mounting bracket for £75 (thats the most reasonable price I have ever had from them). Then you need a vacuum supply which Martin L and myself may have finally sorted. Let me know if you wish to go down this route.

Cheers Mike

[ramjet]

I have the original brakes (Brembo with the ABS) on my S4. I completely changed all the fluid on mine when I replaced the accumulator. I know for a fact that my pressure switch is going a bit soft on the high pressure side. I followed the manual when I bled my brakes and have not had any trouble with them at all. They do not bite like some modern cars but are progressive and I know what they're going to do each time I press on the pedal. I have never really understood what people mean when they say wooden.

When you say you followed the manual, I presume you also made sure to bleed the master cylinder using the bleed screws on it?

[G_Reaper]

My S4s brakes were rubbish.

Push the pedal and the pedal was quite hard and you felt the car braking quite well, then you push a little harder for more bite and you felt like the brakes were not relaying the braking force you were putting into the pedal with your foot into stopping force, as if the brakes were using wooden block friction material to stop the car.

The immediate reaction of the brakes was not linear through out the pedal travel and the feedback was poor. Then at other times you would be driving along having used the brakes as normal all seemed ok then you would arrive at a junction where you need to stop a little bit briskly, you would push the pedal the car would start braking reasonably well then the pedal would drop underneath your foot. Panic then takes over as you think your brakes have failed only for the pedal to firm up again before the pedal hit the carpet. then the car would stop.

Sometimes sitting in traffic foot on the brake with the car stationary the pedal would drop slightly causing concern. I tried all sorts, cleaning the pressure switch replacing the accumulator bleeding the brakes etc etc. So I gave up, I had lost complete faith in the system. Too old and too complicated to get a simple job done effectively with good feel that gives you confidence.

That was my experience.

Cheers Mike

[ramjet]

Fair enough Mike. Some of those things would be a concern. Mine have never done anything like that except for when I had the accumulator give up and the pump ran every brake press. Other than that, nothing.

[dodge1979]

Guys, thanks for all the comments and views above..well last week week I rebled them again, and as before exactly as per the manual. This time however I got the brake feel I was hoping for. The car went through Its first MOT in 3yrs without issue...although the ABS light is one Took her out today for the first time for a little get used to drive..brakes sound. Stopped to put some juice in....bouncy bouncy fuel gauge fun...On way home brake pedal went wooden again with no feel and I was stamping on them to bring to a halt!!!

It turns out that the accumulator wasnt running on the way home..hence the bad pedal. Now a nose about has revealed that if I wiggle the wiring plug that goes onto the front of the accumulator then it activates it. So, I wiggled each of the three wires in turn..no activation, but upon trying to unplugg the plug the accumulator started pumping up...so it would seem the three pins on that plug or the switch/sender that its connected to are not making a tight contact! Tomorrows issue to sort out there!

[G_Reaper]

The plug you talk about I think plugs onto the dreaded pressure switch. if it is not just a dodgey plug or wire then it will be the switch. If that's the case you have a few options :-

1)Try cleaning the switch as per instructions on this site. (Has worked for some people)

2)Wait for Lotus to bring out the replacement switch (The wait is currently getting on for 2 years I think and it wont be cheap)

3)By the twin switch system from Australia (A little on the expensive side)

4) Remove the ABS and go for a standard set up

Cheers Mike

[dodge1979]

Mike, interesting...does anyone have the easy to do link for the cleaning thread??or shall I search till the wee hours of the morning...you mention a double switch system...where is that from? Although I did a little cleaning myself today..tried the accumulator again by depressuring it, turnin on the ignition...wiggle the plug it built up pressure....stopped when I pulled the plug out, put it back in wiggle, started again, with ignition on pressed the brake pedal several times...well quite a few till it lost all assistance...no accumulator being repressurised.....wiggle wiggle...build up pressure....you get the idea? Now, checked the wires were tight, the terminals sound....sprayed with cleaning/lubricating fluid...plugged in..worked straight off. depressurised the system...ignition on..build up pressure straight off...with ignition on depress the pedal a few times, accumulator comes on to build the pressure up...repeat, again works, repeat again works...depressurised..did it all over again..no problems,,,,left it for a bit did it all over again no problems.

Sorry that was a boring paragraph but you get he idea of what Im doing...maybe just a dry connection or dirty...if Im lucky maybe!!! We shall see over the weekend so long as it doesnt rain!