Almost ready for the mot, brake pedal?
 

Hi all,

Been busy over the past week or so (on and off).
New upper rear arms (courtesy of dmgrs)
Rear springs,
New copper brake lines from abs module to rear Flexi hoses
New drivers side lower arm and bush
New MAF sensor
New mintex discs and pads all round
Cavity wax injected in sills, inside new rear upper arms, jacking points and inside the doors
Wheel arches and underside cleaned dried and waxoyled with two coats.
Brake fluid flushed (old fluid was rather dark looking). (Hoping this may just cure my weird abs fault warning that flashes up for a second in heavy rain).

The mot runs out tonight at midnight so took it out for a short drive and noticed the brake pedal is firm, so want to ask others after fitting new brakes and fluid etc how they "should feel".

Driving along - near the top of the brake pedal travel, the brakes begin to slow the car down very slightly. Apply a little more force and the brake pedal becomes quite firm but still slows the car (feel quite wooden when applying force).
Abs works fine at different speeds, stops straight etc). Is this how they should be?
The brake begin to act almost as soon as you apply light pressure to the pedal with no real pressure from your foot but anything after this require quite a bit more pressure and as I say, feel wooden.

Thanks
Rob

Firm brake pedal and wooden feeling usually points to servo and or servo pipes, check for pipes leaking (meaning no vacuum to the servo).when engine is off pump brake pedal until firm then start engine pedal should gain some travel (softness)if not probably a servo or pipe problem :}
Just noticed it's a diesel not that familiar with cdti's check vacuum pump if fitted also :}

Is the servo working ok ? im a petrol head and there are posts on here how to check the servo function of diesels and what to check. Have a google on the search bar. Hope the pistons were nice and free in and out , when you did pads and discs. Sometimes even though they move in and out , they can be lazy when dirt has embedded inside the cylinder. You wont necessarily have brakes pulling to one side , but are just lazy. If the fluid was as dark as you say , when it came out, then there is a big possibility that they need a refurb kit or at least a good clean out.

Hi Rob.
Check the vacuum hose coming from the EGR solenoid they can chaff and get holed casing such a feeling.

https://i.imgur.com/KDWUr0Tl.jpg1

https://i.imgur.com/KDWUr0Tl.jpg2

https://i.imgur.com/PFTUvgDl.jpg3

https://i.imgur.com/VGFgmHrl.jpg4

Hopefully when you pushed back the caliper piston if you did ? when changing the pads and discs you have not flipped a seal, which i doubt as that feeling is different, it does sound like vacuum maybe the one way valve as failed ?

Thanks for the reply 👍 I can confirm, pumping the pedal with the engine off, the pedal goes rock hard, starting the engine and the pedal softens up and sink approx 2 inches.
One thing I forgot to mention in my first post, when replacing one of the rear discs, I changed the pads and pushed the piston back in without first removing some fluid from the reservoir first, after pushing the piston back in, I suddenly realised and checked and found the fluid level with the cap. (Just hoping I haven't forced fluid somewhere it shouldn't be).

On a second point can toaf operate the abs module for bleeding the secondary circuit?

Thanks arctic, I'll check this tomorrow, I know our tourer has had the egr bypassed by a previous owner. The small fabric hose you show, our tourer has the yellow plastic plug in the end.

after speaking with others and doing more reading, id like to quote bigruss (hope you dont mind russ if your reading this :}

"Today I've been fitting new calipers to improve the brake performance of the front brakes, one of them was sticking slightly.

Hoses clamped off and calipers changed with no problems

Time to bleed the brakes and thought I'd do it properly on the T4, the sequence is as follows:

Select brake to be bled on screen menu after fitting bleed tube to bleed nipple.
Open bleed nipple and depress pedal to expell air until it runs clear ensuring resevoir is topped up.
Next press continue on the T4 menu to bleed the secondary circuit with the ABS pump until clear.
Finally tighten bleed nipple while pedal is depressed.

All was going well until it came to bleed the secondary circuit........... Absolutely full of air

Took a total of 4 bleed sequences on each side to get it free of air and 1/2 litre of fluid.
The pedal is now solid when depressed.

The problem for members is that normal bleeding or pressure bleed kits only bleed the primary circuit, in order to bleed the secondary circuit you will need to use suitable diagnostic equipment capable of using the ABS pump to bleed it properly.

I wonder if this is why some owners suffer from sinking pedal syndrome.

Russ"


after flushing the old "tea/coffee" coloured fluid out yesterday and appearing to successfully bleed each corner using the correct sequence. i can confirm the following:

Engine OFF:
brake pedal goes down slightly (servo air wushing noise can be heard) had this on all the 75s ive had.

press the brake pedal 3-4 times and leave overnight, the brake pedal is still rock hard. start the car with your foot on the brake and the pedal does sink by around 3 inches and then stops. - it doesn't sink any further. no where near the carpet. (i have experienced this on other cars too. engine off- pump pedal - now rock hard at the top, foot on brake, start engine, pedal falls away slightly and then stops and doesnt sink any further.

driving - abs works and stops the car in a straight line.
placing your foot on the pedal, slight pressure (taking up the spring on the back of the brake pedal) now pressing beyond this and the brakes begin to act - brakes acting right at the very top of the pedal travel. applying a little more pressure and the pedal does require more force but the brakes slow the car quicker.

i know this is simply repeating my original comments however as bigruss stated in his thread about bleeding the secondary and having a much firmer brake pedal, im just wondering if this is what i am experiencing as i cant imagine my brake pedal being much firmer so not sure if im just experiencing new brakes and panicking for nothing?
perhaps the best thing i could do is have a t4 carried out just be on the safe side?)

is toaf able to perform the abs bleed?
also checked the servo and vacuum hoses and the small fabric covered hose that runs to the egr (mine bypassed) and all is well thankfully.

previously the brakes were softer/supple but the discs were badly warped. new brakes - harder pedal, less of the supple feel through the pedal

Hi Dave.
Yes that was dougie's car, i did not have any hose with me at the time, when i usually carry a roll which i have rectified this time round for tomorrow ;)

Not had a chance to look at the car properly, this evening I had to move the car on the drive to swap wheels over on to the wife's 75 (her car has mot and had a puncture) anyway, before I even put the key in the ignition I tried the brake pedal and noticed the pedal was rock hard (as if I'd pumped the brake pedal up then left it parked).

Anyway, swapped the wheels over etc and again, noticed the brake pedal had gone hard again as if it was pumped and left hard again.

Not sure if this points to something but the wife's 75 doesn't do this.

Start the engine the brake pedal drops as id expect it to and the servo can be felt and heard working too.

I'm hoping to have a look at it tomorrow