Help with a mystery
 

Rover 75 buddies i need some help on issue that is starting to drive me up the wall

Firstly my R75 DERV Tourer back brake pipe went, no big deal that happens so it went into the garage

when there it had new brake pipes , new caliper and bled

however on return it did this

brake pedal worked as you pressed and after two seconds started to sink to the floor, not entirely to the floor boards but sank slowly. checked and no air in the system, so the garage said it may be a seal on the master cylinder, so i said ok lets get one then so we got one and also placed three new vacuum tubes on the servo also .... wait for it

tried it again with all that done.....two seconds sank again, its not leaking and no air in the system.... so back to the drawing board, this time the garage said the T4 is not talking to the ABS system so may be its now gone as the fluid all drained out from the brake pipe going at this point i said i cannot believe a broken brake pipe would knock out the entire braking system... so in the end i said ok lets get the ABS off my donor which i knew it worked....

placed that on the car... wait for it.... same again two second brake pedal sank slowly, so now i have had brake pipes, three vacuums pipes , ABS system, master cylinder, caliper, and new fluid and brake system bled....

the garage then said the servo must be gone....i said i just cannot believe this, and said hold on lets not change this yet... the two mechs are good guys however we seem to be stumped on this.... can anyone let me know what is going on here, because i fear the worst if we change the servo again nothing will change HELP!!! ROVER 75 buddies

MY BRAKES ARE SLOWLY SINKING? ON THE FOOT BRAKE PEDDLE.

Search for sinking pedal syndrome, ie https://www.the75andztclub.co.uk/for...ad.php?t=63314

i thought that like in the MOT quick test , pump up the brake pedal first , then hold it down and start the engine , it should fall . that is for petrol engines. you have diesel so im not sure if they have a vacuum pump system instead. Another diesel owner would know as i have never owned one. !! if the garage boys know their stuff, they would have checked for hose leakage , and that the servo is functioning or not. Its always a bad policy to just exchange parts at random for elimination. Not to mention parts and labour costs. have they run any checks on the servo ? What was their prognosis ? i would certainly ask a few more questions , before opening your wallet again. ...

the sinking pedal syndrome is a common topic on here ,especially on automatics. mine has always done this very slightly on my auto,but never been a problem. you seem to have a floppy pedal for another reason. some say that the ABS cannot be purged of air , some say it can with T4.. .. :shrug:

Have a read of these threads, have the garage done anything like damaging the servo?

https://www.the75andztclub.co.uk/for...d.php?t=318553

If not then look at this thread, taking notice of how Jules does his bleeding.
https://www.the75andztclub.co.uk/for...ad.php?t=63314

Thanks Artic, the garage have used T4 to push the air out the ABS and the T4 shows no air however nothing has improved and the 3 vacumn pipes all been replaced and the ABS unit and the Master cylinder only the servo left and to be honest i dont think its that anyway

im stumped also on this

hi arctic. Does the diesel have its own vacuum pump system to generate the required effect ? could that not be working or not show open cicuit on T4 ?

Hi Stefan.
The servo is connected to the EGR solenoid through the vaccum hose top one is the R40 M47 solenoid the bottom one is the Freelander 1 solenoid

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

from the solenoid
https://i.imgur.com/PFTUvgDl.jpg2

It joins to a one way valve, which is connected to the servo.
https://i.imgur.com/VGFgmHrl.jpg3

Usually if the hose as chaffed /worn through the brakes go harder but to do not go slowly to the floor.

The OP says he as changed the vaccum hoses.

You can see from these photos that the hose as worn through i found this on a local owners car, i doubt many members /owners check these hoses.
https://i.imgur.com/KDWUr0Tl.jpg4

https://i.imgur.com/FoQMoKpl.jpg5

https://i.imgur.com/H9EtGAUl.jpg6

Something as gone wrong when the garage have changed the brake pipe on the car, either it's not been bleed correctly or they have damaged the servo?

Have the garage carried out a full brake bleed as per RAVE using the T4 with the new ABS pump installed?

If not that is the way to go.

sinking brake pedal
 

I am a retired mechanic with over 60 years in the trade and when ABS came along the sinking brake pedal problem seamed to get more frequent I found out when bleeding the brakes if I clamped the flex pipe & opened the bleed nipple to release the fluid when changing pads etc then remove the clamp from the brake pipe to bleed the brakes never had the problem it is the pushing the fluid back through the system that's the problem you can flip a seal in the ABS or master cyl that's my thinking anyway but what do I know I'm 84 years old