Solid break pedal

[JordanEmbo]

Hi all had the same issue with my Audi for the past 3 years now, break pedal locked up upon breaking and only the hand break would stop me. 
I’ve had a new turbo break servo and vacume pump done by a garage about a year and half ago but same issue has happened again it’s gone solid. The vacume seems to be working as you can hear it hissing the break system has been bled which did have some air in the system but when bleeding the system the break went soft but is now hard again has anyone had this issue before? 

[cliffcoggin]

Jordan. Just to clarify the problem for me, are saying the pedal is really locked solid, immobile, and impossible to move no matter how much force is applied; or is it just very difficult to push down and lacking any servo assistance?

[JordanEmbo]

It pushes down about an inch it sounds like it’s releasing air and that’s it but when you open the bleed nipple it pushes to the floor when I was bleeding the system but as soon as I finished it’s hard again 

[Magnet]

Hello Jordan,

Sounds rather typical of brake servo issues to me - with respect  to the fact that you’ve said your garage replaced it last year. If changing that last time solved the problem then it should be worth returning to the garage and having a chat with them about it. Quality of replacements parts can be variable, and it seems that despite the ongoing hike in part prices, the quality - to be kind - doesn’t seem to improve by the same percentage! 
Perhaps you can let us know what the garage says.

Kind regards,

Gareth. 

[cliffcoggin]

I'd agree there is no servo assistance, and since it is newly repaired I would take it back. Jordan can you hear the servo motor charging the reservoir when the car is first started after standing overnight. It should run about 20 seconds.

[DanY]

I think I'm having the same issue. Brake pedal sounds like it is releasing gas when I press it but then becomes really hard to press it anymore. But interestingly I have found some fluid dripping down the boot of my brake servo behind the brake pedal. 

My thinking is that it must be a master cylinder that's gone bad for it to be leaking fluid. Is that right?

Is it worth replacing the servo as well if there is fluid inside the servo?

I'm going to investigate vacuum hoses tomorrow and I'll check if the servo has fluid in it.

Have I missed anything? Anyone else had this problem?

[cliffcoggin]

Dan.

The brake master cylinder is defintely leaking and needs to be repaired or renewed. I don't see why there should be fluid in the servo but it would not hurt to check.

[DanY]

I checked the servo this morning by dipping a zip tie into the vacuum hose hole. There was no fluid in there which still leaves me confused as to why I have fluid behind the brake pedal. I've ordered a second hand servo and master cylinder anyway, so, with some new brake fluid to go with it I'm sure that will sort it. 

I ended up changing the rear discs and pads today as they needed doing. I found one of the calipers was sticking, I'm not sure if this would lead to excess pressure in the master cylinder hence the ever so slight leak behind brake pedal. 

I'll update when I've fitted the master cylinder and servo. 👍

[DanY]

I realise I have ordered Dot 5.1 brake fluid instead of Dot 4. Will I be alright to use it instead of Dot 4 as I'm going to completely replace all the brake fluid. I'll make a not that it's not Dot 4 for future changes. 

Is there any reason why I can't use Dot 5.1?

[cliffcoggin]

1 hour ago, DanY said:

I checked the servo this morning by dipping a zip tie into the vacuum hose hole. There was no fluid in there which still leaves me confused as to why I have fluid behind the brake pedal. I've ordered a second hand servo and master cylinder anyway, so, with some new brake fluid to go with it I'm sure that will sort it. 

The fluid behind the pedal is because the cylinder is leaking, as I mentioned earlier. It's a common problem on old hydraulic systems and nothing unusual.

A secondhand master cylinder is, to put it politely, unwise. To put it less politely, it is downright foolish to fit equipment that not only may leak as badly as the original, but could in fact fail to work at all when you most need it in an emergency. You may be willing to risk your own life, but please consider the lives of other people in and around the car.

[DanY]

That is a good point. I'll get a new master cylinder.