Brake Booster/Servo Issues.....

warren9022

Registered User
Been having problems with braking lately, pedal going hard under heavy or sustained braking that feels like a loss of vacuum.

Have changed all the vacuum hoses from the inlet manifold to the brake booster/servo but problem still exists and now showing fault code:

00812 - Brake Pressure Release Solenoid (F84)
Possible Causes
  • Switch for Brake Recognition (F83) faulty
  • Wiring to Switch for Brake Recognition (F83) faulty
  • Brake Booster faulty
Possible Solutions
  • Check Switch for Brake Recognition (F83)
  • Check Wiring to Switch for Brake Recognition (F83)
  • Check Brake Booster
As my brake switch works perfectly I'm assuming it's the brake booster/servo (part number 8N2 614 206)

Have enquired with the stealers and the booster/servo is a discontinued item, can't find any decent second hand ones (seeing as you have to drop the engine to change it according to Elsa-win I don't really want to put a second hand one in anyway, I'd rather put a new one in and fit and forget).

Can find aftermarket ones from ATE but only for LHD cars which seems slightly ridiculous so my questions are........

Has anyone ever sourced a new brake booster/servo for a RHD car? If so where from as I'm going round in circles at the moment!!

Also has anyone ever had the 00812 fault code and solved the issue without having to change the brake booster/servo?

Thanks in advance.
 

warren9022

Registered User
Have you tried TPS? Or if ur on face book then there is a online branch of them called *** they might be able to help.

Yeah it was Mike at *** that gave me the bad news it was an obsolete item. Refuse to believe they make an aftermarket one for a LHD car and not a RHD, will do some more digging. I’d rather take it off the road temporarily than put another 18 year old servo on it :shrug:
 
That's is strange that they have ones for LHD and not a RHD. I would rather get a new one myself instead of 17-19 year old one.
Hope you get do find some where to get a new one from.
 

Tj 0785

Registered User
VCDS Map User
Silver Supporter
I’m sure I read that people would fit one off a transporter t4 to improve pedal travel on the 18z calipers so maybe they fit
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
When I looked into the T4 cylinder thing the ones I found were ESP compatible... There maybe a version out there that has the support for the pressure switches required for the ESP system...

I coded my ESP out a long time back but not sure if that means I could potentially run without these sensors connected... I guess its plausible it could work...

<tuffty/>
 

warren9022

Registered User
Thanks @<tuffty/> . Going to change the brake switch first just to eliminate that and it’s cheap to change!! Can’t see it having any effect but I’ve overlooked the cheap, obvious solution before and regretted it.......

Then if the brakes are still **** I might change the master cylinder and pressure sensors to see if that makes a difference. In all my searching of the net for a replacement booster/servo I haven’t come across one person who’s had a faulty one so I’m keeping my fingers crossed it’s something else :racer:
 

warren9022

Registered User
Have you solved this yet warren I have this issue also :-(

No mate, still ongoing. I've changed the brake switch, all vacuum piping to the servo, checked all the one way valves and the brakes are still shockingly bad!! All clues lead to a faulty servo.

Still not found a new or reconditioned aftermarket servo and to be honest it's taken all the fun out of driving the car so it may be the end of my relationship with the S3 as I refuse to replace the servo with one of the same age.

If you manage to solve it let me know.
 

Nathxn__

Registered User
Hi mate do you have a PCV delete at all? I do & I’ve had some good results I installed an extra one way valve on the brake servo pipe that connects to the inlet manifold. Not sure if this is needed but I think it’s helped somehow.

What are the condition of your brake discs/pads like?
My front discs/pads were shot I changed them today and all though I’m still bedding them in the pedal feels nice & high again since doing this...hope this might help
 

Nathxn__

Registered User
I also tested my brake fluid with a tester and it said it had too much moisture in it so I replaced all fluid bled all 4 callipers & master cylinder
 

warren9022

Registered User
Hi mate do you have a PCV delete at all? I do & I’ve had some good results I installed an extra one way valve on the brake servo pipe that connects to the inlet manifold. Not sure if this is needed but I think it’s helped somehow.

What are the condition of your brake discs/pads like?
My front discs/pads were shot I changed them today and all though I’m still bedding them in the pedal feels nice & high again since doing this...hope this might help

I also tested my brake fluid with a tester and it said it had too much moisture in it so I replaced all fluid bled all 4 callipers & master cylinder

Hi mate, pads and discs are about 6 months old and done about 1000 miles. Had the brake fluid flushed about 18 months ago, tested it a few weeks ago and there’s no moisture in it. Replaced the hose that goes directly to the servo with a brand new genuine one so the one way valve is brand new, have only ever run the one as it’s all that’s needed. I’m out of ideas to be honest. Hopefully you’ve got a different issue to me and the new pads and discs solve it, let me know after you’ve driven it for a while :icon thumright:
 

himself26

Registered User
Just had what seems to be the exact same issue warren9022,
Culprits on my car were as follows.
Elbow bend under the inlet was split on the bend so hard to see unless opened up part number is 06A-133-783AS
The other air leak was the main servo pipe that runs from the lhs of the inlet the actual hard plastic pipe. It had opened up (expanded) on the joint right in the corner of the engine bay just above the brake master cylinder where it meets the bulk head servo pipe.
It was still connected but not where you'd expect a leak so easily overlooked.
Maybe worth checking ???
 

warren9022

Registered User
Just had what seems to be the exact same issue warren9022,
Culprits on my car were as follows.
Elbow bend under the inlet was split on the bend so hard to see unless opened up part number is 06A-133-783AS
The other air leak was the main servo pipe that runs from the lhs of the inlet the actual hard plastic pipe. It had opened up (expanded) on the joint right in the corner of the engine bay just above the brake master cylinder where it meets the bulk head servo pipe.
It was still connected but not where you'd expect a leak so easily overlooked.
Maybe worth checking ???

Thanks for the input @himself26 , the car has had a PCV delete so I know there's no leaks under the manifold.

I'll check the hard plastic pipe, when you say yours had 'opened up' do you mean it had split? Did you have to replace the pipe?
 

himself26

Registered User
Thanks for the input @himself26 , the car has had a PCV delete so I know there's no leaks under the manifold.

I'll check the hard plastic pipe, when you say yours had 'opened up' do you mean it had split? Did you have to replace the pipe?

It hadnt split m8 it had expanded with the heat in the engine bay. Thats how it was initially over-looked. I've simply put a jubelee clip on for now but im going to alloy & silicone pipe it when i get round to it ;)
 

Nathxn__

Registered User
Hi mate I’ve had another development with the s3..do your brakes overheat at all? Mine were which I’ve determined was my issue..the brake fluid pot was overfilled causing all calipers to stick, check your pot is not over filled
 
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