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Discussion Starter · #1 ·
So it looks as if my brake pressure sensor(s) on the master cylinder are playing up.
The ESP light came on last week and after scanning it with VCDS the code P01435 Brake Pressure sensor 1 (G201) Intermittent electrical fault was found.
Having checked the measuring blocks for the G201 switch the pressures were bouncing around with the brake pedal depressed so I'm fairly certain the switch is faulty, it seems to be in the early stages of failure though as turning off the ignition and re-starting clears the ESP light.
This brings me to my question , the plan is to DIY replace both switches with Genuine items and to carry out a full brake bleed, so how much of a pig is this job?
I know all the reservoirs for coolant , PAS and other stuff in that area need to be drained or at least moved out of the way , but have just read an old thread on here about removing the engine mount and jacking up the engine just to get access?
Having done all that on a recent cam belt change I don't really want to go through all that again .
I'd appreciate any pointers from someone who has done this themselves .
Thanks!
 

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My local indie did both of mine last year. He rated it as a PIA, and his workshop is very well equipped. Cost was £482, inc parts and vat.
Mac.
 

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Discussion Starter · #3 ·
PlasticMac said:
My local indie did both of mine last year. He rated it as a PIA, and his workshop is very well equipped. Cost was £482, inc parts and vat.
Mac.
Thanks for the info ....
Genuine sensors are £80 each so it'd cost me £160 plus the cost of brake fluid and my time.
I hate paying anyone to do work that I can do myself, it's just I'd like to really know if it's a nightmare job before I attempt it.
I felt the same way before doing the cam belt and water pump , and that worked out fine.
 

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I did it on a friend's car and I'd rate it about a 7 (out of 10). You have to remove the plastic shroud round the fuel / evaporative emission pipes (don't get them mixed up) and then it's not too bad. His car wasn't a 225 though so it may not be quite the same - the charge pipe will have to come off for starters.
 

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I was quoted approx £500 to change both sensors at an Indi - DIY cost me nothing - in fact I made a profit with the sale of surplus OE sensors (bought 4x genuine for £10 ea. from a VAG dealership).

Entirely possible as a DIY job - buy the parts/tools you'l need in advance and recommend a pressure bleeder like the SEALEY one I used.

Buy a replacement securing bolt for the reservoir as engaging that in the thread is perhaps the fiddliest job and its likely you'l drop it - think mine fell into the hole in the chassis box section! - I had to then wait a week for a replacement!

https://www.ttforum.co.uk/forum/viewtop ... &start=675
 

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Discussion Starter · #8 ·
John949 said:
I did it on a friend's car and I'd rate it about a 7 (out of 10). You have to remove the plastic shroud round the fuel / evaporative emission pipes (don't get them mixed up) and then it's not too bad. His car wasn't a 225 though so it may not be quite the same - the charge pipe will have to come off for starters.
Thanks , that reassures me , certainly seems within my capabilities :p .

DC240S said:
I was quoted approx £500 to change both sensors at an Indi - DIY cost me nothing - in fact I made a profit with the sale of surplus OE sensors (bought 4x genuine for £10 ea.).

Entirely possible as a DIY job - buy the parts/tools you'l need in advance and recommend a pressure bleeder like the SEALEY one I used.

Buy a replacement securing bolt for the reservoir as engaging that in the thread is perhaps the fiddliest job and its likely you'l drop it - think mine fell into the hole in the chassis box section! - I had to then wait a week for a replacement!

https://www.ttforum.co.uk/forum/viewtop ... &start=675
Thanks, you did well to get those sensors for a mere tenner , the cheapest Genuine I could find were £80 each :cry: .
No way am I going to fit repros off eBay as they all seem the same items from China , just at different prices.
Sadly the reservoir securing bolt appears to be NLA.
I see from your thread that you only bled the master cylinder , front calipers and clutch?
Did you not do the ABS pump bleed?
That looks a worse job than the sensors :lol: .
Lastly, Bentley says the torque for the sensors is 10ft/lbs , is there space to get a socket/torque wrench in there or do you have to guesstimate and did the new sensors need calibrating with VCDS once fitted?
Thanks .
 

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silverbug said:
Thanks, you did well to get those sensors for a mere tenner , the cheapest Genuine I could find were £80 each :cry: .
No way am I going to fit repros off eBay as they all seem the same items from China , just at different prices.
Sadly the reservoir securing bolt appears to be NLA.
I see from your thread that you only bled the master cylinder , front calipers and clutch?
Did you not do the ABS pump bleed?
That looks a worse job than the sensors :lol: .
Lastly, Bentley says the torque for the sensors is 10ft/lbs , is there space to get a socket/torque wrench in there or do you have to guesstimate and did the new sensors need calibrating with VCDS once fitted?
Thanks .
Use genuine sensors supplied from TPS or VAG dealership or other confirmed VAG source - there are some convincing chines copies on eBay.
Strange on the bolt - have you tried Coverdale parts?
No need to bleed the ABS pump - there was a reason as I remember - perhaps because the system is bled before and the unit isn't cycled through the process?
Torque was indeed approximate - no access for the torque wrench I have.
No VCDS calibration required - just a code scan and clear down.

DC
 

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Discussion Starter · #11 ·
davebowk said:
Thanks, I saw those but I *think* they're Chinese, having seen them for £13 on AliExpress I'm of the opinion that all the cheap ones on eBay are Chinese.
I've gone for 2 from Stafford Audi , via eBay again but at £80 each by far the best price I could find , for Genuine Audi/ATE at least .

DC240S said:
Use genuine sensors supplied from TPS or VAG dealership or other confirmed VAG source - there are some convincing chines copies on eBay.
Strange on the bolt - have you tried Coverdale parts?
No need to bleed the ABS pump - there was a reason as I remember - perhaps because the system is bled before and the unit isn't cycled through the process?
Torque was indeed approximate - no access for the torque wrench I have.
No VCDS calibration required - just a code scan and clear down.

DC
Thanks that's really useful info , I'm going to get one of those Sealey gizmos you mention , I do have an Ezibleed but the Sealey looks much better.
It is odd about the reservoir bolt (1J2 611 353) , I was given a price this morning at my local VW main dealer so I ordered it, but they rang me soon after to say it was no longer available.
I have found it on the internet in Lithuania & Slovakia but with carriage included it would cost £20-25 which is insane for a single bolt.
I've just bought a cheap s/h master cylinder and reservoir off eBay with the bolt included for well under that, so it's sorted :mrgreen: .
Am feeling a lot more confident now about doing the job , thanks again :) .
 

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silverbug said:
Thanks that's really useful info , I'm going to get one of those Sealey gizmos you mention , I do have an Ezibleed but the Sealey looks much better.
It is odd about the reservoir bolt (1J2 611 353) , I was given a price this morning at my local VW main dealer so I ordered it, but they rang me soon after to say it was no longer available.
I have found it on the internet in Lithuania & Slovakia but with carriage included it would cost £20-25 which is insane for a single bolt.
I've just bought a cheap s/h master cylinder and reservoir off eBay with the bolt included for well under that, so it's sorted :mrgreen: .
Am feeling a lot more confident now about doing the job , thanks again :) .
As I mentioned in my thread when removing the reservoir try to avoid accidentally pulling the rubber clutch fluid supply hose away from the bulkhead hard pipe - its well hidden behind the aluminium heat shield which needs to come off to re-attach/clip - that's a real faff!

DC
 

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Discussion Starter · #13 ·
DC240S said:
As I mentioned in my thread when removing the reservoir try to avoid accidentally pulling the rubber clutch fluid supply hose away from the bulkhead hard pipe - its well hidden behind the aluminium heat shield which needs to come off to re-attach/clip - that's a real faff!

DC
I shall definitely take great care , thanks!
 

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Discussion Starter · #14 ·
Well can't fault Stafford Audi , ordered sensors very late on Monday night and they arrived this morning 8) .
Nice fresh stock too, these ATE sensors are a dark gun-metal colour, nothing like the silver-coloured supposedly OEM ones on eBay......
Just need to find time to do them now ......
 

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Discussion Starter · #16 ·
DC240S said:
Nice! Will be very satisfying when completed
Definitely, I think the fault has been there ever since I purchased the car in February as VCDS threw up a faulty brake light switch code (since replaced) which I now think was a manifestation of the pressure sensors beginning to play up.
There doesn't seem to be any logic to when the ESP light will come on now , it did appear to get worse on really hot days but now it seems random.
The sensor(s) gave wild pressure readings the first time I checked measuring block 5 with VCDS but after a long journey yesterday with an extremely hot engine bay (and no ESP light) the sensors tested fine :roll: .
Time will tell if this really sorts out the ESP light issue but I'm quite confident it will as at least one of the current brake pressure sensors is dodgy.
 

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Discussion Starter · #17 ·
I've got all the parts and tools required now to do the job, plan is to change the sensors early next week.
Seeing as how access is so tight in there, I plan on removing the reservoir as per DC240S's thread.....

DC240S; can I pick your brains with regard to the hydraulics please?
Did you just whip off the old sensors and screw the new ones in, or did you try and fill the new sensors with a drop of brake fluid prior to putting them in (there seems to be enough room to get fluid in there..)?
When it comes to bleeding what order did you do it in?
I'm guessing :
Master cylinder bleed nipples
Front left calliper
Right front caliper
Clutch

Lastly , I gather from your thread that you didn't need to do an ABS pump bleed?
I'm really hoping that I don't either!

Thanks!
 

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silverbug said:
I've got all the parts and tools required now to do the job, plan is to change the sensors early next week.
Seeing as how access is so tight in there, I plan on removing the reservoir as per DC240S's thread.....

DC240S; can I pick your brains with regard to the hydraulics please?
Did you just whip off the old sensors and screw the new ones in, or did you try and fill the new sensors with a drop of brake fluid prior to putting them in (there seems to be enough room to get fluid in there..)?
When it comes to bleeding what order did you do it in?
I'm guessing :
Master cylinder bleed nipples
Front left calliper
Right front caliper
Clutch

Lastly , I gather from your thread that you didn't need to do an ABS pump bleed?
I'm really hoping that I don't either!

Thanks!
After syringing as much fluid from the master cylinder as possible (with workshop tissue underneath for spillage/dripping), I just removed old sensors and replaced with new.
Yes - bled master cylinder first - then clutch IIRC then callipers. Didn't need to bleed ABS as this remained a closed circuit during process. To 100% remove old fluid and any air suspected in the system - yes bleed the ABS.

Thats as I understand/did - I may be corrected.
 

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Discussion Starter · #19 ·
DC240S said:
After syringing as much fluid from the master cylinder as possible (with workshop tissue underneath for spillage/dripping), I just removed old sensors and replaced with new.
Yes - bled master cylinder first - then clutch IIRC then callipers. Didn't need to bleed ABS as this remained a closed circuit during process. To 100% remove old fluid and any air suspected in the system - yes bleed the ABS.

Thats as I understand/did - I may be corrected.
Great stuff , thanks for the extra details ! :) .
 

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Discussion Starter · #20 ·
Well I've come to an impasse :( .
I just can't remove this cradle thing to get at the sensors , I've managed to wiggle it free of a stud so it moves side to side an inch or two but there's no way I can get my hands or any tools in there as it is :cry: .
The screw holding the reservoir on is on this side too so until this cradle is out of the way I'm stuck.
I did manage to half unclip the lid on this thing then decided that it didn't serve any purpose and so replaced it, fearful of breaking those pipes I've downed my tools :( .
Does it undo from below?
I haven't removed the engine under tray because I was hoping not to have to go to all the faff .
 

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