Brake Servo Replacement 4.2tdi

[manca]

Hi folks
Anyone had this done. I've got an issue where the brake boost isn't working following engine start up. First noticed it in a car park, and yesterday on the driveway. As soon as I'm off and moving everything is fine. Local indie had car today and says vacuum draw and pressure seem okay although they dont have data for a 2010 engine so basing it off other cars.... but the servo is slow to react and they suggest as point one needs replacing. Quoting £1500 as a starting point saying upper limit unknown as multiple parts including both calipers may need replacing following brake bleeding and strip down as they are prone to damage.

[ainarssems]

Sorry, no experience changing it on D4 but seems a bit suspicious that it works when you start moving. I would think it's not enough vacuum in idle and when you start moving and rpm increase you have more vacuum and it works, which would mean weak pump or vacuum leak somewhere, of course could be a leak inside servo too. Should do a vacuum leak test on whole system and individual parts first before committing to replace servo.

[manca]

Thanks for replying ainarssems.

That gives me a bit of hope. I'm off to collect the car later today so I'll ask some questions

[manca]

Picked the car up this afternoon, the Master Tech who worked on my car yesterday wasn't in and no one else to speak to me so left with car. Started engine put it into D rolled forwards, pressed brake, no servo. Lever into N blipped throttle to 2k rpm for a couple of seconds, repeated roll forward and servo worked. Released brake pedal and tried again, no servo. Headed gingerly down the road 10-15 mph.... servo working for one brake push but not subsequent when pumping brakes. This got better the further I went until at least 3 brake pushes kept servo assistance even if I didn't touch accelerator. Out onto main road and normal driving for about half a mile. Then in a traffic Jam for 15 mins, where almost no accelerator just roll forward a bit and brake repeatedly. Finally free of the traffic there was 2 miles of mixed driving up to and including a mile or so at 40ish mph. Throughout brakes worked with servo as I would expect. Got home parked up. Tried rolling forward and pumping brakes. First couple of presses had servo and then pedal got firmer and firmer with no servo assistance.

[manca]

So car was booked into Audi Walton on Monday as Main Dealer was 20% cheaper than the Indie quote I had. Got a message this morning advising my appointment has been cancelled as the part is no longer available from the brand. Happy days

[sarg]

Parts NLA for D4s FFS

This is why I will never buy another VAG product again

[steamship]

Quoting £1500 as a starting point saying upper limit unknown as multiple parts including both calipers may need replacing following brake bleeding and strip down as they are prone to damage.

Can't understand how callipers would need replacing because of damage due to a failed/failing brake servo.

the part is no longer available from the brand.

Just to confirm, your title states 'Brake Servo'. For a 2010 model, the original part number is 8T0612107, which was dropped December 2018. However, there is a superseded part, which is part number 4H0612107A, and is highly unlikely to be NLA yet.

[manca]

Hi Steamship thanks for that info. I've sent it into the main dealer will await a reply. The calipers issue was because Indie garage advised the bleed nipples on the calipers are notoriously prone to break and if that happened new calipers would be required

[steamship]

The calipers issue was because Indie garage advised the bleed nipples on the calipers are notoriously prone to break and if that happened new calipers would be required

OK, that explains it.

[manca]

Car in Main Dealers this morning. Confirmed the revised part number is discontinued so if my servo needs replacing Audi wont be doing it.

[steamship]

Confirmed the revised part number is discontinued so if my servo needs replacing Audi wont be doing it.

That is absolutely crazy. Produce a part for 5 years and then stop! I can find a few sites in the US that have it, but none in the UK or Europe. If you need to source one from the US, I'd go with FCP Euro as they have a lifetime warranty.

Dean (Spanker) is good at finding German sites with stock.

[manca]

Thanks for the info again steamship. Yep just had a call from the dealer. They don't know what the issue is, there are no fault codes, the car is reporting no issues. So I'm not sure where I go next. They say they can start stripping it down at £222 an hour labour and see what they find. Obviously if they get to the servo they won't repair it and then I can pay them to put it back together and go somewhere else to get it fixed..... not.

Losing the will if I'm honest

[steamship]

ainarssems back in post #2 hinted at a possible vacuum leak. Do you know if they investigated that possibility?

Looking at the 4.2tdi, there is a vacuum pipe (#2 & 3 in the first image) with a non-return valve from the brake reservoir to the mechanical vacuum pump. Cars that have stop/start have a pressure sensor on them (PR code: 7L8).

There is also the vacuum pump itself (second image), although I can't find a decent image of where it is located on your engine. The following video shows what it looks like, but this was on a FSI engine. It might be worth checking those areas for vacuum leaks.

https://www.youtube.com/watch?v=EvfFk3ZJP6o

[manca]

Typed out a rambling response Sean but it didn't post then I couldn't log in.
Anyway more concise than the original.....

Thank you for the info above.
I suspect the Main Dealer simply plugged the car in to diagnostics and then phoned me and told me they didn't know what the issue was.
The Indies Master Tech last month told me they checked the vacuum and although there was no manufacturer specification for the measure on early cars the draw seemed in line with cars that are operating normally. He said when he exhausted the pressure the servo was then slow to react.

[manca]

Off to retrieve my car now.

I've booked it in with Audivwcs in Harrow. Was introduced to them years ago by Marcin when I had my D3 but haven't been back since I moved. They were great back then so fingers crossed

[manca]

Car into Audivwcs yesterday afternoon. Problem diagnosed and explained this morning.

As suggested on this thread the smoking gun isnt the NLA servo. I need a new water pump. It has leaked coolant into a vacuum pipe. They could see the pink crystals partially blocking the pipe. Cleaned the pipe out and all operates as normal. Water pump on order and car back on Monday. They said they've never seen it before and it took some working out, hence they didn't get back to me yesterday as intended. I appreciate everyone's input thank you

[steamship]

I need a new water pump. It has leaked coolant into a vacuum pipe. They could see the pink crystals partially blocking the pipe. Cleaned the pipe out and all operates as normal.

Well that particular scenario wasn't expected, but great that they found it.