Brake pedal goes hard & Turbo Actuator fault

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Posts: 2
Joined: Fri Jun 10, 2011 9:58 pm
Passat model: B8

Brake pedal goes hard & Turbo Actuator fault

Post by humbucker1960 » Wed Jul 31, 2019 12:11 pm

Sorry for the long post.
I have had my Passat B8 2.0L GT Estate for over a year now.
In January the glow plug light came on shortly after starting the car up in the morning and went into limp mode.
I turned the ignition off and re sarted the car and all was ok. It has done this about 3 times and in March it went to the VW main dealer for a service at 88000 miles.
They told me it was the turbo actuator that was faulty at a cost of over £400 to replace, but they also kindly told me it might be the Turbo.
As it only happened a few times and only on startup I declined the repair work.
In April after starting the car and driving nearly a half a mile I put my foot on the brakes and the pedal was solid, I nearly had a heart attack.
This happened about 3 more times, some times straight away after setting off and sometimes a short distance after within a half mile.
I think both faults are related
The brakes always work in the morning for the first few presses of the pedal so I persume there is a vacume held in the system,
its always in the morning and never happened at any other time.
In the morning I now always pump the brake pedal until its hard then start the car, with light pressure on the brake pedal it takes any ware between a second and the longest was 30 seconds before the pedal sinks,
after the pedal has sunk its fine and never gives me a problem for the rest of the day.
Both faults only ocurr in the morning after startup.
I think its a intermittant vacume fault, has anyone any ideas or know of a vacume diagram for this car then I may be able to find the culprit.
One thing that realy has me frustrated is the car can tell me me many things from the fault lights and display on the dashboard but it cant tell me there are no brakes, worrying that is.
Many thanks.

Posts: 419
Joined: Wed Mar 30, 2011 4:53 pm
Passat model: B8 GT DSG 230bhp
Location: Loch Lomond

Re: Brake pedal goes hard & Turbo Actuator fault

Post by smilie121 » Sat Aug 10, 2019 10:37 am

You may have 2 unrelated faults.

With that mileage have you had the brake fluid renewed?

I had a similar brake pedal issue with an older passat but it presented no warning lights. Sometimes the pedal just felt like it was travelling too far. I renewed brake fluid and bled all calipers and was as good as new.

Brake fluid absorbs moisture over time so it does degrade.

Worth a shot if you can do it yourself or get garage to do it.

Not experienced enough to comment on turbo / limp mode. I did the Mr Muscle trick when my last passat was going into limp mode. I tried it before heading to a garage after reading forums.

It only went into limp mode if i booted it hard. Would resolve if i turned off for a minute and started again.

Posts: 739
Joined: Sun Dec 01, 2013 12:15 am
Passat model: b5.5 4motion est
Location: Cambridge

Re: Brake pedal goes hard & Turbo Actuator fault

Post by passartist » Sat Aug 10, 2019 11:38 pm

any chance the vacuum system is shared from brakes to the turbo and it has a leak? Would seem to make sense.

Posts: 2
Joined: Fri Jun 10, 2011 9:58 pm
Passat model: B8

Re: Brake pedal goes hard & Turbo Actuator fault

Post by humbucker1960 » Mon Aug 12, 2019 8:54 pm

Hi Smilie121,
The car is only 4 years old and has had all the services done at the main agent so if it needed changing then it would have been done at the service. The brake fluid is clean and the brakes are fine except ocasionly after the first start in the morning when I have to wait for the pedal to sink. I have ordered a N75 valve from a breaker to see if its that.

Both the brake servo and the turbo actuator have vacume pipes, I dont think its a leak as the brake pedal is not hard before starting the car,
I can pump it about 4 to 5 times before it goes hard.
I have ordered a N75 valve off ebay to see it if its that. I definatly think its something to do with the vacume circuit and I think its some sort of a valve thats playing up. Hopefully I will find it but could do with the correct vacume diagram for it.

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