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OK, I'm not entirely sure what you are going to do with this information, because we all take brakes for granted, but I thought I'd better let you know what happened to me.

For those who don't know, the brake servo needs suction to provide assistance to the brake pedal force and it gets the suction from the intake manifold, via a rubber pipe.

My rubber pipe failed with no warning when approaching a roundabout... thankfully I was able to avoid the vehicle infront by moving into the other lane, but this sudden failure took me by surprise. The brake pedal went firm, and it took a hell of a lot of standing on the pedal to get anywhere near a small fraction of normal brake deceleration.
Other symptoms included a very rough idle sometimes rising to 2k RPM and a suction noise coming from front of engine (both caused by the unmetered air being sucked into the intake manifold).

I drove very sedately to the nearest Audi garage where all associated pipes and connectors were replaced. The intake manifold had to be removed to get access to the pipes.
So this might not change your driving habits, but it certainly made me think twice about last-minute braking!
Has anyone ever had such a failure on any make of car before?
This must be quite rare? (At least I hope so).

I know of one that has had that happen..

Did the car have a FASH?? If so I would hit the roof with them as they are supposed to check condition of things like vacuum hoses.

Any rubber component is liable to degrade with age, especially in the heat and damp of an engine bay on cars the age ours are now reaching.

Dave

We've done a few now , The brake booster valve fall's apart ....It's a pain to fit but it's only a cheap part.

grizz wrote:We've done a few now , The brake booster valve fall's apart ....It's a pain to fit but it's only a cheap part.

Grizz is there a way of testing or does the valve just let go?.. Any symptoms of impending failure etc.. ta

High tickover .boost leak ..

Resurrection of an old thread, but exactly the same thing happened to me yesterday. On the motorway trundling along in the outside lane, approaching my exit and F***ing Hell!! Brake pedal rock hard and with both feet managed to slow it enough not to hit anything. Sure enough lifted the bonnet and I can hear near the front of the engine what sounds like air being sucked in. Typically it was only the day before that I had rung Grizz to book it in for engine and gearbox service.
So the question is guys, is there an easy way to sort something so I can drive the 150 miles up to unit 20? I could drive slowly, but I am worried what that vacuum leak would do to the engine. Any advice would be greatly appreciated. Thanks

Probably best to get it trailered.

Try www.shiply.com Used them in the past quite a few times, around £1 per mile should be the sweet spot for bids I reckon.

Heard of this from a few folks, dreaded vacuum line fail leading to no braking, not good...

Daveperc wrote:Did the car have a FASH?? If so I would hit the roof with them as they are supposed to check condition of things like vacuum hoses.

Any rubber component is liable to degrade with age, especially in the heat and damp of an engine bay on cars the age ours are now reaching.

Dave

This is not something which can be checked without doing a lot of work to remove the manifold. It may be possible to stress-test to check the operation of the valve with a higher suction, so that if it was going to fail it would fail during the test. It's not going to be fun trying to stop 2 tons from 70mph with no servo assist.

Update - haven't moved the car for a week or so, today took it to the local tyre depot very carefully. When I started it to drive back - servo is working again. So I'm thinking what the hell is going on. Need to get it up to Grizz to have a look at, but concerned it has now become an intermittent fault and may not be so easy to trace. So Gentlemen, any ideas what could cause this????

Wow, Should this be something that Audi need to look at. I had my 1998 A3 recalled for brake vacuum lines failing. They replaced some pipes Under the recall for free and the car was about 12 years old at the time. I use my rs6 for family holiday so I think I need this checking. Have owners contacted Audi?

Ed

Drummerman wrote:Update - haven't moved the car for a week or so, today took it to the local tyre depot very carefully. When I started it to drive back - servo is working again. So I'm thinking what the hell is going on. Need to get it up to Grizz to have a look at, but concerned it has now become an intermittent fault and may not be so easy to trace. So Gentlemen, any ideas what could cause this????

I'm guessing its the £5 plastic valve under the intake manifold, it's sticky.