Hi,

I have a 2001 Audi A4 1.8T Quattro. The car has new front brakes and rotors, 10000 miles on the rear brakes with turned rotors, and Audi changed the brake fluid about a year ago.

The problem? For about a year now, when I back out of my garage, parking spot, etc., I have to step on the brake pedal as hard as I can to slow or stop the car. This usually only occurs after the car has been sitting for several hours. Since this has been going on for about a year, I figured out that if the car is in neutral, the brakes work perfectly. In other words, if feels like brake assist is actually working. The brake pedal feels like any other car including when I purchased the car when in neutral. Once I put it in gear, the brake pedal feels like something is not allowing it to place pressure on the pads, ABS issue?

What have I done to fix the issue? Audi has seen the car about 8 times in the last year and can't figure it out. They replaced all of the vacuum lines and a vacuum junction to the master cylinder. They also replaced the brake fluid and bleed the system. They refuse to change out the master cylinder because the pressure gauge indicates normal (within limits) pressure. They also increased the idle speed of the engine, I guess to create more vacuum pressure.

Local mechanic? I took it to a local mechanic and they replaced the front pads and rotors, but it feels worse now. They were suppose to figure out this issue, but forgot. I'm taking the car back for review, but in the meantime, what are all these guys missing? What are all of the things they need to investigate to solve this issue?

By the way, once the car is moving, brake pedal pressure and braking feel okay. Not 100%, but maybe about 85%.

Thanks!

GP

 

If your idleing above 850 rpm it's like stepping on the gas. You'll have to overcome this
with heavy pressure on the brakes.

 

I have to get in the car to check the RPM after start. Usually when I step on the brake pedal it feels like there's pressure on the pedal. When I place the shifter in reverse the brake pedal drops toward the floor.

Are you also suggesting that Audi increasing the idle speed could create less vacuum or pressure for the master cylinder?

Thanks,

GP

 

Wouldn't the above quote refer to an automatic transmission? It sounds like the car is a manual so the idle speed wouldn't effect it.


When you have to press hard on the brakes, if you hold contant pressure on the brake pedal, does the pedal creep down toward the floor, or does it stay up where it should be. If at any time you can push your brake pedal to the floor, your master cylinder is failing and needs to be replaced.

If the brake pedal feels firm, but is actually VERY firm and hard to push, then I would suspect its the brake assist.


What tranny do you have? How many miles on the car?

 

Increasing the idle speed will make it harder to stop the car.

This is a typical symptom of a slow leak in the brake vacuum assist. When the car sits for several hours, the vacuum assist leaks and you have no boost for the first 30 seconds or so. Tell them to listen to the symptoms rather than their instruments. The reason they can't find the problem is that they are ignoring what you are telling them.

doctors sometimes do the same thing.

 

I have an automatic transmission with about 89000 miles. My car was idling around 1100 RPM, then several seconds later 800 RPM before I put it in reverse.

When the problem occurs, I have to push on the brake pedal very hard to stop the car. It certainly feels like the brake pedal sinks toward the floor versus staying up where it should be. It also feels like I have only two options to stop the car, either brakes on or off. Once the car is moving forward, the brake system feels okay. When it's hot outside the problem is worse. If it's cold, the problem just about goes away, except for the first start of the day.

Brake assist? Is the brake master cylinder responsible for brake assist? Or is there another system for brake assist?

Thanks for help everyone!

GP

 

The big black thing that looks like two pie plates.

 

Well I think you were just looking for ideas on what the problem was so you have have the shop fix it. Its probably the master cylinder or brake assist. My money is on the master cylinder.

Make the shop replace it. I don't care what the pressure guage says. If its not in one of those two systems (considering all of the other stuff they did to the car to try to fix it), I don't know where else it could be.

After you get it to the shop, post back here on whether it fixed the problem.

 

UPDATE!

Local mechanic found the following:

* Engine has blowby from block, therefore not creating enough vacuum pressure to the brake assist. Cold start produced 8" of pressure.

Audi mechanic found the following today:

* This is a known problem with the 2001 A4 with the 1.8T Quattro automatic tiptronic transmission engine. This might be a recent Audi discovery. Anyway, they installed an "Electronic Vacuum Pump Retrofit Kit". He tested the vehicle prior to the retrofit and he stated that it felt like the car had no brakes after the first start of the day. With the kit, the car has normal assist. I'll let everyone know how it feels in the morning after the car sits overnight. The mechanic also stated that there's nothing wrong with the engine. He also stated that every model after 2001 has an electronic vacuum pump installed.

If it helps anyone, they covered it under the CPO (certified preowned warranty). If the car is not under warranty, they told me that the kit sells for $421.00. Don't know if that price includes labor.

Thanks for the help guys,

GP