What was Audi thinking on the brake booster and vacuum line set up on the 2001.5 and up? (long)
10-09-2004, 04:49 PM
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What was Audi thinking on the brake booster and vacuum line set up on the 2001.5 and up? (long)
Several months ago while I was pouncing on a C5 Vette, I noticed a severe drop off in power and a quick following surge. I thought to myself at first, great time for a new MAF. Then I hooked it up to the VAG-com, and no faults other than the usual o2 sensor. I was perplexed.
I started noticing the drop and surge more and more and under full boost. Could not figure it out for the life of me. Next thing I know, I lay on the throttle, the boost is hitting 20psi, then boom, complete loss of pressure and the car is running on only engine power, but still with full boost.
All of a sudden, at the light, my car is shaking and hissing like crazy, and even better NO POWER TO THE BRAKES. Hitting the brake to stop the car was like trying to pull the reigns on an Elephant to stop, you really see how heavy our car actually is. I get the car to an office building parking lot. I pop the hood, a noticed the brake booster line completely disconnected from the vacuum lines running from the intake manifold. After 3 hours of trying to get a damn flat bed, who ultimately arrived with no 2x4s, even though I had requested trying to convince me that he does not need one to get my car on the flatbed, until I finally told him I was an attorney(LOL), I placed the brake booster line into the vacuum line, hoping the suction would hold it in place. I popped the clutch and rolled 1.5 miles home at 10mph with the tow truck following with its lights. 4 hours later we got home and I sealed the brake booster line back into the vacuum line with friggen super glue.
The moral of the story is that amazingly enough, the brake booster line does not screw in, click in, clamp on, nada, it is just (and from the factory) placed onto the vacuum line with adhesive. I guess they figured the suction would keep it in after the adhesive dissipates. Well, two days ago, it blew on me again, same type symptoms, but more like a consistent drop in power rather than drop and then surge. This time, I just thought that the car was running crappy because it was choking on the 2000 degree weather in South Florida.
We changed the configuration to run a line direct from the intake manifold to the brake connection in the firewall, similar to the 2000 and 2001 setup. What I could not believe is that there is that the line running from the intake manifold has four outputs, but only one is used by the brake booster line. The rest have to be plugged from running into the atmosphere otherwise vacuum is compromised and boost is lost to the wheels. Something about emmissions? But, what were they thinking? Power to the brakes is important, right? I ain't driving no damn 1500 lb fiero. If that line blows, there goes your power brakes. Also, earlier than 2001.5 models have the brake booster line hooked directly to the intake manifold, not connected to another line with 4 outputs, only one of which is used by the seperate brake booster line. Now before anyone yells to me "aftermarket brakes," this happened the first time while the stock brakes are on.
This happen to anyone else? Or am I the only lucky one?
I started noticing the drop and surge more and more and under full boost. Could not figure it out for the life of me. Next thing I know, I lay on the throttle, the boost is hitting 20psi, then boom, complete loss of pressure and the car is running on only engine power, but still with full boost.
All of a sudden, at the light, my car is shaking and hissing like crazy, and even better NO POWER TO THE BRAKES. Hitting the brake to stop the car was like trying to pull the reigns on an Elephant to stop, you really see how heavy our car actually is. I get the car to an office building parking lot. I pop the hood, a noticed the brake booster line completely disconnected from the vacuum lines running from the intake manifold. After 3 hours of trying to get a damn flat bed, who ultimately arrived with no 2x4s, even though I had requested trying to convince me that he does not need one to get my car on the flatbed, until I finally told him I was an attorney(LOL), I placed the brake booster line into the vacuum line, hoping the suction would hold it in place. I popped the clutch and rolled 1.5 miles home at 10mph with the tow truck following with its lights. 4 hours later we got home and I sealed the brake booster line back into the vacuum line with friggen super glue.
The moral of the story is that amazingly enough, the brake booster line does not screw in, click in, clamp on, nada, it is just (and from the factory) placed onto the vacuum line with adhesive. I guess they figured the suction would keep it in after the adhesive dissipates. Well, two days ago, it blew on me again, same type symptoms, but more like a consistent drop in power rather than drop and then surge. This time, I just thought that the car was running crappy because it was choking on the 2000 degree weather in South Florida.
We changed the configuration to run a line direct from the intake manifold to the brake connection in the firewall, similar to the 2000 and 2001 setup. What I could not believe is that there is that the line running from the intake manifold has four outputs, but only one is used by the brake booster line. The rest have to be plugged from running into the atmosphere otherwise vacuum is compromised and boost is lost to the wheels. Something about emmissions? But, what were they thinking? Power to the brakes is important, right? I ain't driving no damn 1500 lb fiero. If that line blows, there goes your power brakes. Also, earlier than 2001.5 models have the brake booster line hooked directly to the intake manifold, not connected to another line with 4 outputs, only one of which is used by the seperate brake booster line. Now before anyone yells to me "aftermarket brakes," this happened the first time while the stock brakes are on.
This happen to anyone else? Or am I the only lucky one?
10-09-2004, 07:31 PM
#5
same thing on my '01.5 A4 1.8T. thankfully, I had a bunch of zip ties that held it together
until I got a new one from the dealer for under $30. replaced it with a few new clamps in their parking lot.
03-10-2005, 06:59 PM
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Re: What was Audi thinking on the brake booster and vacuum line set up on the 2001.5 and up? (long)
I have a 2001.5 S4, and the exact same thing happened to me. I just bought the car used, and much to my horror, as I was coming around a very sharp freeway offramp at a high rate of speed, I noticed that I had no brakes!
After a little help from some guys in the forums, I was able to narrow down the problem - I had an Audi mechanic look at it and he told me I had "nothing wrong" with my braking system.
The problem is most noticeable when the engine is cold, although it happens from time to time after driving it hard. When I start the motor in the morning, it makes an extremely loud hissing sound. The engine idles low and it seems like the timing is off - it makes a throbbing noise, much like a detuned Z28 Camaro
Of course, the lovely problem of no brakes occurs for a mile or two, but when the engine warms up, the problem seems to subside temporarily.
I'm a total newbie when it comes to Audi engines - I've worked on Hondas a bit before, but I've no idea where to start looking under the hood - I don't suppose you happen to have a picture of the line in question?
Thanks for the story - good to know that others are having the same types of problems!
I also love your tach with the boost guage - where did you get it?
After a little help from some guys in the forums, I was able to narrow down the problem - I had an Audi mechanic look at it and he told me I had "nothing wrong" with my braking system.
The problem is most noticeable when the engine is cold, although it happens from time to time after driving it hard. When I start the motor in the morning, it makes an extremely loud hissing sound. The engine idles low and it seems like the timing is off - it makes a throbbing noise, much like a detuned Z28 Camaro
Of course, the lovely problem of no brakes occurs for a mile or two, but when the engine warms up, the problem seems to subside temporarily.I'm a total newbie when it comes to Audi engines - I've worked on Hondas a bit before, but I've no idea where to start looking under the hood - I don't suppose you happen to have a picture of the line in question?
Thanks for the story - good to know that others are having the same types of problems!
I also love your tach with the boost guage - where did you get it?
07-03-2010, 09:10 AM
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WOW i thought i was the only one.
im happy to hear that im not the only one with this problem! instead of super glue i taped it up with electrical tape. seemed to work for temporary use but i think i should try the super glue. i have to agee of what a poor design that is, u lose that hose and you lose your brakes! insanity! and i didnt know that it could affect the power also, i had noticed some loss here and there. anybody know how much that hose is to replace?
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07-03-2010, 02:58 PM
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Brake boosters on turbo cars almost always have a check valve in line so that the brake assist on the master cylinder only gets vacuum. If yours is blowing off under boost, you may want to replace and or add a check valve.
I'm sure the Audi engineers took the "vacuum only" idea into this design planning only on suction, never pressure to blow the connection.
I'm sure the Audi engineers took the "vacuum only" idea into this design planning only on suction, never pressure to blow the connection.
11-20-2010, 02:49 PM
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This happened to me recently... actually waiting for the part as we speak. Just to provide information, you can replace the 'pump' or the whole assembly:
078133701AD (Whole Assembly)
078133753A (Pump)
The 'pump' is attached to the hard vacuum lines by a shrinking process, as with most of the other check valves on the 2.7T. You can remove and install lines by heating up the section with something like a heat gun.
Oh, and you don't lose your brakes. You lose your vacuum assist, which in simple and non-technical terms, it takes a lot more foot force to stop, but your brakes still work and you can still stop.
078133701AD (Whole Assembly)
078133753A (Pump)
The 'pump' is attached to the hard vacuum lines by a shrinking process, as with most of the other check valves on the 2.7T. You can remove and install lines by heating up the section with something like a heat gun.
Oh, and you don't lose your brakes. You lose your vacuum assist, which in simple and non-technical terms, it takes a lot more foot force to stop, but your brakes still work and you can still stop.
11-21-2010, 07:15 PM
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Yes this happened to me while playing with a 911TT a few weeks ago. It's a guy that works in the same building I do.
I knew a hose had popped in the brake booster line almost immediately since this is not my first turbo car.
I drove the car home with the heaviest manual braking I have ever seen and found the offended busted plastic T fitting behind the intake manifold.
I have been building and flying R/C airplanes for years and am familiar with every grade, strength, thickness and drying time of cyanocrylate glue (super glue) made. I went to my fridge and picked out the medium gap filling replaced the fitting and ran a nice bead around the entire edge.
I let it dry all night.
I've been driving the car like a stole it for a month now since the repair.
I don't know why they chose this for an OEM installation, but it is easy to repair
.
I knew a hose had popped in the brake booster line almost immediately since this is not my first turbo car.
I drove the car home with the heaviest manual braking I have ever seen and found the offended busted plastic T fitting behind the intake manifold.
I have been building and flying R/C airplanes for years and am familiar with every grade, strength, thickness and drying time of cyanocrylate glue (super glue) made. I went to my fridge and picked out the medium gap filling replaced the fitting and ran a nice bead around the entire edge.
I let it dry all night.
I've been driving the car like a stole it for a month now since the repair.
I don't know why they chose this for an OEM installation, but it is easy to repair
.