Vacuum at idle?

OzzyLime · 11-16-2011, 08:28 AM

I will skip the boring details

I have vag-com, trying to trace a code and determine if I have a giant vacuum leak or a bad brake booster. What should vacuum be at idle?

Prospeeder · 11-25-2011, 07:03 AM

vacuum should be 17-21 inches at idle. A vacuum leak is not going to make that number lower. If the leak WAS bas enough to make it lower, i garentee the engine wont run. Use a can of brake cleaner while its running spray around potential leak points, and if there is one, the engine will rev up or sputter when its sprayed in the offending spot. Whats the code? Fuel trim lean? MAF sensors are common for lean codes.

OzzyLime · 11-25-2011, 11:45 AM

It is throwing a electric brake vacuum pump - mechanical failure code. Brakes don't work unless you stand on them, and at WOT check engine flashes (misfire).

Prospeeder · 12-02-2011, 06:27 PM

Well then you have a bad booster, bad booster check valve, or bad brake vacuum assist pump thats dead. Most likley the booster itself, i have replace several of them

OzzyLime · 12-03-2011, 06:38 AM

Quote:

Originally Posted by Prospeeder

Well then you have a bad booster, bad booster check valve, or bad brake vacuum assist pump thats dead. Most likley the booster itself, i have replace several of them

Is the booster check valve in the long Y pipe that plugs into the port on the firewall? That may make sense since it is a new one off ebay.

Prospeeder · 12-03-2011, 08:22 PM

yes. its the thing that plugs into the fire wall. Thats the check valve. Sounds like the diaphragm in the booster split. That or the oring between the master and the booster somehow is leaking

11-25-2011, 11:45 AM	#3
OzzyLime AudiWorld Member Garage is empty, add now Join Date: Apr 2011 Location: UV 1 Million Florida Posts: 291	It is throwing a electric brake vacuum pump - mechanical failure code. Brakes don't work unless you stand on them, and at WOT check engine flashes (misfire). __________________ 2001 A6 2.8 - motor replaced after valves vs. pistons 1997 A4 1.8T QUATTRO 5SPD - Projekt kar 1997 A4 1.8T FWD AUTO - bought for less than the price of a decent laptop. Gave to sister [ Vorsprung durch Technik ]

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11-25-2011, 07:03 AM	#2
Prospeeder AudiWorld Senior Member Garage is empty, add now Join Date: Aug 2011 Posts: 837	vacuum should be 17-21 inches at idle. A vacuum leak is not going to make that number lower. If the leak WAS bas enough to make it lower, i garentee the engine wont run. Use a can of brake cleaner while its running spray around potential leak points, and if there is one, the engine will rev up or sputter when its sprayed in the offending spot. Whats the code? Fuel trim lean? MAF sensors are common for lean codes.

12-02-2011, 06:27 PM	#4
Prospeeder AudiWorld Senior Member Garage is empty, add now Join Date: Aug 2011 Posts: 837	Well then you have a bad booster, bad booster check valve, or bad brake vacuum assist pump thats dead. Most likley the booster itself, i have replace several of them

12-03-2011, 08:22 PM	#6
Prospeeder AudiWorld Senior Member Garage is empty, add now Join Date: Aug 2011 Posts: 837	yes. its the thing that plugs into the fire wall. Thats the check valve. Sounds like the diaphragm in the booster split. That or the oring between the master and the booster somehow is leaking

12-03-2011, 08:22 PM
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