Hi all,
After struggling with a brake vacuum issue on an 01 B5, I finally found the solution. The issue was that I had low vacuum on cold engine start-up (FYI - in Denver so altitude reduces vacuum 1 inch per 2000 feet - this equated to a 3 inch drop for me). Once warmed up, I had a nice 21 inches of vacuum. After testing and replacing everything with no success, I came to the conclusion that VW had a reason for installing the brake vacuum pump on the B5.5. So I did the same to the B5 and now everything is fine. Here is how I did this...
Parts required (to make things easy):
Install the vacuum pump
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Create the Trigger to Turn on the Vacuum Pump
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Route the Lines
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Install the Vacuum Sensor
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After struggling with a brake vacuum issue on an 01 B5, I finally found the solution. The issue was that I had low vacuum on cold engine start-up (FYI - in Denver so altitude reduces vacuum 1 inch per 2000 feet - this equated to a 3 inch drop for me). Once warmed up, I had a nice 21 inches of vacuum. After testing and replacing everything with no success, I came to the conclusion that VW had a reason for installing the brake vacuum pump on the B5.5. So I did the same to the B5 and now everything is fine. Here is how I did this...
Parts required (to make things easy):
- Brake vacuum pump from a B5.5 (note: my donor car for all parts was a 2001 B5.5) - part number 8E0-927-317A - I suspect any VW brake vaccum pump will work
- Brake vacuum sensor and hoses - the hose between the firewall and the brake booster - 4B1-611-931AC
- Brake vacuum hose between the brake vacuum pump and the firewall - 4B0-611-931BR - definitely need this one - the V6 line is different
- Brake vacuum pump / ABS bracket - 4B0-614-119Q
- Brake vaccum pump / ABS bracket cover - 3B0-422-569A
- Original wires from the wiring harness cut out from donor vehicle
- Vacuum switch (I purchased mine from DesignFlex -www.designflexswitches.com - switch PSF109S)
- This has a design life of over 10 million cycles - should be enough!
- Extra wire for extensions and wire connectors
- T-fitting - 1/2" x 1/2" x 1/4"
- 1/4" hose - approximately 2 feet
Install the vacuum pump
- Lift the coolant reservoir out of the way - three philips head screws
- Disconnect the electrical connector from underneath so it can swing out of the way better
- Replace the brake vacuum pump / ABS bracket
- There are three 6mm bolts (10mm hex head)
- Remove the one bracket that holds the vacuum line directly beside the bracket - one 6mm bolt (10mm hex head)
- Loosen the two 8mm nuts (13mm hex head) that hold the ABS module to the bracket
- Lift the ABS unit slightly and pull the old bracket out by pulling down and towards the middle of the engine
- Install new pump in reverse order
- Install brake vacuum pump
- Push in place
- Push two clips in to secure
- NOTE: Now this looks just like the B5.5; the following picture shows the installed vacuum pump
Create the Trigger to Turn on the Vacuum Pump
- On the B5.5, the ECU triggers the vacuum pump; this is not an option on the B5 since the ECU is unaware of this pump; so we add our own sensor
- Splice into the brake hose
- The B5.5 brake hose between the firewall and the brake booster already has a vacuum sensor inline
- You cannot use this since the ECU does not know how to interpret its signals
- Remove the original sensor from the hose
- Install the T-fitting - the one I used was from Lowes, exact fit
- Install the 1/4" hose on the T-fitting and route it under the master cylinder towards the ECU
- Here is a pic of the T-fitting installed
Route the Lines
- I wanted everything to be inside the car rather than exposed to the elements in the engine compartment
- So the vacuum switch and all electricals and routed to the passenger compartment
- Notice in between the ECM and brake booster there is a hole with a sealed grommet covering it
- I used this as my access point to route the vacuum line and electrical wires
- Cut out the middle dimple - that allows sufficient room to route the hose and wires through
- Here is a picture on the completed job with black silicone added to ensure it is waterproof; notice in the lower right you see wiring that was added - will cover this shortly
Install the Vacuum Sensor
- The Sensor I used had both a "normally open" and a "normally closed" connection
- This sensor simply opens/closes a circuit when a specified vacuum in attained
- Here are two pictures of the sensor I used
- I used the "normally open" connection - will cover wiring in the next section
- Set the switch to the desired vacuum
- Notice in the middle of the vacuum connection there is an allen head screw
- Using a 5/32" allen wrench you can adjust when this switch opens/closes
- I adjusted the switch to close at 20 inches - this means the switch will cause the pump to run until it reaches 20 inches of vacuum at the brake booster
- This switch has a 25% deadband, which means the switch opens at 25% reduction from the setting, hence, the switch will turn the vacuum pump on if the vacuum drops below 16 inches
- Wiring was pretty simple - here is a picture from Bentley of the original wiring for the B5.5; it is marked up to denote the wiring I did
- The brake pressure sensor was eliminated so those wires are eliminated
- Vacuum Pump
- The ground wire is routed to a ground near the fuse box
- The juice comes from the original brake vacuum booster relay
- Brake Vacuum Pump Relay
- Relay Activation juice (4) - routed to a "key on" hotwire in fuse box
- Relay Activation ground (6) - from vacuum pressure switch
- Pass through juice (2) - routed to a "key on" hotwire in fuse box
- Output juice (8) - goes to vacuum pressure pump
- Vacuum Switch (not pictured)
- Source ground - routed to a ground near the fuse box
- Output ground (normally open) - routed to brake vacuum pump relay
- NOTE: On a connecting page in the wiring diagrams, the juice wire for the relay comes from a safety fuse; I kept this from the original wiring
- Route the wiring
- The wiring from the pump is rerouted; instead of going towards the middle of car into the wire harness, it routes to the outside of the car and goes into the cowl by going under the cowl weatherstrip all the way on the left of the car - there is a one inch section that is open
- Then heads into the passenger compartment through the hole noted earlier; here is a refresher photo ( its in between the ECM and brake booster
- Hook up the ground and juice sources
- Juice
- The juice relay activation and pass through were hook together so that the safety fuse could be shared for both of them
- The safety fuse was clipped onto the fuse box
- This juice wire was connected to the fuse box on a post that is constantly hot when the key is on or engine running
- There were two posts that were hot when the key was on but only one stayed hot when the engine was running
- This was the post closet to the outside of the car (see photo)
- Ground
- Both ground wires were routed to the post right by the fuse box with a 6mm (10mm hex head) cap nut
- Juice
- Clip the relay into the fuse box
- The original location for the B5.5 is location 10
- Hang the vacuum switch
- I chose to hang it on the bracket just above the steering column
- Connect the vacuum line to the switch
- I used tie straps to attach it to this bracket; this picture may be confusing, remember you are laying on your back in the car looking UP at the steering column
- Install brake vacuum pump / ABS cover
- The brake vacuum pump will run immediately when the key is turned on to start creating vacuum if the vacuum sensor senses less than 16 inches of vacuum
- The pump will run until 20 inches of vacuum are achieved
- At start up, I have good brakes!
