BetaTDI has been having problems with his car and asked for a link on how to do this proceedure, one does not exist, so I am outlining the proceedure for future reference.
First of all this proceedure applies to all the passats, and the 97 and 98 Jettas, it does not apply to any of the NB's or Jettas and Golfs after 99 as they do not have a wastegate, they use the VNT 15 turbo.
A small discription of the system follows.
I believe the system functions like this.
Most wastegated Turbos operate off of vacuum, this system operates on pressure. The wastegate is normally open and diverting exhaust gasses all the time. To develop maximum boost the wastegate actuator diaphram is pressurized which shuts the diversion of exhaust gasses allowing them to drive the turbo. This would make it a failsafe system, if a component in the system develops a leak or obstruction the result is less total boost, and not excessive uncontrollable boost. The wastegate would fail to operate, and therefore the majority of exhaust gasses are diverted to the exhaust system, boost would be limited to around 9psi in this case at maximum load whereas normally it will peak at 15psi and settle to 13 continous.
The system is controlled by the ECU through a wastegate solonoid valve. Again to be failsafe the solonoid is set so that when it is off the pressure signal sent to the wastegate actuator is derived from the pre-turbo intake system of the engine. Very little pressure is applied and therefore boost is limited. When everything is working as it should, pressure supplied directly from the turbo is applied to the wastegate solonoid valve (hereafter refered to as the WSV) via the red hose, it attaches to the compressor side of the Turbo with a banjo fitting. The ECU sends a ground signal to the WSV to actuate it, this in turn allows the pressure from the red hose to flow to the blue hose. The blue hose is attached directly to the wastegate Actuator diaphram. This activates the actuator, closing the wastegate and allowing more boost pressure. When the ECU senses too much boost by means of the MAP sensor (located in the ECU, the signal is taken by hose off of the upper intercooler return line to the intake manifold)it removes the ground signal from the WSV and it vents the actuator diaphram to the intake via the black hose.
The WSV is located in the left firewall near the airbox. The problem as I percieve it is that the black hose is located near the PCV inlet of the intake. This area becomes very dirty if the PCV is connected on the engine. Some of this crud finds it's way into the WSV and maybe even the actuator itself. The valve becomes partially blocked which will not allow full pressure to the actuator. The sysmptoms of this will be, a code being tripped in the ECU where the specified boost the ECU is expecting to see is not what is actually availible, the actual boost pressure is to low, the code is listed as Manifold Absolute Pressure difference detected or intermittant. This will generally thow a CEL(check engine light) and power will be reduced until the ignition switch is cycled off and then on. This condition will normally occur under high boost demand, ie..going up hills, 5th gear and above 3000 rpms.
Failure of the WSV will cause this problem, as will leaks in the red or blue hoses, or the actuator diaphram at the turbo is ruptured, or there is a kink or obstruction in any of the hoses or obstruction in the valve.
The first order of business will be to bypass the PCV. Remove it from the intake port, plug the port and attach a PCV filter to the outlet port on the valve cover with a length of 3/4" hose. The comprehensive proceedure for this has been outlined by others.
Next, clean the intake elbow thouroughly especially in the area around the small black hose which exits off the intake elbow. remove this hose from the intake and the WSV and spray contact cleaner into the hose until it comes out clear, be sure to use a product that is not harmfull to rubber or platic, test it first on some ABS plastic, and on a small section of hose to make absolutely sure it's not going to eat your hoses up. Once you have cleaned the black hose, remove the Blue one and red one and do the same. The WSV is in a small rubber mount that pulls straight up to disconnect it from the mount. Remove it and clean it completely. I would recommend spraying the ports while actuating the valve, this would require rigging up a connection to 12vdc on the connector and cycling it while spraying cleaner into the ports. I would also recommend some compressed air that can be purchased from most electronic supply houses to blow out the lies and valve before reassembly. Make sure the banjo fitting at the turbo is clean, securely connected, none of the lines have kinks or holes, it may even be a better idea to replace the lines. A hand pump can be used to verify the diaphram actuator is functioning properly, 13 to 15 psi should open it completely. If it will not open, the diaphram is shot, this can be replaced as an assembly, it's bolted to the turbo on a bracket. Keep in mind that the wastegate itself could have crud preventing it from closing completely. To clean this would require the exhaust Downpipe be removed and it would have to be cleaned through the exhaust outlet of the turbo. I hope this helps. I would appreciate any corrections or suggestions anyone has.
[This message has been edited by valois (edited November 07, 2000).]
First of all this proceedure applies to all the passats, and the 97 and 98 Jettas, it does not apply to any of the NB's or Jettas and Golfs after 99 as they do not have a wastegate, they use the VNT 15 turbo.
A small discription of the system follows.
I believe the system functions like this.
Most wastegated Turbos operate off of vacuum, this system operates on pressure. The wastegate is normally open and diverting exhaust gasses all the time. To develop maximum boost the wastegate actuator diaphram is pressurized which shuts the diversion of exhaust gasses allowing them to drive the turbo. This would make it a failsafe system, if a component in the system develops a leak or obstruction the result is less total boost, and not excessive uncontrollable boost. The wastegate would fail to operate, and therefore the majority of exhaust gasses are diverted to the exhaust system, boost would be limited to around 9psi in this case at maximum load whereas normally it will peak at 15psi and settle to 13 continous.
The system is controlled by the ECU through a wastegate solonoid valve. Again to be failsafe the solonoid is set so that when it is off the pressure signal sent to the wastegate actuator is derived from the pre-turbo intake system of the engine. Very little pressure is applied and therefore boost is limited. When everything is working as it should, pressure supplied directly from the turbo is applied to the wastegate solonoid valve (hereafter refered to as the WSV) via the red hose, it attaches to the compressor side of the Turbo with a banjo fitting. The ECU sends a ground signal to the WSV to actuate it, this in turn allows the pressure from the red hose to flow to the blue hose. The blue hose is attached directly to the wastegate Actuator diaphram. This activates the actuator, closing the wastegate and allowing more boost pressure. When the ECU senses too much boost by means of the MAP sensor (located in the ECU, the signal is taken by hose off of the upper intercooler return line to the intake manifold)it removes the ground signal from the WSV and it vents the actuator diaphram to the intake via the black hose.
The WSV is located in the left firewall near the airbox. The problem as I percieve it is that the black hose is located near the PCV inlet of the intake. This area becomes very dirty if the PCV is connected on the engine. Some of this crud finds it's way into the WSV and maybe even the actuator itself. The valve becomes partially blocked which will not allow full pressure to the actuator. The sysmptoms of this will be, a code being tripped in the ECU where the specified boost the ECU is expecting to see is not what is actually availible, the actual boost pressure is to low, the code is listed as Manifold Absolute Pressure difference detected or intermittant. This will generally thow a CEL(check engine light) and power will be reduced until the ignition switch is cycled off and then on. This condition will normally occur under high boost demand, ie..going up hills, 5th gear and above 3000 rpms.
Failure of the WSV will cause this problem, as will leaks in the red or blue hoses, or the actuator diaphram at the turbo is ruptured, or there is a kink or obstruction in any of the hoses or obstruction in the valve.
The first order of business will be to bypass the PCV. Remove it from the intake port, plug the port and attach a PCV filter to the outlet port on the valve cover with a length of 3/4" hose. The comprehensive proceedure for this has been outlined by others.
Next, clean the intake elbow thouroughly especially in the area around the small black hose which exits off the intake elbow. remove this hose from the intake and the WSV and spray contact cleaner into the hose until it comes out clear, be sure to use a product that is not harmfull to rubber or platic, test it first on some ABS plastic, and on a small section of hose to make absolutely sure it's not going to eat your hoses up. Once you have cleaned the black hose, remove the Blue one and red one and do the same. The WSV is in a small rubber mount that pulls straight up to disconnect it from the mount. Remove it and clean it completely. I would recommend spraying the ports while actuating the valve, this would require rigging up a connection to 12vdc on the connector and cycling it while spraying cleaner into the ports. I would also recommend some compressed air that can be purchased from most electronic supply houses to blow out the lies and valve before reassembly. Make sure the banjo fitting at the turbo is clean, securely connected, none of the lines have kinks or holes, it may even be a better idea to replace the lines. A hand pump can be used to verify the diaphram actuator is functioning properly, 13 to 15 psi should open it completely. If it will not open, the diaphram is shot, this can be replaced as an assembly, it's bolted to the turbo on a bracket. Keep in mind that the wastegate itself could have crud preventing it from closing completely. To clean this would require the exhaust Downpipe be removed and it would have to be cleaned through the exhaust outlet of the turbo. I hope this helps. I would appreciate any corrections or suggestions anyone has.
[This message has been edited by valois (edited November 07, 2000).]