imoyes
05-08-04, 01:48 PM
This is intended as another idiots guide, seeing as how it's written by an idiot. :cheeky:
The Positive Crankcase Ventilation (PCV) system is intended to create a negative pressure in the rocker cover of your engine. This is intended to help the piston rings to seal and therefore help the engine to maintain higher compression. Good thing.
How this is acheived is by connecting a hose to the top of each rocker cover. This is fed, via a pipe, to the throttle body and the accordion hose. The idea is that, under low throttle/revs the throttle body will provide a vacuum source, whilst under open throttle/high revs, the turbo will provide a vacuum source via the accordion hose.
OK now you need to think about this for a moment. :bigeyes: Since the throttle body and the accordion hose are providing a vacuum source they are sucking oil-vapour-laden air out of the top of your engine and pumping it into your air intake. Bad thing.
Now, as you can see above, there is a is a trade off. If you remove the PCV from the accordion hose and the throttle body and don't replace them with another vacuum source then you will have solved the bad thing but you won't have the advantage of the good thing. Racing engines use a small, electrically powered, vacuum pump as the vacuum source.
This thread assumes that YOU HAVE DECIDED that you are prepared to forego the positive effects of PCV in favour of a yuck free air intake system.
I'm going to concentrate, mainly, on removing the existing system and let you decide what to replace it with, although I might suggest a few ideas.
Start by removing the top intercooler pipe, the one that goes from the front inside drivers wing to the 3000 pipe on top of the engine.
Remove your air box.
Remove the accordion pipe. Careful, it has a little hose underneath that always catches me out. You'll have to detach all of the hoses that attach to the accordion hose to get it out.
The PCV pipe is the one bolted to the back of the 3000 pipe, with the two short hoses that go to the top of the engine. It's held on with two bolts, the one you can see, to the 3000 pipe and another, over the turbo, to the engine block. It's a bugger to get to. I decided to get everything out of the way so.
Carefully, unplug the wiring from the Exhaust Oxygen Sensor (at least, I think it's the O2 sensor), that sticks up out of the turbo heat shield, at the other end of the wire, near the front of the engine block, by the power steering reservoir, and, just as carefully, detach the wire from the clips on the PCV pipe.
Remove the turbo heat shield and the turbo mounting bracket.
Now, de-skin your knuckles whilst removing the other PCV bolt. :)
The PCV pipe should now lift off the hoses on the rocker covers and throttle body and come away with the hose to attach it to the accordion hose still connected.
Now you have to plug up the holes in the accordion hose and the throttle body.
Turn your attention to the accordion hose. If you use some gentle pursuasion and a pair of big Mole grips you can coax the metal insert, that the PCV hose attached to, out of the accordion hose. Make sure you take the right one out, the others are for your Idle Speed Control and your Blow Off Valve. I used the filler plug from a MKIII T Limited Slip Differential to plug the hole, it's a perfect fit. I washed the hole out with washing up liquid and water and allowed it to dry, then I used some emery paper to abrade the inside of the hole a little. I coated the diff. plug with bathroom silicone sealer, slipped it into the hole in the accordion hose and clipped in place with the hose clip that had held the PCV hose in place.
Now it's the throttle body's turn. Remove one of the rubber hoses that held the PCV to the rocker covers. wash out the inside with soapy liquid and allow it to dry. Abrade the inside, a little, with emery paper. You can buy bolts with a 12mm diameter thread from B&Q. Cut the threaded end so that you have about 10-15mm of thread. Coat the thread with silicone bathroom sealer and slip it into the hose. Hold it in place with one of the clips that held the PCV hoses onto the rocker cover.
OK, now you can start to put things back together again, then we'll figure out what to do about your rocker covers, which currently have 12mm gaping holes in the top. :)
The turbo mounting bracket goes on first, it looks like it should go on after the heat shield but trust me. Bolt it on at the engine block but don't tighten it up yet.
The turbo heat shield is a night mare to line up. Don't forget to feed the wire for the sensor through before you start. I found that, if you start with the long 12mm bolt that goes through the mounting bracket first you'll save your sanity. Use a match, dropped into the bolt hole in the turbo housing to help you line up this hole with the hole in the heat shield and screw the bolt in about 1 turn or so. Jiggle the heat shield around until you can get the bolt at the rear to go through the heat shield. You'll find that if you keep the shield up on the first bolt, you just inserted, it goes over the second one easier. Last is the 17mm and he's relatively easy. Tighten them all down. Don't forget to go back and tighten the bolt on the turbo mounting bracket ot the engine block.
Don't foget to plug the exhaust sensor back in. You'll find that the wire wants to dangle close to the turbo housing. I felt uncomfortable with this. Under the pipe that bolts to the front of the 3000 pipe are two more thin pipes, welded to the big one. One of these carries the vacuum source to the Blow Off Valve Accuator. The other one isn't connected on most of our cars. It's used in America to attach a vacuum source, the throttle body again, to a valve used to vent evaporated fuel from the fuel tank to the inlet manifold. I cable tied the sensor wire to the end of this pipe, it's in just the right place to keep it up out of harms way.
Now reattach your accordion pipe, don't forget the little hose underneath and reattach your air box. Don't forget to tighten every thing up.
Now, what to do with those holes in the top of your engine?
I've seen a MKIII with two little K&N type breathers on the rocker covers, that looked cool.
One of our members (5;4;3;2;1) bought a PCV pipe from an NA (much simpler system) attached some rubber hose to it and lets it dangle under the car.
I bought a Jaz Can, breather/catch can from these guys http://www.motorstate.com and a PCV from an NA and attached the output from the PCV to the can with Silicone Vacuum Hose. The can has a neat little petcock on the bottom so you can drain it, so I attached a length of SVH to that too, so that you can drain it into an oil tray. The problem with this is finding somewhere to site the can, PITA!
Wow! I've just seen how long this is! Sorry!
The Positive Crankcase Ventilation (PCV) system is intended to create a negative pressure in the rocker cover of your engine. This is intended to help the piston rings to seal and therefore help the engine to maintain higher compression. Good thing.
How this is acheived is by connecting a hose to the top of each rocker cover. This is fed, via a pipe, to the throttle body and the accordion hose. The idea is that, under low throttle/revs the throttle body will provide a vacuum source, whilst under open throttle/high revs, the turbo will provide a vacuum source via the accordion hose.
OK now you need to think about this for a moment. :bigeyes: Since the throttle body and the accordion hose are providing a vacuum source they are sucking oil-vapour-laden air out of the top of your engine and pumping it into your air intake. Bad thing.
Now, as you can see above, there is a is a trade off. If you remove the PCV from the accordion hose and the throttle body and don't replace them with another vacuum source then you will have solved the bad thing but you won't have the advantage of the good thing. Racing engines use a small, electrically powered, vacuum pump as the vacuum source.
This thread assumes that YOU HAVE DECIDED that you are prepared to forego the positive effects of PCV in favour of a yuck free air intake system.
I'm going to concentrate, mainly, on removing the existing system and let you decide what to replace it with, although I might suggest a few ideas.
Start by removing the top intercooler pipe, the one that goes from the front inside drivers wing to the 3000 pipe on top of the engine.
Remove your air box.
Remove the accordion pipe. Careful, it has a little hose underneath that always catches me out. You'll have to detach all of the hoses that attach to the accordion hose to get it out.
The PCV pipe is the one bolted to the back of the 3000 pipe, with the two short hoses that go to the top of the engine. It's held on with two bolts, the one you can see, to the 3000 pipe and another, over the turbo, to the engine block. It's a bugger to get to. I decided to get everything out of the way so.
Carefully, unplug the wiring from the Exhaust Oxygen Sensor (at least, I think it's the O2 sensor), that sticks up out of the turbo heat shield, at the other end of the wire, near the front of the engine block, by the power steering reservoir, and, just as carefully, detach the wire from the clips on the PCV pipe.
Remove the turbo heat shield and the turbo mounting bracket.
Now, de-skin your knuckles whilst removing the other PCV bolt. :)
The PCV pipe should now lift off the hoses on the rocker covers and throttle body and come away with the hose to attach it to the accordion hose still connected.
Now you have to plug up the holes in the accordion hose and the throttle body.
Turn your attention to the accordion hose. If you use some gentle pursuasion and a pair of big Mole grips you can coax the metal insert, that the PCV hose attached to, out of the accordion hose. Make sure you take the right one out, the others are for your Idle Speed Control and your Blow Off Valve. I used the filler plug from a MKIII T Limited Slip Differential to plug the hole, it's a perfect fit. I washed the hole out with washing up liquid and water and allowed it to dry, then I used some emery paper to abrade the inside of the hole a little. I coated the diff. plug with bathroom silicone sealer, slipped it into the hole in the accordion hose and clipped in place with the hose clip that had held the PCV hose in place.
Now it's the throttle body's turn. Remove one of the rubber hoses that held the PCV to the rocker covers. wash out the inside with soapy liquid and allow it to dry. Abrade the inside, a little, with emery paper. You can buy bolts with a 12mm diameter thread from B&Q. Cut the threaded end so that you have about 10-15mm of thread. Coat the thread with silicone bathroom sealer and slip it into the hose. Hold it in place with one of the clips that held the PCV hoses onto the rocker cover.
OK, now you can start to put things back together again, then we'll figure out what to do about your rocker covers, which currently have 12mm gaping holes in the top. :)
The turbo mounting bracket goes on first, it looks like it should go on after the heat shield but trust me. Bolt it on at the engine block but don't tighten it up yet.
The turbo heat shield is a night mare to line up. Don't forget to feed the wire for the sensor through before you start. I found that, if you start with the long 12mm bolt that goes through the mounting bracket first you'll save your sanity. Use a match, dropped into the bolt hole in the turbo housing to help you line up this hole with the hole in the heat shield and screw the bolt in about 1 turn or so. Jiggle the heat shield around until you can get the bolt at the rear to go through the heat shield. You'll find that if you keep the shield up on the first bolt, you just inserted, it goes over the second one easier. Last is the 17mm and he's relatively easy. Tighten them all down. Don't forget to go back and tighten the bolt on the turbo mounting bracket ot the engine block.
Don't foget to plug the exhaust sensor back in. You'll find that the wire wants to dangle close to the turbo housing. I felt uncomfortable with this. Under the pipe that bolts to the front of the 3000 pipe are two more thin pipes, welded to the big one. One of these carries the vacuum source to the Blow Off Valve Accuator. The other one isn't connected on most of our cars. It's used in America to attach a vacuum source, the throttle body again, to a valve used to vent evaporated fuel from the fuel tank to the inlet manifold. I cable tied the sensor wire to the end of this pipe, it's in just the right place to keep it up out of harms way.
Now reattach your accordion pipe, don't forget the little hose underneath and reattach your air box. Don't forget to tighten every thing up.
Now, what to do with those holes in the top of your engine?
I've seen a MKIII with two little K&N type breathers on the rocker covers, that looked cool.
One of our members (5;4;3;2;1) bought a PCV pipe from an NA (much simpler system) attached some rubber hose to it and lets it dangle under the car.
I bought a Jaz Can, breather/catch can from these guys http://www.motorstate.com and a PCV from an NA and attached the output from the PCV to the can with Silicone Vacuum Hose. The can has a neat little petcock on the bottom so you can drain it, so I attached a length of SVH to that too, so that you can drain it into an oil tray. The problem with this is finding somewhere to site the can, PITA!
Wow! I've just seen how long this is! Sorry!