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Boost control valve testing

1381 Views 75 Replies 7 Participants Last post by  BobSaabit
I'm trying to troubleshoot low boost on my 2000 9-3 SE (b205r).

I've seen some contradictory information on troubleshooting. If I disconnect the electrical connector will the waste gate stay shut?

I'm Checking the bypass valve (B235R, B205L/R) – 9-3 2000 | SAAB Workshop Information System Online it talks about troubleshooting the Checking the bypass valve (B235R, B205L/R). Is this the vacuum operated part that actually connects to the waste gate via the pushrod?

I assume that if I disconnect the vacuum line from the part that actually connects to the waste gate via the pushrod that the waste gate that the waste gate will remain closed also.

Thanks,
Eric
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Discussion Starter · #22 ·
Reach down where the hose that comes from the intercooler and goes to the charge air pipe is and check it with your hand. Looking isn't good enough because when it blows off, it stays roughly in place but spews all your charge air under boost .

You don't need to plug the W line. It's blowing air out, not pulling it in. You can if you want to but it shouldn't matter in the context of testing the turbo hardware.

Wastegate is shut when engine is off. Or at least it should be. Reach down there and try to move the lever. It should be very hard to pull. When the engine starts, it should stay in the same position with the W hose disconnected.

If you want to actually see the wastegate to verify if it's closed or open, you would need to remove the downpipe. That's only three nuts on the turbo studs, but if they haven't been off in a long time they can be a real PITA - especially the bottom one on your T7. You need a short handled 13mm wrench and some time. It's usually about 1/8 turn at a time, flip the wrench, another 1/8 turn, etc. A small MAPP gas torch helps. Soaking with PB Blast or Kroil or similar over three days before helps.
When you write "the hose that comes from the intercooler and goes to the charge air pipe" I assume you mean on the discharge side of the intercooler? I tried tugging on the hoses that connect to intercooler on both the input and discharge sides and they both felt firmly attached to me.

I tried moving the waste gate lever. I couldn't move it toward the diaphragm box but could get it to move away from the diaphragm box with some difficulty. I believe pushing the waste gate lever toward the diaphragm box would be closing it and away would be opening it, so it seems okay at first glance.

I plan to check the waste gate and the endplay on the turbo after I change a power steering hose on our MDX.
 

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I tried moving the waste gate lever. I couldn't move it toward the diaphragm box but could get it to move away from the diaphragm box with some difficulty. I believe pushing the waste gate lever toward the diaphragm box would be closing it and away would be opening it, so it seems okay at first glance.
That is backwards.... the wastegate arm should move towards the actuator (opening the wastegate) not away from the actuator (closing the wastegate). It's really difficult - borderline impossible - to move by hand. I would maybe see if you could borrow a pressure pump (like a Mityvac) from an auto parts store if you wanna accurately test this.
 

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Discussion Starter · #26 ·
That is backwards.... the wastegate arm should move towards the actuator (opening the wastegate) not away from the actuator (closing the wastegate). It's really difficult - borderline impossible - to move by hand. I would maybe see if you could borrow a pressure pump (like a Mityvac) from an auto parts store if you wanna accurately test this.
Assuming that it's vacuum operated and not pressure operated it would make sense for the arm to move towards the actuator, since it would be sucking the internal diaphragm that way.

I have a mity vac that I mostly use for bleeding brakes. I'll hook it up and see what happens.

I guess I can do the vacuum test on the Bypass valve too while I'm at it.
 

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Discussion Starter · #27 · (Edited)
Assuming that it's vacuum operated and not pressure operated it would make sense for the arm to move towards the actuator, since it would be sucking the internal diaphragm that way.

I have a mity vac that I mostly use for bleeding brakes. I'll hook it up and see what happens.

I guess I can do the vacuum test on the Bypass valve too while I'm at it.
I hooked up my mighty vac to the actuator and it didn't move when I pulled a vacuum. I could move the the wastegate operating lever away from the actuator but not towards the actuator. I believe that the actuator's vacuum would pull the wastegate operating lever away from the wastegate and that a spring inside the actuator would push it shut it seems like maybe the actuator or the waste gate itself are stuck in the open position somehow. It looks like wastegate actuators are no longer available and I don't see a part number for replacement doors?

If I pulled the wastegate actuator off the car I should be able to push the pushrod into the unit slightly and a spring would push it back, right?

My mighty vac doesn't have a gauge on it but when I hooked up it to the wastegate actuator and to the diverter valve it made a sucking sound when I disconnected it after a few seconds so I could tell that it was pulling vacuum on the two components.
 

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Discussion Starter · #31 ·
If there's pressure inside the wastegate actuator then I should think it would have to push open the wastegate, not pull the door open. Talking about the part that actually opens and closes the wastegate, not the solenoid.
 

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Just to triple verify... definitely pressure coming at the wastegate through the W hose. It starts closed, boost building blows it open subject to whatever limits the airflow to it like the (Saab Term) Solenoid Valve.

The Bypass valve is vacuum operated. When you go off throttle, vacuum appears and it pulls the (Saab Term) Bypass valve open. On the T7, that's subject to the operation of the (Saab Term) Turbo Bypass Control Valve on the firewall.
 

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I'm trying to troubleshoot low boost on my 2000 9-3 SE (b205r).

I've seen some contradictory information on troubleshooting. If I disconnect the electrical connector will the waste gate stay shut?

I'm Checking the bypass valve (B235R, B205L/R) – 9-3 2000 | SAAB Workshop Information System Online it talks about troubleshooting the Checking the bypass valve (B235R, B205L/R). Is this the vacuum operated part that actually connects to the waste gate via the pushrod?

I assume that if I disconnect the vacuum line from the part that actually connects to the waste gate via the pushrod that the waste gate that the waste gate will remain closed also.

Thanks,
Eric
Have you checked inside? I found the waste-gate flapper rotted right off the
stem on my '99 9-3
 

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2008 9-5 2.3T 2011 9-3 Turbo4
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The waste gate was integral to the Garret turbo on mine, a linear.
Had to replace turbo. My Saab tech had to drop the down-pipe for some reason
I can't remember and he noticed it. Good luck man! I love the 5 doors!
 

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I'm talking about the actual wastegate. Wondering if it's bad if I can replace it.
It would be very unusual for it to be bad. Possible, unlikely.

Pull the downpipe off at the turbo. Check it. I'm guessing it's OK. While you're in there you can check shaft play (axial and radial) and get a good look at the wheel. Look at the housing too for evidence of damage (impeller scraping).
 

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Are you talking about the actual wastegate or the actuator? The wastegate is part of the exhaust housing on the turbo... the actuator is a separately replaceable part.
The actual waste-gate inside the turbo housing. I think that problem
came up a couple of times. I have a faint memory of the disc
on the flapper coming loose on another '99 9-3
 
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