Turbo boost solenoids: where they are, how to test and replace them

What owners saw

• Chatter on lift-off. One owner (2009) had a flutter or chatter on lift-off between gear changes under load. His replacement solenoid, about £20 from Vauxhall, cured it. Another owner had the same on part throttle, which he found very annoying on track at Rockingham, and a new solenoid "removed all the awful chattering and fluttering". He said the symptom had been there since he bought the car in January, and a new AET turbo hadn't cured it. A third owner (2010) asked for the part because of chatter on lift-off.
• A lull at 3,000 rpm. In 2014 one owner reported the problem fixed after spending £32.32 in a thread about the solenoid, and another owner asked "lull at 3k sorted?". The post doesn't say outright what he bought, but the context points to the solenoid.
• Low boost. One owner (2013) changed both solenoids to see whether they were behind his boost problems. Afterwards he thought his stage 2 had probably hit a genuine 1 bar for the first time, with a sharp overboost to around 14 to 15 psi that then settled at 10 to 12 psi. He asked whether that is normal and nobody answered directly.
• Not always the solenoid. One owner said his boost problem ended up being a leaky vacuum box. Another owner (2013) found a lower intercooler pipe half popped off. A third owner said to check all the pipework from the recirc valve back to the inlet solenoid, because pipes can pop off the solenoid.
• Didn't cure it. One owner (2017) had a flutter that he couldn't cure even after trying an electronic boost controller and bypassing the inlet solenoid. Another owner said that changing both solenoids was one of several things that over time improved his surges significantly. See the boost diagnosis guide.

The two solenoids

• On the turbo. One owner described it as on the right-hand side of the heat shield, where the intake pipe goes into the turbo: take the intake pipe off and you will see a small solenoid with three pipes and an electrical connector. Another owner said this is the solenoid that controls the wastegate actuator, and that in his experience it is not normally the problem.
• By the inlet manifold. One owner said the other one, on the opposite side of the engine from the turbo, controls the recirc valve and therefore the amount of boost, and that reaching down by the throttle body you can see where two vacuum pipes split off from it. Another owner called this the inlet one: the one by the inlet manifold, closest to you looking from the back, which connects directly to the recirc valve.
• Which is which for a turbo swap. One owner said a turbo swap changes only the wastegate actuator and its solenoid, because the other solenoid is by the inlet manifold. That fits another owner's flutter surviving a new turbo.
• Both from above. One owner told another owner you can get to both from above, so you don't need the undertray. Graeme had assumed otherwise. A third owner cursed the position of the vacuum solenoid and called it a pain.

Testing one

One owner's test (2009), from his own case: he said it was what he found to be his problem and should be used for information only.

1. Remove the solenoid.
2. Blow into the metal inlet piece. Air should come out of the tee piece outlet next to the electrical connector.
3. Put a finger over that outlet and blow into the inlet again. The valve should now seal and you shouldn't be able to blow.
4. If air escapes through the unblanked outlet, the solenoid is unserviceable.

One owner's version (2017) is similar, with a power check: blow in the flow direction and air should come out of only one of the exit tubes. Put your finger over that one and blow hard: no air should leak from the other. If that works, connect a 12 V feed to the solenoid and it should divert the air out of the opposite tube to last time. He also said to make sure the original isn't leaking "like before", which isn't explained in the thread.

Part numbers and prices

• In 2009 one owner said the part is about £20 from Vauxhall. In 2010 AutoVaux quoted another owner "valve, solenoid, turbocharger wastegate actuator vacuum control" at £20.45 plus VAT, with postage from £2.63. Nobody confirmed it was the right part, and another owner asked for confirmation.
• In 2013 one owner bought a pair from AutoVaux. The solenoid he took off the turbo was marked 7.28201.00, 12V 02T289, GM 90 424 141. The pair were marked 7.01039.02, 12V 12T300, GM 55 577 092 and 7.01024.00, 12V 12T284, 5900 117 0402, GM 55557806. Neither matched the old one, and he decided 806 was the turbo side and 092 the inlet side. Another owner said that was correct and posted a photo of the turbo one. We don't know whether the old number had been superseded. Check against your own old part.
• In 2011 one owner gave a different number for the inlet solenoid: "rear" (inlet or vacuum, on the boot side of the engine bay) 55557829 and "front" (boost, on the bulkhead side above the turbo) 55557806. The front one matches the turbo-side number above, but his rear number doesn't match another owner's 55 577 092. We don't know which is right or whether one superseded the other. One owner also put them at about £20 each.
• One owner said he had a large Word document explaining the whole boost and wastegate system with pictures, locations and part numbers, which he emailed on request. It isn't in the threads.

Removing and fitting (2009 to 2013)

• Turbo side. One owner said you don't need to remove the heat shield, just the inlet pipe, and to put something over the turbo outlet while the pipe is off. Another owner took the heat shield "chimney" off and said the job took about an hour. It was fiddly and easier with the engine lid off, and a good chance to check all the pipework. A third owner said the bolts on the turbo one were simple star drive.
• Several owners (2011). One owner said the turbo-side solenoid is on a bracket held by 3 Allen head screws, which also attach the recirc valve to the right-hand side of the turbo. He said the inlet manifold solenoid is an easy job, while the turbo-side one and the recirc valve need the intake pipe off, and the vacuum hose clips are a pain. Another owner said he replaced the turbo-side solenoid in about 20 minutes. It is held by Torx bolts, and needle-nose pliers and patience work on the small clips, which he undid before unbolting the solenoid. You only need to take one bolt out and slacken the other.
• Fixings. One owner said there are two Torx bolts (E8 or E10, he thought): slacken the lower one, and remove the top one completely after taking off the three hoses and the electrical connector. Another owner couldn't remove the bolts on the inlet side, which looked like male star drive, and fell back on a tie wrap to hold it in place. A third owner said the recirc solenoid and vacuum box bolts are Torx, that many engine bolts are, and that you need a female Torx socket set.
• Hose clips. One owner found the clips on the vacuum hoses very awkward and asked about tie wraps. Another owner said that when he refitted his recirc he didn't bother with the bracket for the actuator solenoid, used a tie wrap, and the hoses stayed on without the clips. That was his own choice, not a recommendation.
• Connectors. One owner said the plugs are a pain to unplug, but another owner found them really easy.
• Moving it. One owner asked whether anyone had relocated the turbo solenoid to the bulkhead. Another owner had, and wasn't sure it was a good idea: a longer vacuum pipe means longer delays in the pressure signals. He didn't think the OEM one would get hot, because it sits on the compressor (cold) side.
• Bypassing. One owner said he has "bypassed mine altogether", without saying how or what the car did afterwards. Don't copy that without knowing the effect on boost control.