It was there yesterday morning........
Some of you may remember my posts in the past about losing boost pressure intermittently. Well it started to do it again recently, this time more regularly. If I turned the ignition off and back on again it would come back, so I'd always wondered if it was sensor related - either faulty or getting values it wasn't expecting and going into safe mode. When it had done it in the past it ended up having a new inlet manifold vacuum pressure sensor, which seemed to improve things a bit - but it still did it once or twice subsequently.
On the most recent occasions, when the boost went it was sometimes, not always, accompanied by an ELM (spanner) light - something that it had never done before, but turning the ignition off and on reset it all and got the boost back. Then one day a week or so ago it went again, but this time the boost never came back no matter what I did - removed the remap, disconnected the battery for a while etc. etc - it didn't come back!
I did a few diagnostics on the car - checking sensors, boost pressure solenoids etc. (thanks to Rickyroo BTW on the pointers there on how to check them) and all came up fine. The wastgate actuator looked like it was fine and wasn't loose or anything - so I was a bit stumped.
Bizarrely a few days later the boost came back. Equally bizarrely when I came to the car a couple of days later there was no boost there from the start, but within 30 seconds of setting off it suddenly kicked in! Then a day later it went within a minute of driving off and didn't show any signs of coming back.
After doing a bunch of Googling and looking on a whole lot of different forums (not Vx or Saab ones but a turbo is the same principle no matter what car it's on) I was convinced more and more that it was a wastegate problem, so I set about removing the actuator arm and diaphragm to see if the diaphragm was working okay and whether the waste gate arm was stuck or anything. Diaphragm tested out okay (just needed to attach a bike pump and put some air through it to see if the rod moved - it did), so I removed the arm so that the lever that controlled the wastegate inside the turbo was now free to move - except it didn't. It had limited movement and felt like something was stopping it from moving fully. Next step was to remove the exhaust downpipe from the turbo - a bit of a number as the bolts have limited access due to the BSR pipe being larger. Got it off, got a mirror to look into the exhaust side of the turbo and saw the problem!!
Couple of pics after the turbo was removed to explain....
The turbo. You can see the wastegate actuator (long rod down side of turbo) with the diaphragm attached to it at the top. One of the boost pressure hoses plugs into this diaphragm and as the boost increases the diaphragm moves, in turn moving the rod on the side and gradually opening the wastegate to release excess boost by means of the lever going into the turbo.
Here you can see the disc covering the wastegate that is opened and closed by the actuator depending on the pressure. The disc is normally held onto the arm by the little pin on the disc being attached to the arm. Here you can see there is nothing holding it! - it's come detached and headed off down the exhaust pipe.
This meant that the disc didn't lift up as the arm moved, leaving the disc just sliding around over the wastegate hole. The reason for the limited movement of the arm was due to the arm resting on the pin of the disc (which had moved).
I'm guessing that what had been happening was the disc was moving around and sometimes covering, or half covering the hole so causing boost to vary from what was expected, causing other sensors to pick up these differences and making the car then protect the turbo (safe mode) by releasing the pressure elsewhere - ambient air valve (recirculating dump valve) I'd expect.
A new turbo from Vx was £500+ - err, I don't think so - so I rang Turbo Technics in Northampton (the people when it comes to turbos IMO - especially Garret ones) and had a chat to see if the disc could be refitted/replaced. Yep, not a problem and it should cost around £60 - bargain!! If they thought the turbo needed a bearing/seal service (replacement) then that'd be £195 - and that would be the turbo rebalanced again on their extremely accurate machines. If they thought there was no need for the service then it would just be the wastegate repair. Given the mileage, 60,000, and the fact that I'll have the car most, if not all, of next year and add another 15-20,000 miles to it - if it was 50-50 as to whether they thought it'd benefit from the bearing and seals service, I'd get it done. Then I'd know the turbo would be okay for all the time I've got the car. I'm in no hurry to remove it all again in the future!!
So yesterday I got down to removing the turbo for them to collect on Monday. Fairly involved job, but I worked through it step by step and methodically - removing oil lines, coolant lines, sensors, boost pressure solenoids, exhaust downpipe, charge air pipe and other ancillary bits and pieces............
....all due to this little bit coming off!! lol
So, it'll be picked up tomorrow and with them Tuesday. They said it'd be with them for three days, so I'm hoping it will leave them Thursday and get to me Friday so I can fit it at the weekend and hopefully that'll be the end of any of my boost issues.
EDIT: Latest update here.
EDIT 2: Now all fitted back on again.