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Discussion Starter · #1 ·
My actuator has failed, i've tested it and once vacuum just drops off. Where is the best place to get a replacement, i've looked on ebay but i can't seem to see anyone selling the 150bhp ones. I'm also stuggling in finding part numbers, there are a couple of numbers on stickers (270706 121 and 552086180)
 

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Not sure you can replace the actuator... The stroke of the actuator is calibrated to give the correct level of boost at a given stroke distance.

Anyone else got experience of this?
 

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Usually the actuator is part of turbo and as said it is calibrated to the cartridge. However if you can get a used one that works you can set up yourself with a bit of patience..

Actuator should start to move 3-5 hg vac and reach max travel at 17-19hg vac.
 

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Discussion Starter · #4 ·
Maybe its something else that i'm not seeing. I've checked the vacuum on the actuator and the value drops off pretty quick as though the diaphram has perished, theres no air leaks either by looking, feeling and spraying.
Turbo boost is hardly there, you could be cruising along with revs just before turbo kicks in and the engine hesitates and then i change gear and sounds like an external wastegate chuffing is the noise(which i don't have).
On the vacuum lines is there a one way non return valve????
 

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If the actuator does not hold vac and drops off then that’s your problem,assuming you have used your vac tool directly on the actuator so as to eliminate any pipework.
 

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Scrap yard (cheap and as new sometimes).

If not you should buy turbo solenoid in Garret distributor parts because Alfa sell full turbo only. Be carefully with fake solenoids (bad calibration).

I didn't find anything with your references.
 

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Discussion Starter · #8 ·
I put the tool directly on the turbo actuator and the vacuum dropped off, I tried putting the tool on the vacuum pipes but nothing happened ie I couldn’t get vacuum ( is this normal or is there a one way valve in the system)?.
I wouldn’t want to scrap it, it’s only done 50,000 miles, so not a scrapper.
I’m looking at other ways like capping off and pressure testing the inter cooler side, but the actuator looks a good culprit at the moment
 

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The actuator is going to be the problem if it does not hold vac, basically when in operation vac is applied to the actuator via the N75 valve to give full boost. As boost pressure is reached the vac drops off. If your unit does not hold vac then it will not reach full boost position and also boost will not be controllable.

I would replace the actuator before doing anything else.

As for testing pipes easiest way is connect output from pump and run engine to see what vac it is producing,you should get pretty much the same vac out of N75 to turbo actuator when at idle.

There are replacement actuators on fleabay when searching for Vauxhall 1.9cdti ones.
 

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Discussion Starter · #10 ·
I’ve tested the actuator and it’s holding vacuum without dropping. I’ve pressurised the boost hosing in and out of the intercooler with no leaks. The car still doesn’t boost as it should, I have an old Volvo with 160,000 miles and that is supposed to be 140bhp and that boosts up better than my Alfa that’s only done 50,000 150bhp. I have a serious problem, just work out wear.
 

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This sounds simply like a lack of vacuum with maybe an unorthodox testing procedure. Its very simple, at idle there should be constant vacuum at the hose tip, So follow the hose back to unit on front panel, from there to vac module and so on, checking with your finger for suction at the end of the hose until you find which of the modules in the chain is not doing its job. Either that or find someone to do it for you.
 

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Discussion Starter · #13 ·
Hi sorry the pipe I was using was slightly too big, I was doing it from the top because I thought it was going to be a quick fix.
I sorted the pipe and the actuator is fine, I also made my own boost pipe tester, and there are no leaks.
I can feel vacuum from the hose, I just need to test it with the tool, anyone know how much vacuum should be reading at idle?
 

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Discussion Starter · #15 ·
Hi right I’m getting just under 20 on the vacuum, is there a switch on the gearbox - I thought I read some where but can’t be sure. I’ve also cleaned the MAP sensor which had some carbo deposits on it, anything else I can try?
 

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Hi right I’m getting just under 20 on the vacuum, is there a switch on the gearbox - I thought I read some where but can’t be sure. I’ve also cleaned the MAP sensor which had some carbo deposits on it, anything else I can try?
Any fault codes on the ECU to give us something to go on?

I see a lot of dodgy N75 valves (the electronic solenoid which provides vacuum to the actuator), but that is a guess until you have diagnosed it correctly.
 

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Discussion Starter · #17 ·
Hi no codes in connection with turbo, there was preheat something (I’ll check) and unknown 040110 maybe 040100 (I’ll check).
I thought it might be down to the bottom boost hose because it felt soft, but that’s on the pressure side and has been pressure tested for any leaks.
 

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Discussion Starter · #18 ·
Just remembered when driving say 2nd gear I’d get to between 2-2500 revs and it would chuff and the power would hesitate on and off like a limiter until I changed gear, strange feeling.
 

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The vacuum actuator on the turbo is rated 20ins.Hg max according to a reference I found on the web, 3 years ago. I measured maximum deflection of the actuator at ~17ins Hg. If you have 17ins.Hg, any boost issues are likely due to leaks in top or bottom boost hoses, blocked air filter element due to not having been changed in 10 years because it's awkward, or sticking turbo VGT vanes. All are common. Less common, a leaking intercooler.
 
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