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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 23620
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I've just changed the turbo cartridge core as the bearings

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I've just changed the turbo cartridge core as the bearings had gone on my old one. I'm now experiencing a lack of power. I have tried altering the waste gate with very little change. When engine is cold it's fine but as soon as it warms up it goes into limb mode and I have no power. Does this mean the waste gate actuator has gone as well?
Assistant: Is the power loss consistent, or does it fluctuate?
Customer: It takes forever to build up speed through the gears. It feels fine in first worse in third. It's more sluggish between 1500-2000revs
Assistant: What year is your Turbo?
Customer: Been on the car since I bought it in 2012. Car is 2010/2011. The new cartridge I bought last week.
Assistant: Are you fixing your Turbo yourself? What have you tried so far?
Customer: I didn't have any power issues before just a noise checked turbo and I had play in the shaft. I've got no noise but now no power
Assistant: Anything else you want the mechanic to know before I connect you?
Customer: Can't think of anything. Just wanted to know if there is a specific way of setting up the wastegate or if it needs replacing too.
Customer: replied 6 months ago.
I have a vauxhall insignia 2010 Sri.


I'd first check all the high pressure hoses post turbo/s for any split hoses or cracked metal pipes, also check the ends of the intercooler as its not unheard of to pop the end caps off under high boost.

If this is OK then check the small vacuum lines to the turbo and its connected control solenoid on the bulkhead, any cracks or leaks can give turbo issues

Also check that the vacuum hose running to the dump /or turbo bypass valve is intact with no leaks as if the dump valve is opening prematurely you'll be losing all your boost

The dump valve is on the turbo boost air (post compressor) side its there to blow off or 'dump' the excess boost pressure you get when you close the throttle ( like just before a gear change)

the important thing with a dump valve is that it seals properly when its not being operated if the valve has a torn seal or a broken spring then it'll blow off before it should and you'll lose boost pressure

this video shows how you can test it

one other possibility is that the wastegate actuator spring has gone soft so allowing the wastegate to open prematurely - if your actuator has a threaded end you can increase the preload on it to see if this improves things otherwise these units are quite cheap compared to a new turbo so it may be worth trying a replacement.

as for the wastegate then this is on the exhaust side and 1st thing to check is if the wastegate 'penny' or flap can be fully seated
if you remove the wastegate actuator and then look inside the turbo exit you'll see the wastegate penny moving back and forth as you move its arm if you smear a little grease or engineers blue onto the face of the penny and snap it shut and reopen it you shoudl hopefully see the seal line all around the penny

if thats OK you can then test the wastegate actuator with compressed air to check its opening up this shows if its going to be able to control boost
this video shows how ( from about 2 mins in)

and to check the spring ( is it blowing off too early) you need a spring balance or some other method of measuring the spring force as shown in the previous video

do you still need help?
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Thanks Matt

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Customer: replied 5 months ago.
I have checked all the hoses no leaks, the spring feels fine in the actuator. It doesn't have a wastegate as it is a vnt turbo. From what I can hear it does not seem to be going out the dump valve. I haven't had a chance to fully take the front off the car apart as I need the car daily. Just a quick one on the boost control valve. When you put the revs up should the needle drop off on the pressure gauge. It currently sits at 23inHg and holds but when I accelerate the pressure doesn't change.


if the boost pressure stays at 23in Hg ( 0.8bar) then this is fine as the turbo should hold onto the boost level through the rev range

so if there's plenty of boost but no power then I'd next check that the throttle is opening fully and the fuel pressure is also OK

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

You can also get this issue with contaminated fuel , if there’s water or dirt in the tank then either the petrol floats on top of the water or the filter sock on the pump is choked up – so if the other things check out then I’d consider pulling out the fuel pump and cleaning the filter sock

And one other thing to try is to loosen off the fuel filler cap, as there’s a 1 way valve built into the cap to let air into the tank and so prevent a vacuum from being created as the fuel leaves the tank to the engine
If this helps then replace the cap with a new item