cracked manifold replaced - need more pointers on what to check next re low boost

[wpoll]

Originally Posted by omodos

Cheers for reply...dunno if any garage out here will fathom this request, in meantime i disconnected the 2 hoses off the vacum.accumulator 'tank' so thus bypassing it, and connected these 2 together hoses together...will do school run then to work and assess if any change

Bypassing the vacuum reservoir could make things worse, not better. It's there for a reason.

At Clavurion has mentioned - you need to check that the VGT vanes are being operated - your issue has all the hall-marks of the VGT actuator not operating correctly. There are many possible causes for this and the very first and most basic diagnostic step is to ensure that the actuator is moving the turbo vanes at start-up. Further diagnosis beyond this gets more complicated but let's get this first step out of the way and then proceed from there.

Here's a video of the M47 (4-cylinder version of the 6-cylinder M57) VGT actuator in action: -

https://www.youtube.com/watch?v=W3zOrUHxhFg

[omodos]

Originally Posted by wpoll

Bypassing the vacuum reservoir could make things worse, not better. It's there for a reason.

At Clavurion has mentioned - you need to check that the VGT vanes are being operated - your issue has all the hall-marks of the VGT actuator not operating correctly. There are many possible causes for this and the very first and most basic diagnostic step is to ensure that the actuator is moving the turbo vanes at start-up. Further diagnosis beyond this gets more complicated but let's get this first step out of the way and then proceed from there.

Here's a video of the M47 (4-cylinder version of the 6-cylinder M57) VGT actuator in action: -

https://www.youtube.com/watch?v=W3zOrUHxhFg

oops just drove a few km with the vacuum reservoir bypassed ...righto ok at first chance will take a look and see, just considering also buying the vacum converter and telling mechanic to stick it in anyways but I guess one step at a time eh https://www.realoem.com/bmw/enUS/sho...36#11747796634

PS anyone I speak to (colleagues etc) the minute I explain issue they say its the turbo....well yes it aint spooling up before 2000rpm, but as I have read in the posts it could be quite a few reasons.....no necessarly and issue with turbo kicking my slef for no insisting mechanic delved into further and even preemptively change out the pressure converter whilst he was down there....

[wpoll]

Originally Posted by omodos

oops just drove a few km with the vacuum reservoir bypassed ...righto ok at first chance will take a look and see, just considering also buying the vacum converter and telling mechanic to stick it in anyways but I guess one step at a time eh https://www.realoem.com/bmw/enUS/sho...36#11747796634

Won't do any damage but won't help either...

You linked it to the incorrect pressure converter - you have indicated the EGR pressure converter. The turbo control pressure converter is here: -

https://www.realoem.com/bmw/enUS/sho...diagId=11_2978

Same part and part number though.

I wouldn't replace this on spec unless diagnosis shows it to be faulty (which it may be...).

[omodos]

Originally Posted by wpoll

Won't do any damage but won't help either...

You linked it to the incorrect pressure converter - you have indicated the EGR pressure converter. The turbo control pressure converter is here: -

https://www.realoem.com/bmw/enUS/sho...diagId=11_2978

Same part and part number though.

I wouldn't replace this on spec unless diagnosis shows it to be faulty (which it may be...).

jeez yes same part numbers eh well spotted...and different item you think no likely i think?, do you reckon the item in link you sent has an atmospheric filter on it that can get gunked up causing issues especially if you saw the sooty state of the area of the engine nearest to cracked manifold....?it was not in a good state... anyway the test I did was to bypass the 'barrel' and use a rigid straw as in pic in yellow to link 2 tubes ...i took it off now, back to 'normal'

[wpoll]

Yeah, there is a small filter on the pressure converter and I guess it could be blocked by the exhaust soot - not 100% sure how this would affect it's operation but I guess it could well be compromised by a dirty filter - internet "evidence" suggests this is the case.

Slightly different pressure converter model but you can see the filter, second item from left.



(Image from this thread - which is interesting... https://www.e90post.com/forums/showthread.php?t=1589166

The vacuum reserviour is simply to provide a near-constant vacuum "pressure" (negative pressure) for the pressure converter to work with, since it opens and closes very rapidly to modulate the VGT actuator position. Without this reservoir, the pressure converter is working with a vaiable vacuum level, meaning the VGT operation is dependant on vacuum level (via RPM).

[omodos]

okay matey yes, right so not noticing any improvement when the accumulator reservoir is bypassed means what? the accumulator could still be duff? whipping it off blocking one end and blowing through on the other end when submersed in water to see if it has bubbles coming out of it to see if it is leaking is a good test

[wpoll]

Originally Posted by omodos

... so not noticing any improvement when the accumulator reservoir is bypassed means what? the accumulator could still be duff? ...

It probably means nothing... if the boost is already compromised then removing the reserviour probably won't make it much worse. Especially if your fault IS the pressure converter, which is "down-stream" from the vacuum reserviour and will mask the reduction in vacuum stability.

First, check the VGT actuator operates as it's supposed to. Then you could check the vacuum reserviour (and the closed pressure converter) with a vacuum gauge, like in my write-up. If those tests come up good, you might want to then remove and test the pressure converter. Or, as you suggest, simply replace it, since in your case the labour costs will likely exceed the cost of the part.

[omodos]

Originally Posted by wpoll

It probably means nothing... if the boost is already compromised then removing the reserviour probably won't make it much worse. Especially if your fault IS the pressure converter, which is "down-stream" from the vacuum reserviour and will mask the reduction in vacuum stability.

First, check the VGT actuator operates as it's supposed to. Then you could check the vacuum reserviour (and the closed pressure converter) with a vacuum gauge, like in my write-up. If those tests come up good, you might want to then remove and test the pressure converter. Or, as you suggest, simply replace it, since in your case the labour costs will likely exceed the cost of the part.

Yup thanks fella for feedback, i guess good chance may need 2 of those pressure covnerters one for the EGR and one for the turboboost control.... out of curiosity when do you feel that boost on your X5 from the turbo? I am adamant after 14 odd years of driving mine for sure kicked in in the 1500-2000 range....

[wpoll]

Not sure I can feel boost at 1,500rpm but I can certainly hear the turbo spooling up by then. Which doesnt mean it's creating significant boost at that low rpm - but perhaps my pressure converter is getting pretty tired too!! ;-)

[omodos]

Originally Posted by wpoll

Not sure I can feel boost at 1,500rpm but I can certainly hear the turbo spooling up by then. Which doesnt mean it's creating significant boost at that low rpm - but perhaps my pressure converter is getting pretty tired too!! ;-)

Haahahaha ok true, as for the laboour costs, yes cost an arm and a leg to get the manifold done....are these pressure coverters/actuators (those with the same part number) just as a pain to do as the manifold? ie the EGR one and the one nearest the turbo that activates the plunger to open the vanes?