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#1
11-26-2018, 03:35 AM
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thank you for your reply..
I questioned that with my mechanic and he said it was a wastegate?!! I asked him if it was variable but he was quite adamant its a wastegate. I believe that is the part that has been changed yes it controls the plunger on the side of the turbo and moves it in or out about 12mm. we hthought it was this as the plunger was previously moving slowly due to the soot build up on the filter of it due to the manifold leak..... 
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#2
11-26-2018, 03:59 AM
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Quote:
 The vacuum actuator does move a rod (a plunger) but it opens and closes a set of direction vanes inside the the turbine, called a nozzle ring. This nozzle ring CAN become fouled with carbon - although this is not likely to be the result of a cracked manifold.  I've very recently replaced my cracked manifold (on my 2005 M57TUD30) and I checked the vacuum actuator etc prior to putting it all back together.  See this post.... https://xoutpost.com/1142332-post39.html There's a few items in the vacuum system that need checking and the pressure modulator is the first thing I'd check, if you haven't yet done so. I've dealt with similar symptoms on a turbo diesel engines in the past and this pressure modulator was the fault. Not saying your is, but you'll want to verify it is working correctly. You'll also need to confirm you have no boost leaks in the intercooler pipework etc. Diagnosing issues like this can be very tricky - I hope your mechanic is very experienced with BMW turbo diesels... 
__________________
Wayne 2005 BMW X5 3.0d (b 02/05) 2001 BMW F650GS Dakar (b 06/01) 
Last edited by wpoll; 11-26-2018 at 04:00 PM.
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#3
11-26-2018, 04:09 AM
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hi thanks I'll check that post out now,
I was concerned that a flake of metal was missing from the inner skin of the manifold at the point at which it would meet the turbo probably about 10x13mm but he said he had checked the turbo for damage and it wasn't and it all span freely and all was ok ... I'm now thinking is this piece jammed in the nozzle ring somehow... it is however boosting hard when all is well and at them moment I only feel the loss of power top end and the howl when cold and at idle when the vacuum hit -18 also vacuum hoses have been replaced and apparently intercooler and exhaust checked for blockages/leaks. my gut feeling is that it the turbo and I'm really fed up as I only changed this about 3yrs ago / probably 28,000 miles! and also if it is it could have been replaced easily and with the same labour cost as when the cam cover was off and the manifold out! Last edited by Clunk84; 11-26-2018 at 04:22 AM.
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#4
11-26-2018, 04:39 AM
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Quote:
 If there is a piece of manifold missing, then where is it? It sounds too big to have passed through the turbo... You might be right about it jamming the nozzle ring, although if the nozzle ring was jammed the actuator rod (plunger) wouldn't move. That's the exact reason I changed my manifold as soon as the cracks started - they are known to fall apart if left too long.  In my vacuum test, it took about -15psi on the VGT actuator to move the actuator to it's full limit. My measurements weren't exact but it all works very well. I wouldn't think -18psi would be an issue. In fact too much vacuum in itself cant cause any issue, as the nozzle ring will just hit an end stop and not move any further. What CAN cause issues is too much vacuum at the wrong time. And the amount of vacuum applied to the actuator is only controlled by the pressure modulator, hence why I think it needs to be checked out. The vacuum supply is from the vacuum pump, via the main vacuum manifold, to the vacuum reservoir through the pressure (vacuum) modulator and then to the actuator. The correct way to check this system is to check the DDE for errors related to charge pressure control deviation. Any errors noted should be followed as per the diagnostic steps provided by BMW. There's some ore info. on turbo issues here... https://www.newtis.info/tisv2/a/en/e...ntrol/EIDTjVEl and here... https://www.newtis.info/tisv2/a/en/e...ntrol/EIXiL8xM HTH...
__________________
Wayne 2005 BMW X5 3.0d (b 02/05) 2001 BMW F650GS Dakar (b 06/01)
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#5
11-26-2018, 05:11 AM
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at the moment I have rigged a vac gauge inside the car and if I defeat the check valve installed (block it) the vac increases to -18 to -20 and at that point you can hear the turbo start to howl then when you drive the car is very sluggish upon accelerating and the vac bounces/stutters a little and the car matches said bounce until it manages to get to about -14 and then it takes off and pulls hard with the vac dropping off to near zero at high rpm. its like the solenoid valve cant release when the vac gets that low... it would be interesting to find out what the actual vac pressure should be but I can't find the value noted anywhere.
where about physically is the pressure modulator you mention? I'm sorry for all the questions but with short daylight hours and work its a real pain to get anything done at the minute. thank you for all your help 
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