cm870 ISX Turbo Screech Monroe/Charlote, NC

[Magnum1]

Hello group. I've tried attaching the video, mov file, but, " The type of file that you attached is not allowed. Please remove the attachment or choose a different type"

which files are supported? - as that might help a little to have a video.

I have a turbo that started to screech after truck was idling overnight. I can move the VG crank up, with pry bar, a little, when idling, and the screech goes away. It also only makes the noice when at operating temp's. It makes the noice when idling or driving, after motor warms up to operating temp.

Any of you guys know anyone that you can recommend in that area that can look at it and/or have the proper software with hardware for remote diagnosis? all the help would be appreciated.

Thank you.


Video's are in the Facebook group as well, if you can view them for reference:

https://www.facebook.com/100005801835976...071651672/
https://www.facebook.com/100005801835976...076910466/
https://www.facebook.com/100005801835976...602929413/

[Rawze]

can't see the video.. says not available. However ...

some people will describe the screeching sound "like letting the air out of a metal baloon".. or "sounding like it is scraping the housing at high speed".


Turbo screeching is 95+% always caused by the turbo mounting gasket failing (or an exhaust manifold gasket failing) and not the turbo itself.


Check that the torque on the 4 mounting turbo bolts is correct. On a CM870, this would be 74 ft-lbs for a 500-series turbo.


Also check the exhaust manifold and check all the torque on the bolts. They are supposed to be 45 ft-lbs. Any missing/snapped manifold bolts will cause it too.

If it still screeches, then the turbo mounting gasket has gone bad.

[Magnum1]

what format can I use to upload a video? - because if I'll lift the vg crank up just a little bit, the screeching goes way .


here is a youtubevideo that seems like duplicating the sound itself/

https://youtu.be/9nF7fiIH-18

[Rawze]

(04-07-2023 )Magnum1 Wrote:  what format can I use to upload a video? - because if I'll lift the vg crank up just a little bit, the screeching goes way .


here is a youtubevideo that seems like duplicating the sound itself/

https://youtu.be/9nF7fiIH-18

yup ... sounds like the turbo mounting gasket to me.

[Bengy88]

What Rawze said all day long, turbo gasket or manifold gasket. 90% of the time you will have a broken bolt and occasionally a cracked manifold or turbo housing.

[wrenchwabbit91]

i had this problem on an 870, turned out to be the pressure regulator in the vgt controller. i would check what the others have posted first, i think the controller was $1200... the ecm was commanding 70% to the actuator but it was maxed out at full air pressure.

[Rawze]

(04-07-2023 )wrenchwabbit91 Wrote:  i had this problem on an 870, turned out to be the pressure regulator in the vgt controller. i would check what the others have posted first, i think the controller was $1200... the ecm was commanding 70% to the actuator but it was maxed out at full air pressure.

even a bad actuator will not cause the turbo to squeal.

[Magnum1]

Thank you everyone for your replies. If I will come to the conclusion that it is either vgt or controller - it'll have stationary turbo.

[Magnum1]

(04-07-2023 )wrenchwabbit91 Wrote:  i had this problem on an 870, turned out to be the pressure regulator in the vgt controller. i would check what the others have posted first, i think the controller was $1200... the ecm was commanding 70% to the actuator but it was maxed out at full air pressure.

were you able to watch the videos that I have on Facebook - it does look like the vg actuator could be pushing the vg crank little further than it should, maybe, as when I ouch it up with the pry-bar, noise stops.