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-   -   No boost - Caused by vac leak? (http://d24t.com/showthread.php?t=1880)

monkeh 07-10-2018 08:21 AM

No boost - Caused by vac leak?
Just picked up a 940, feels very underpowered for a d24tic.
Ive noticed a LOT of perished vac hoses apart from the one on the wastegate actuator. I have no boost, I tried moving the wastegate actuator but the spring is too strong for me to move.
Before I begin pulling apart the turbo or book it in to be looked at, Will any vac leak render the turbo boost defunct?

v8volvo 07-11-2018 08:41 PM

The D24TIC turbo may be different. But for the D24T turbo and most other wastegate type turbos, the hose to the wastegate carries pressure instead of vacuum, providing the force to open the wastegate when the spring is overcome. Thus if the hose fails the result is too much boost rather than a loss of boost. No boost would more likely be a stuck open wastegate or actuator, or something else.

If the turbo on the D24TIC has an external wastegate and actuator with a rod you can see, then one thing you could check would be to take off the clip where the actuator rod meets the wastegate arm and separate them, then try moving the wastegate arm and see if either it or the actuator is frozen. The actuator spring is strong but usually you can move them at least a little with some finger pressure.

Fuel and air filters would be good to check also. If either one of them is restricted the symptoms can mimic a turbo problem. Both are cheap so if in doubt, always worth a try replacing them and see if it makes a difference.

monkeh 07-12-2018 01:42 AM

Replaced a boot load of vac lines and concluded it is the wastegate actuator is jammed. Just need to wait for cold engine before I get my hands in there...

monkeh 07-21-2018 01:08 AM

Pulled the turbo, no physical jams, Removing the actuator circlip the wastegate is free, Yet was running with minimal boost before.

Replaced with another used one from my 760, Fighting with the oil feeds to mount the banjo's.
Now, it goes like a scalded cat, sounds totally different, yet side by side the turbos are identical, Its now back to being a d24tic I remember.

ngoma 07-21-2018 12:22 PM

So your orig. turbo needs rebuilding?

monkeh 07-21-2018 10:13 PM

Yes, Digging further in, It appears the bearings are not as free as the replacement.
There is a good buildup of soot, either before or after bearing issue, Its goosed. I did before replacing this, spray everything with plus gas thinking it was a stuck wastegate and drive it exceptionally hard, I was managing to build boost slowly at 3000rpm.
Engine is at 298k, Wouldn't be surprised if this turbo wasn't that far off same mileage.

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