Diesel Engine VGT Turbocharger Failure Diagnosis

You've probably heard a lot of bad things about variable geometry turbochargers by now. We all havethey break easy, they're expensive, they're complicated, etc. But actually, when your turbo fails, it's often an indication that something is going wrong somewhere else in your engine.

Think your VGT turbo is too much trouble? Learn why you shouldn't delete EGR system!

We get people asking questions daily, like, "How do I know if my variable geometry turbocharger is bad?" Well, we're here to dive into what might be giving your VGT trouble. 

We also discuss this in our video:



If you're looking for a replacement VGT for your diesel engine, we've got 'em! Our ASE Certified Technicians will help you find the right turbo!

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What Can Your Sector Gear Tell You About Your VGT?

If you think you're having problems with your diesel engine VGT, one of the easiest things you can do is take a look at the sector gear. This requires having the actuator off, but once you've done that, you can take the sector gear and move it by hand. It should actually move quite a ways, if everything is working properly. 


vgt turbo failure diagnosis stop to stop | Highway & Heavy Parts


There's a dimple in the housing sector, and it should run right down to that. In the image above, we put the Holset guide on it, and it should run from green mark to green mark, which lines up with that dimple. This particular one only moves about a third of the way. This means it has some damage going on in the inside. The next step is to take it apart and see what's going on inside. 


vgt turbo failure diagnosis stop to stop measurement | Highway & Heavy Parts


For reference, the above is just the center housing. To give you an idea, the sector gear on this one will move from green mark to green mark effortlessly. So just what might be preventing this sector gear from moving as it should? It might be an issue with your shroud plate.

Proper installation can help prevent issues down the road. To find out about installing a VGT properly, read out post, Guidelines for Diesel Engine VGT Turbo Installation


Is Your VGT Shroud Plate Damaged? 

As we mentioned, problems with the sector gear indicate issues within the turbo itself. Taking apart the turbo lets you really see what makes it tick, as well as allowing you to find the source of your problems. All the working components of the turbo are going to be on the exhaust side. When you pull it out and flip it over, that's a completely assembled unit. Once it's been removed, it should move from stop to stop.

What was happening in this particular example was due to the shroud plate. Looking inside the exhaust housing, you see the shroud plate. This is what the fins actually travel through. 


vgt turbo failure diagnosis shroud plate | Highway & Heavy Parts


The image above shows you where the shroud plate is located within the turbo. The shroud plate is actually inside the exhaust housing and the fins travel through it. 


vgt turbo failure diagnosis damaged fins | Highway & Heavy Parts


In the one pictured, we can see that it has some damage to it. So, if your shroud plate is all the way in and you get a bent fin, that fin will not travel through the plate any more. That's what's going to give you problems. 

This is what happens with a lot of these VGTs. You get might get carbon, or debris, or coolant contamination, or you might even get contamination from your EGR system. There's a lot of reasons why, but they all spell trouble for your VGT turbo.

Curious about other problems you might be having? Check out our blog on other VGT turbo issues!

If you need help with your diesel engine VGT, we've got service topics that come with all our turbos to make sure that yours will last for another million miles!


Have you experienced a failure in your diesel engine? Our ASE Certified Technicians can help you get the parts you need to get you back up and running! Give us a call at 844-304-7688, or request a quote online!