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Low Boost, Lag? Diagnose the Turbo in your Car, Truck, or SUV

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  1. step : No instructions needed (Feb 26 2020 8:41AM)
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Do you have a turbo vehicle that's just not performing the way it usually does? We're gonna go over some of the symptoms and repairs to get it back on road working normally.

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To really understand what could be going wrong with a turbo, let's locate it and check it out. With the turbo still in the vehicle, you can start by checking the play. You wanna grab some needle nose pliers and just grab the center of the compressor wheel and if you move it in and out, you shouldn't feel any play there. And this one definitely has play. And then you can check the side to side. If the compressor wheel is rubbing up against the side of the turbo body, that's not good either. Another thing to check, if you have excessive oil on the blades themselves, that could be because the seal inside the turbo is bad, both on the turbo compressor side or on the turbine side. If you see excessive oil burning in there then the turbo needs to be replaced.

I'm gonna check the wastegate operation with a vacuum gauge and hook up the vacuum gauge right here. And set this down, make sure the diaphragm's working. As you can see, it moved the actual wastegate itself. And release the vacuum and it goes back, which is good. So this is moving properly, which is nice. None of these parts are serviceable so if this was frozen, or generally they're not serviceable, then you're gonna have to replace the whole turbo assembly.

Now let's take the turbo off the vehicle to get a closer look. One of the symptoms of the wastegate not working or if this was slammed closed, your turbo's gonna build up too much pressure. It's gonna spin too fast. The car will go really fast and you're probably not gonna know why. It's probably because that's stuck closed. Or, if the opposite happens, if this valve gets stuck open, it's not gonna build any pressure and then the turbo's not working. So that's something to check out.

This is the diverter valve. This is electronically controlled. When this valve gets stuck, there's gonna be excessive pressure on the intake side of it. So basically what this valve does, when the throttle body closes, like if you're accelerating and then you let up on the gas, this valve opens up because there's too much pressure in the intake and it diverts the pressure. So this is called the diverter valve, blow-off valve, or BOV.

And now if you take this diverter valve off. This valve get stuck or broken. Sometimes these break right around here, then you're not gonna have any boost either. So it's a good idea to check that.

Now we can take the turbo apart further. You wanna make sure all the intake hoses and even the pressure side of the turbo where it pressurizes the air and it goes into the intercooler, make sure all that ducting and hoses are secure. If any of those pop off, that can cause an issue.

Here is the turbine side or the exhaust side. The exhaust gases go by this turbine, spin it, and over the compressor side where this fan will take the fresh air, pressurize it, and send it into the intake. And that's how you get your boost. If you couldn't see it before when we were checking to see if there was any play in this turbo, any play in the fan, what we're checking is the in and out play, going up and down like this. It's still kinda hard to see, but there's definitely some play there. You can hear it when I go back and forth with this. So that's the shaft going back and forth in the center there.

Another thing to look at, you can take off the intake snorkel and check the blades. See if any of the blades are broken. If any of those are broken, then that's not good. They're gonna end up in your engine and you're gonna cause even more damage. Same with the exhaust side. If you take off either an O2 sensor or you might even have to take off a pipe and you see any of these broken, that's not good.

If you're checking the turbo and you go to spin it, and it doesn't spin, obviously it's no good. And then if you spin it and it makes a lot of noise, you hear a lot of bearing noise or grinding or something, then the turbo's not gonna be good.

If you see any part on the intake side of where the turbo is and you see where the turbo fan has actually contacted the sidewall, then that's not good. You definitely don't want any contact there.

So our turbo definitely had some issues so we decided to replace it and get our performance back. I hope this video helped you out and you learned something about the internals of how the turbo works and the possible problems with it. Now that'll help you get back on the road and your turbo working to its full potential.

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