What To Look For When Buying A Used Turbocharger

Published by Tim Scott on Mar 16, 2016

Used Turbocharger? Buyer Beware!

Buying a used turbo might seem like a good deal at the time, but that purchase might cost you more than you think. There could be hidden damage deep inside caused by excessive wear, ingestion of foreign objects, debris from damaged engine parts, overheat/over-boost damage and more. You may not know the damage is there without disassembly and careful inspection. In this video we show you the types of damage to look for and what to avoid.

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If you have a used turbo that you’re not sure is safe to install on your expensive engine, or your old turbo is simply worn out and no longer delivering the power you need, contact us today!

Transcript

Hey everyone. Thanks for coming back to Tim’s Turbos. I want to do a crash course on buying a used turbocharger.

I’m going to start from the compressor end all the way to the turbine end on things you could look for to see if you want to decide if you actually want to buy it or not.

Check for Shake Problems

The first test – and the simplest test – is to pick up the turbocharger and shake it. If you have a shake problem and you see the wheels flopping around in there, and the turbine and compressor wheel don’t rotate at the same time, the best thing to do with this turbocharger is put it in a nice box and throw it in the trash.

Inspect the Compressor Wheel

The next step is the compressor wheel inspection. If you have any type of bearing failure, you’re going to have a compressor wheel failure most of the time too. If you look here, you can see the blades actually roll upward.

This is from the wheel going back and forth contacting the housing. This can also be a soft damage issue. If you pulled in like a shop rag or a silicone coupler from your intercooler, it’ll also roll those blades back and not snap them off, but usually you’re going to have some shiny marks here like a polishing.

The best way to fix this one if it’s got a lot of in-out play and a lot of shaft play and probably has some bearing damage is to throw it away too.

Check the Edges of the Compressor Wheel

Now, there are some other pieces you can fix on compressor wheels. This is a regular HX35 wheel.

It’s probably hard to see in the picture, but you can kind of listen. It has a bunch of grooves and chips on the front of the face. You can reface these and clean them up. Compressor wheels aren’t too expensive depending on which one you get, but another thing you want to look for is on the very edges. You should feel a smooth edge with your thumbnail coming off this corner here. If you feel any kind of click on it, that means the wheel has been contacting the housing. The best thing to do with that is throw it away.

What In-and-Out Play Does to a Turbocharger

Next off, I’m going to show you what in-and-out play does on a turbocharger.

Most bearing designs can withstand some side-to-side play from left-to-right or up-and-down, but when you have an in-and-out play – if you look at the piston ring right here, which is stationary – the piston ring doesn’t move, but the shaft comes in-and-out and that cuts the groove on the shaft.

Usually you’re going to start developing oil failure, it’s going to go past the edges and the compressor wheel is just as bad. On the turbine and compressor side on the inducer of the turbine, you’re gonna see wear and back behind the seal play you’ll see contact in there. On the compressor side, you’re going to see damage right on the bottom of the exducer because the wheel is going towards the compressor cover.

There is not much you can do to repair that and you’re best off getting new parts, but externally, visually you can’t see in-and-out thrust damage because everything is underneath the surfaces, so you really want to be careful of that.

Check for Turbine Damage

Another thing: there are no two-piece turbine shafts and heads. If this happens, something snapped off the fusion weld. The only thing you can do with that is throw them in the trash or go to a scrap metal dealer and get some money.

When you snap off a turbine head, it may not look that bad, but this contour has been all chewed up right here and so when the wheel bounces in there and snaps the head, eventually it will actually blow through and that will be your catalytic converter if you’re running one and this turbine housing is pretty much worthless.

Externally, the bore looks about the same, but when you go to the inside that radius is so far out you can have a quarter inch gap between the blades and the turbine wheel. So that turbine housing is pretty much trash.

Look for Surge Problems

Another thing to look at is surge problems. This wheel could have failed from two different things, overboost causing the surge. On this one, the lock nut popped off and sucked back in. You can see little pockmarks right on the inside of the bore. That’s just the wheel bouncing back-and-forth chewing everything up.

If you’re lucky, sometimes you can salvage this; most of the time when the lock nut comes off through all the thrust compartments don’t have any load anymore, so all of them expand out and you start running into the turbine wheel hitting the housing and stuff like that. So, you might be able to fix it with a cartridge as long as the housings are still in a good condition, but you just have to take a closer look at it.

Signs of Side-to-Side Damage – Check for Shiny Marks on the Turbine Edges

Another issue is when you have a side-to-side damage, you’re gonna see shiny marks on the turbine edges right where it hits the bore. Same as a compressor wheel, you will feel a tick right there your fingernail. If you feel any tick, it’s had some type of contact. Some people will say that the wheel isn’t contacting the housing – that’s just because the wheel has all worn off all of the edges that actually touches the bore.

Blown Piston Rings

Another set – something you can’t see when you have a turbo all assembled – this turbocharger failed from blown piston rings. So the rings fed into the turbine wheel itself and you can see where it just buckles them over and shreds it. Sometimes you can fix these with just a turbine wheel as long as you didn’t bang the shaft up on the inside where it goes through the bore. It’s a toss-up, but if you can take the turbine housing off of a turbocharger before you buy it, then do it. You can read a lot of information on this.

I run into this a lot from high-performance motors that run too lean. The most popular one is probably a 7-3 Powerstroke – the glow plug tips break off when they go through and you can’t see the turbine wheel underneath until you take the turbine housing off.

Check the Bore and Wastegate Ports for Cracks

This is a good example of a turbo that doesn’t look too bad, but you have in-and-out play. You can kind of see the blades rolled back in the contact there. This just has a little bit of work and it can be a salvaged by a cartridge rebuild. You want to take a look in the bore to see if there are massive cracks. Most of the cracks you are going see around the wastegate ports here because the heat transfer is very a radical and it goes up and down. If you see broken studs, figure about $20-50 per stud on any turbocharger rebuild and if it’s stainless steel housing, it’s even more of a headache. If you don’t have a mill or some type of bolt cutter to cut those out, you might as well buy a new turbine housing.

MAP Groove Cuts

Another thing to look – this one might be hard to see – is MAP groove cuts. Right on the edge here, you can kind of see how there’s a step that feeds in and disappears when you move the wheel to the side. That’s where the map groove is and so it had too much shaft play and bearing damage that it contacted everywhere else but the MAP groove. That wheel’s toast. The turbo is completely rusted together, the wastegate is rusted, and the best thing to do with this turbo is throw it in the trash.

Uneven Bore Wobble

Here’s another thing you may not think about: when you have a turbocharger that has been on a car for a couple hundred thousand miles, this shaft and the wastegate port has opened a couple million times probably and it starts to get uneven bore wobble at so that the cut in the bore there has actually oscillated and turned into an egg shape. A lot of times it’s not a big issue, but if it closes all the way and then you still have a lift up on the wastegate port, then there’s not much you can do with the housing and you sort of press the bushing out and weld in a new one, well a new shaft on. You’d probably be better off finding a new shaft.

Unseen Turbo Damage

Last but not least: unseen damage. Just about every 911 turbo I build I have to put in a new turbine shaft just because they erode away.

Up here there is a piston ring groove on the bottom and an external groove. The external groove just gets rusty and carbon buildup and it starts to cut away. When you put the double piston rings on there and try to pop it back into the bore, you’re pretty lucky if you get it filed back in. Most time they pop back off and slide over the shaft, so you’re best off replacing the shaft on all of that stuff.

You can’t see these damages until the turbo is completely disassembled, so one thing you have to look out for is if you’re buying a turbocharger that’s used, make sure you don’t see any signs of wear. You shouldn’t see any shaft play, any in-and-out whatsoever, very minimal side-to-side, there’s always going to be some, but keep an eye on the different things.

Conclusion

We can rebuild pretty much anything, but to try to keep the cost down, use the best kind of route to go with instead of bringing it in and letting somebody check it out.

I hope this video helps.

Thanks a lot.

-Tim’s Turbos