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What to worry about when buying a USED TURBO

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JusMX141

Moderator
15,152
1,268
Dec 13, 2005
Greensburg, Pennsylvania
Everyone's been in a position where they come across a hell of a good deal on a used turbo. There are a series of things you should look at before you buy.
  • Shaft play. This determines how well a turbo has been lubricated. There should be NO noticeable in/out shaft play (less than .002" by measurement), and as minimal up/down shaft play as possible (less than .014" on most turbos).

    On a journal bearing turbo, the bronze journal bearings ride on a film of oil so if the turbo has sat off the car for a while, the oil has drained away from the bearings. You should turn the turbo upside down and pour a small amount of motor oil into the oil drain flange and allow it to flow into the journal bearings before you get a final measurement of up/down shaft play.

  • Bad oil seals. If you look at the turbine wheel and it appears WET, the turbine shaft seal is bad. It is more common that the turbine shaft seal will leak before the compressor seal because of the extreme temperatures the turbine seal sees. The most common killer of oil seals is excessive shaft play.

  • Damage to the turbine or compressor wheel(s). It is more common for there to be damage to the inducer of each turbine than the exducer, so be sure to examine both wheels very well. Remember- the inducer of the turbine wheel is only visible by peering into the turbine housing inlet (the flange that mounts to the manifold.)

  • Exhaust housing cracks. Most cracks appear on the interior of the exhaust housing. Usually, these cracks are from the rapid heating and cooling that the housing sees, and they generally will not effect performance of the turbo. However, if cracks are present, be sure they aren't the whole way through where the housing will leak or cause the wastegate flapper to not seal properly.

  • Check all of the mounting holes for stripped threads or broken hardware. This is pretty self-explained.

  • If possible, check the wastegate actuator for smooth operation and make sure the flapper seals tightly against the housing. I test the actuator of every turbo I rebuild by applying 20psi into the hose nipple with a rubber-tipped blowgun. A Mitsu actuator has about 1/3 of the travel that a Garrett actuator does, so don't be surprised when the flapper of a Mitsu turbo opens less than 1/2 inch.



A few things to remember:
  • Don't bother asking mileage. Many times a turbo with high miles that was well cared-for will be in better shape than a turbo with low miles that was abused. You will know how well a turbo is cared for if you check it with the steps listed above.

  • Ask the owner for the history of the car that the turbo was removed from. If the turbo has just been pulled from a car with a blown engine, STAY AWAY! The inside of that turbo is so full of metal that it won't last 20 miles.

These are photos of a thrust plate that were taken from a Bullseye T04B V-Trim that had very low miles but came from a car that blew the engine with the turbo installed. Well, see for yourself:

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The thrust plate is totally loaded with shavings.

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Here is the V-Trim's thrust plate next to a new T3 thrust plate. You can clearly see that the oil passages are totally clogged. The journal bearings didn't look much better.

Thanks for reading my post, and feel free to add any info from other personal experiences!
 
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Great post.
Hopefully it helps people out in the future. Sometimes the problem is being able to see the turbo in person. Which in fact tosses all these tips out the window.

I can say, if you're planning to buy a used turbo from this guy you wont be disappointed.
 
I agree 100% and this is why I stay away from buying certain products used and that definitely goes for used turbos . I gave in this time and bought a used HX40 from Ebay and went against this rule like a dope!:shhh: I hope I'm lucky though!:D But I do far from recommend buying a turbo used!:notgood:
 
That is great info if you can visually inspect it. I recently got screwed on a used 20g that was blown to hell. Jsmux hooked me up huge and made the ordeal ok in the end. I can say this I will never buy anything used again over the internet.
 
I must say, most of the turbos I buy for rebuilds are just what I expected....but they're also listed as rebuildable. I've occasionally gotten ripped by buying a turbo that was listed as useable and I expected it to be in great shape, but ends up needing alot of work.

In almost every case that I've had a problem with the turbo that I buy, the seller gladly offers a partial refund to compensate the parts needed because I do all of my rebuilds in-house. The only other option is for them to give a complete refund and try to resell the item for less, so most of the time they gladly offer the partial refund.
 
Great post.
Sometimes the problem is being able to see the turbo in person. Which in fact tosses all these tips out the window.
Very true. My intent was to show DSMer's what to look for if they are buying a turbo and they have the opportunity to visually inspect it.

I suppose this may also work if you buy the turbo from eBay and have paid through Paypal...always inspect the turbo throughly once you get it. If it seems to be blown, contact the seller and say that it is out of spec and needs rebuilt. If the seller doesn't agree to offer a refund, you can always file a Paypal claim which holds their account until a resolution is met.

The most common response you'll get from a seller is "I'm no turbo expert- and it worked fine when I pulled it off the car...." Most of the time a seller reads that "some shaft play is acceptable" when in fact the turbo their selling is completely junk. An unsuspecting buyer purchases and installs it, and within 200 miles the shaft play is so bad that the compressor wheel nails the housing and you're replacing more parts than the turbo is worth.

Never write off purchasing a used turbo completely. Alot of them are in great shape! This thread was intended to educate possible used turbo buyers so that there are less threads starting with "I bought a used turbo and got ripped off!"
 
What is the exhaust housing on the outside of the turbo has a crack...that bad?
 
Great post Justin! This will answer many people's questions in the future and make them more informed buyers!
 
Thanks everyone! Although this thread has been on this site a year and a half now....:D


What is the exhaust housing on the outside of the turbo has a crack...that bad?
Not sure I understand what you mean....it's cracked through the housing completely or just cracked a little around the wastegate hole?

Housing cracks are very common on Mitsu turbos and are practically meaningless unless they go the whole way through the housing. I've seen a new 7cm2 turbine housing crack around the wastegate hole in as little as 5,000 miles.
 
Hi,

Also, if you get a chance to visually inspect the turbo before you buy it. One of the best things to do is take off the compressor and turbine housings and look for wheel rubs. This will help to tell you if the turbo has a shaft play problem or was improperly assembled in the past.

Make sure to mark the orientation of the housings before dissassembly to aid in getting the correct clocking of the housings on reassebmly. Also, I have found that if the turbo is put together in a vertical fashion (CHRA placed into the turbine housing with the turbine housing laying outlet down on a table and then compressor housing placed on top of the CHRA) that it helps with avoiding wheel rubs due to improper assembly. When assembled in the wrong fashion, the housings and wheels can become "cocked" in relation to each other and cause wheel rubs.

Bill
 
Good information my only concern is.

Bad oil seals. If you look at the turbine wheel and it appears WET, the turbine shaft seal is bad. It is more common that the turbine shaft seal will leak before the compressor seal because of the extreme temperatures the turbine seal sees. The most common killer of oil seals is excessive shaft play.

I'm sure this is just because it's old information as I've seen the OP mentioned the correct terminology numerous times on here. There are no "oil seals" on a turbo just gas control rings on both the compressor and turbine side of the shaft. These operate in much the same way a piston ring operates and their main function is to keep the pressure from the turbine and compressor out of the bearing housing. Like piston rings these also have gaps in them which are installed 12 o'clock facing the oil inlet. The GIF below shows you what happens when you have an obstruction in the oil return line such as RTV sealent clogging it, oil level above the oil return in the pan, or excess crankcase pressure.


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Without some serious installer error there's no way these to go bad without the turbo exhibiting some sort of shaft play or binding. We talk to customers on a constant basis that call us with the symptom of oil in the turbine/compressor and shaft play in spec. It's almost always the case is the customers is making 50-100% more power than stock and has completely over looked his crankcase evaporation system and has it either vented or just ran into a sealed catch can. We've seen as little as 5psi in the crankcase cause this to happen so if you're running a catch can and you don't have a vacuum the crankcase pressure might be causing an obstruction in the oil drain line which causes the bearing housing to become pressurized and oil is forced out through the gaps in the gas control rings on the turbocharger.

-Michael
 
Was simply referring to the shaft seals as "oil seals" as that is how 99% of the general public refers to them- although I agree with you 100%...it's virtually impossible for a new turbo or a properly-rebuilt used unit to exhibit oil leakage without excessive shaft play unless the drain is obstructed or the pressure at the inlet is ridiculous (or a combination of the two).

Awesome .gif, by the way- except that's a reverse-rotation turbine being used on a standard-rotation compressor. :p

Sometimes I believe that owners think since the oil enters the cartridge under pressure that it leaves under pressure as well, and that's not the case at all with a gravity drain.
 
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Yeah we just slapped that together with broken parts we had lying around. :p

Good eye though.

-Michael
 
Just trying to get my facts straight here...

So if we are looking at buying a turbo from a previous DSM owner who supplies the oil from the OFH, then the shavings/junk from a blown engine shouldn’t be able to make it to the turbo right? Wouldn’t they be trapped in the oil filter?
 
Once the oil filter becomes clogged with bearing material and becomes a restriction (which is pretty much immediately), all of the engine's oil bypasses the filter entirely. The thrust plate shown above is proof of this.
 
Once the oil filter becomes clogged with bearing material and becomes a restriction (which is pretty much immediately), all of the engine's oil bypasses the filter entirely. The thrust plate shown above is proof of this.

Ah gotcha... I did a little searching and your aren't kidding. I thought it was just a failsafe. The bypass valve in the filter opens up all the damn time.

Some sort of large inline filter is on the to do list for the race car.

The Bypass Value

First you need to understand why the bypass valve is there. Under *ideal* conditions, the bypass valve will *never* open. Because, when it opens, the oil *by passes* the filter and goes on through to the motor, obviously unfiltered. It is a safety valve. However, in *real* operation, it opens often.


One example is when you start the motor when cold. The oil is thick and does not pass easily through the filtration medium, thus building up to a high pressure drop. So, the bypass valve opens to prevent oil-starvation of the motor. How long it stays open is dependent on how cold the oil is and how long it takes to get near operating temperature. When the pressure drop across the filtration medium drops below the bypass valve setting, then the bypass closes. Blipping the throttle while warming up is a good way to get the valve to open and send unfiltered oil to the motor. A steady warm-up rpm is probably a lot better.

Another example can occur when the motor is fully warmed. At idle, the oil pressure is about 15 to 20 psi, and the pressure drop across the filter is about 1 or 2 psi. You take off towards the redline, and quickly build oil pressure to the 70 to 80 psi range. During that full-throttle acceleration the pressure drop across the filter will exceed the bypass setting, and send unfiltered oil to the motor, until the pressure across the filter has time to equalize. During a drag race, shifting through the gears, the bypass will open several times.

A third example, which you should never experience with frequent oil and filter changes, is when a filter becomes clogged. A spin-on filter can commonly hold 10 to 20 grams of trash before it becomes fully clogged. The bypass valve opening is the only way to keep the motor from becoming oil-starved if the filter becomes clogged.
According to Purolator, the Honda OEM filter bypass setting is 12 to 14 psi, and that is how they build their motorcycle oil filter. WIX (NAPA Gold) builds their motorcycle and automobile oil filters with a bypass setting of 8 to 11 psi, while AC Delco builds theirs to a setting of 11 to 17 psi. How much do these differences matter? I don't think anyone knows, even the engineers, and each has its own set of advantages and disadvantages.

If you do lots of racing, you're probably better off with a higher bypass setting.
If you do lots of *cold* starting, especially in the winter, or seldom change your filter, I think you're better off with a lower bypass setting. However, with few exceptions, bypass pressures for spin-on filters run in the 8 to 17 psi range, and any of them should work acceptably.
 
Also make sure your turbine shaft is not bent.

I purchased a rebuilt 14b from a classified source ;) and it blew in 48.3 miles :cry: turns out the shaft was bent so after a few good pulls it made a loud pop and started to pressurize the oil pan. :D

Now i got a good rebuild from justin over a year ago and it is still in perfect condition after 15k+ miles! :thumb:
 
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