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Old December 23rd, 2005, 17:36   #1
gt
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Question Turbo shaft play-HOW MUCH should there be?

I am overhauling 98 TDI & the turbo it has ALOT of shaft play. The car would not pull over 3000 rpm. The last time I drove it. Engine had alot of blowby. Intake was really clogged up. The car seemed like it was not taken car of maintiance wise. Need a little help on the turbo play. Have not seen one worn this bad. gt
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Old December 23rd, 2005, 19:22   #2
John C
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Turbos are usually a binary device when it comes to the bearing system. They are usually broke or not .

That said, you should have only slight - .002 - .004 axial play. More indicates thrust bearing damage and worn piston ring seals on the shaft, which will lead to higher blowby from the turbo (and probably a failed turbo). Radial play can be more so long as the wheels do not touch the housing. I haven't worked on TDI turbos specifically, so I can't be more specific. If you find any rubbing, you willl need to get a rebuilt turbo which ahs been remachined to accommodate the worn parts. Turbos are VERY sensitive to clearance gaps when it comes to their efficiency. I'd expect .010" or less clearance along the contours in the compressor and turbine stages of this size turbo.

Turbos are dynamically balanced, so if you take one apart, note the relationship among ALL the parts and get it back together in the same alignment - and don't bend the shaft . Shaft may have left hand thread, check before you wrench!

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Old December 23rd, 2005, 22:36   #3
dareo
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Replace your turbo. I never checked mine, it broke, sent oil into my engine, now i'm rebuilding the engine and had to buy a new turbo. The whole engine rebuild part could have been avoided. My
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Old December 23rd, 2005, 22:36   #4
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...My new turbo has zero movement aside from spinning. Absolutly nothing that i can feel. If its wiggling a lot you should change it quick.
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Old December 24th, 2005, 10:40   #5
Drivbiwire
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Quote:
Originally Posted by gt
I am overhauling 98 TDI & the turbo it has ALOT of shaft play. The car would not pull over 3000 rpm. The last time I drove it. Engine had alot of blowby. Intake was really clogged up. The car seemed like it was not taken car of maintiance wise. Need a little help on the turbo play. Have not seen one worn this bad. gt
Your issue is more than likely not related to the turbo in any way.

Sounds like an engine that has been babied to death.

More than likely you have a jammed VNT, jammed compression rings, clogged intake, bad N75.

This sounds like an engine that has been shifted in some bizarre attempt to "Drive like a diesel".

More specifics are needed, what model do you have? There were two versions of the TDI sold in 1998 so we have no idea what car you are talking about.

Again your turbo shaft play is something you really should not worry about, it's supposed to be there and there is a significant amount needed based on how these turbos are lubricated and supported in the bearing housing. Guestimating the end play(radial) is around 1-2mm in a brand new turbo on a VNT-15 in the ALH and about the same in a K03 in the AHU. Axial is very little so that the seals do not make contact with the spinning portion and cause damage.

DB
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Last edited by Drivbiwire; December 24th, 2005 at 10:46.
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Old December 24th, 2005, 15:25   #6
John C
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I'd respectfully disagree with DB . I've looked at several thousand failed/returned for rebuilt thurbos, albeit 'heavy duty' Diesel engine size . We did these teardowns to assess failure trends and modes, thus my statements in my previous post. Axial play must be closely controlled to keep the shaft seals from wearing. Perceived radial play must not be so much that the wheels can rub their respective housings.

I'd suggest you push on the shaft radially, and see if you can get the impeller of turbine wheel to rub their respective housing. If you can't, the turbo is likely OK. Remember, the turbo at full boost is turning some 160K RPM and driving about 3 HP across the shaft, so there is some significant forces generated within the turbo.

Turbos this size are typically dynamically balanced to within .001 in-oz. Even so the imbalance forces at speed are not onsignificant.

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Old December 24th, 2005, 16:02   #7
Drivbiwire
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Per Garrett:
Quote:
GT-15
Axial End play:
Minimum: .001"
Maximum: .003"
Eccentricity:
Maximum: .0004"
Radial:
No Min/Max specified (no contact with housing allowed)
Balance:
0.65G entre 0 - 90.000 rpm
2.0G entre 90.000 - 168.000 rpm

VNT-15/GT-15V/VNT-17
same limits as specified above
Balance:
0.6G entre 0 - 90.000 rpm
3.0G entre 90.000 - 168.000 rpm
DB
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Last edited by Drivbiwire; December 24th, 2005 at 16:11.
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Old December 24th, 2005, 18:36   #8
vazjetta
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I have a 1999.5 Jetta TDI ALH. I have installed many new parts in the last few months. The vehicle has 122,000 miles on it. I'm getting ready to spend anohter $600 in parts and tools for the timing belt and H2O pump. I'm wondering is I should be concerned with the turbo. I have read through the threads that the turbo will hurt the engine when it decides to got bad. Can anyone clue me in about at what mileage that it should be replacing the turvo and if there is any maintence I should be performing to the turbo?

Thanks in advance for your help.
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Old December 24th, 2005, 18:44   #9
whitedog
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The turbo is a prescision made part with human error that will happen. it may last 100,000 miles it may last 300,000 miles. use a good Synthetic that you can find int he fuels and lubricants section on your own and sleep well and drive with an open mind.
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Old December 24th, 2005, 19:36   #10
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Can someone define axial play?? The last time I had the intake off my Jetta I checked the turbo (as much as i could). Reaching through the inlet I was able to push and pull the shaft with noticeable movement. I was just hoping that I don't have to replace the turbo yet.
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Old December 24th, 2005, 23:40   #11
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Old December 25th, 2005, 08:45   #12
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Only ballbearing turbos will have no radial play, all others *must* have some amount of play. Normal turbos have hydrodynamic bearings, and these must by definition have play, to leave space for the oil layers...

In the likes of the T3, as boost is increased so does endthrust. This thrust causes wear on the thrustbearing to the extent that modified 360deg bearings are used in modded applications to improve longevity.

As JohnC and DB say, axial play is the critical one. As an example, Toyota offer only a value for axial play as the pass/fail condition on their CT series turbos....
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Old December 25th, 2005, 09:03   #13
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DOH.

I think that I need to start saving for one of those vnt-17s that Kerma has.
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Old December 25th, 2005, 13:44   #14
John C
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Well, I was close! My experience is with Holset turbos, but so long as hydrodynamic bearings are in use, the different manufacturers spec's are pretty similar. Also, I've worked with turbos for displacements starting at 3X the TDI, so it makes sense the end float would be reduced.

Only comment I would maike regarding thrust bearing loading is that the manufacturers try to balance the load between the compressor and turbine stages to minimize thrust loading. Loading does occur during transients, e.g. turbine loading under acceleration, and compressor loading during decel.

Turbos should last the life of the engine. If you are having to overhaul the engine, I'd have the turbo overhauled as well. It could be as simple as new bearings and seals if you are lucky, or more extensive rework if you're not

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Old December 25th, 2005, 15:53   #15
vazjetta
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Can turbos be rebuilt or is it better to replace new? I'm not complaining about spending money, I just don't want to loose the motor over a $900 part if I can prevent it, on the other hand I don't to spend $900 dallors if it's a part that I can service and extend it's life.
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