Jeff N.

Inspecting a used turbo.

Should there be any up/down play in the shaft? I understand the end play discussion but really have seen no discussion on up/down play. I can't think it's normal but want to check for sure. (Compressor blades show no sign of housing impact)

On a basic teardown, the shaft looks ok (measures across consistently as well, no scores or high/low points) but there is some sort of problem at what I would expect to be the seal on the hot side. There are some sort of metal rings or something that are in pieces.

Will be able to post pics on Monday but wanted to get first impressions now.

Thanks in advance.

Jeff

ArthurPE

shop manual:
radial play is measured on the exhaust side only 0.42 mm max...

makes sense, the bearings are babbitt type and float on the oil...

Chris Prack

There will be more play than you would think is allowable. From what I have seen if it out of spec it will hit the housing on one end or both.

JohnKoaWood

Easy shaft check... roll the shaft on a table and look for the threaded end to wobble back and forth... it will indicate a bent shaft, they can be straightened but it takes some skill...

the seals are split rings, 2 on the turbine end of the shaft, 1 on the collet on the compressor end... these should receive a liberal amount of lithium grease on re-assembly...

as you have torn the turbo down it will need to be rebalanced prior to re-assembly..

excessive radial (side to side play) is a sign of worn bearings (solid bushing type) and can be replaced, there are 2 and they are held in by a pair of snap rings each... the bushing / bearings are brass... and should be a bright brass color... an off color indicates cheap Chinese brass, these wear out faster...

excessive axial (in and out) is usually caused by a worn thrush bearing, or associated part (usually the thrust bearing as it is brass, the other pieces are steel and alloy...) a new thrust bearing should be installed when the turbo is taken apart for rebuild, and is usually included in any rebuild kit...

I rebuilt my turbo... kit was $110 from gpopshop.com ( http://www.gpopshop.com/kkkkits.html )..
and I took the rotating assy to a local shop for balancing ($60) took about an hour... the full rebuild took me about 3 hours of my time, plus balancing... and a few other consumable items (thread locker, lithium grease, assy lube)...

All said and done.. I would pay a shop to do it were I to do it again... difference in cost is roughly $100... but they blast all the pieces clean... a properly rebuilt turbo will look and perform as new... or better (when I had mine balanced, he case hardened the turbine and shaft... I now get boost at 2100RPM, with full boost before 3000 RPM...)

Jeff N.

OK. helpful. I'm out of spec on the radial play but it's not hitting the housing. Next question.

On the cold side, there is a shaft "centering" bushing that goes into the shaft housing. (This does not look like the load bearing). This bushing is a bit loose in the back plate housing and there is bright wear on the housing where it moves.

It looks like part 8 is loose in part 12 in this picture. Part 12 is worn. How serious is that problem?

JohnKoaWood

Part 4, 7, and 8 form the rotating portion of the thrust assy, and sandwich the thrust bearing (part #5, part 6 is an oil diverter)... with the nut off and shaft out part 8 will move.. as it just sits into part 12... and is sealed with another split ring like on the turbine shaft end...

the nut on the end torques the compressor wheel against part 8, which in turn torques against part 7 which in turn torques against part 4 which torques against the turbine shaft...

4 is a washer, 7 is a spacer, 8 is the collet seal on the compressor end...

does that make sense?

no reason to worry about light wear in part #12.. as long as new bushings (part #1) resolve the axial play issues, and the entire assy torques down properly..

Jeff N.

Very helpful. I think it's all good.

I'll see if I can post some pics to just add some color to the thread.

superloaf

so there is a noticeable difference in performance with your's once it was rebuilt?

also, how exactly do they balance the turbo? is it just a matter of rotating the turbine until it balances out?

Jeff N.

Here's a few pics from the used unit.

Should be a K27/7200 compressor wheel. Look like one? Leading edge of the compressor blades have some impact marks...bad air cleaner?



Backside showing balancing marks and where material has been removed.





Here's the cold side housing. You can see the slight wear in the bushing area. John, after your description, this doesn't seem to be a problem.





The shaft. You can see what's left of the seals hanging on the shaft. There is also some very slight scoring on the shaft. In this area the shaft mics out about .001 under the rest of the shaft. How serious is this do you think? You can see the wear on the coldside but it's smooth.

JohnKoaWood

Yes there is a definite difference... during balancing / cleaning before he also case hardened the turbine and shaft...

You balance the turbinge first, it gets spun on a turbine balancer at high speed with a strobe light illuminating the imbalance... the operator marks it with different marks (see pics) to keep track, and then grinds off material to make it within the balance spec...

then the same is done to the compressor wheel, mounted on a precision mandrel, then the compressor is mounted to, and torqued onto the turbine shaft... and the entire assy is balanced... then marked to ensure it is CLOSE when re-assembled into the center section...

SOME also balance it after it is mounted into the center section... and grind away the nose of the compressor wheel to ensure the entire thing is balanced...


Nah, that is OK, it could be cleaned up, or left as is..no real worries there...

Yup, that is the marks put on during balancing, and the grind spot is the operators work at balancing the wheel...

Again, no worries here, as long as the new bearings take out the slop, and there is not grooves worn in, or holes WAY out of round..it should be fine... if not, let me know and I'll send you my second center section... it is dirty, but looks almost new

Seals look dirty, but normal oil cokeing...... IF you take it to Tim for balancing or rebuild, he will clean up the shaft on a lathe for you... and he will SS shot blast the parts to get em clean... his shop is awesome, and he definitely knows what the hell he is doing... has the KKK tolerance specs on the wall right by his balancer, and has a two pocket folder full of turbo torque specs... old school, but effective...