Turbo clearances

[RED60]

I've got my eye out for a 2nd hand turbo. What I wanna know is, what is an acceptable amount of shaft play and end float. Every 2nd hand one I've checked has had a noticeable amount of both. So what do they have NEW and what is an acceptable amount. I realize a rebuild will probably solve most of this problem but I'm on a real tight budget.

[Guy]

I've got my eye out for a 2nd hand turbo. What I wanna know is, what is an acceptable amount of shaft play and end float. Every 2nd hand one I've checked has had a noticeable amount of both. So what do they have NEW and what is an acceptable amount. I realize a rebuild will probably solve most of this problem but I'm on a real tight budget.

If you are on a really tight budget, find out how much a new set of bearings and seals are. I looked high and low in Aus and NZ for bearings and seals to suit a CT20 (2l-t turbo) or a rebuild .. best price on bearings was $350 or so from NZ, rebuild was $500+ .. bearings from some bloke in the states . less than $100 to my door ..

did the refit myslef (was not hard) used a scribe to mark the shaft and compressor wheel (very light scratch) so I could replace the compressor back in exactly the same position on the shaft.

about 20,000k's ago now I guess still in good order ..

If it is a non roller bearing core .. it will seem like there is a quite a bit of play in the shaft 0.1mm radial .. but should be no perceptable axial play (in\out)


This is shade tree mechanicing at it's best\worst .. may be a good idea to seek professional advice before proceeding

[bigcam]

end float should not be detectable by hand. if there is a very very small amount then you might get away with it for a while before you need to replace the thrust bearing.

side play there will be some as the shaft loats on oil when running just push the compressor to the side and turn all the way around to make sure the comp wheel doesnt touch the housing.

[PGS 4WD]

Depends on the turbo. A roller bearing has a small amount of end float and side play, it varies depending on the turbo size. A GT28 has less than a TO4ZR . Plain bearing or fully floating shouldnt have any end float and minimal side play, the impeller should have clearance to the housing, look for oil in the compressor housing and exhaust housing for possible seal failure, but uufortunatly it is't conclusive as the engine may have had high blow by and a closed breather giving a false impression. A plain bearing with significant end float or housing scoring can indicate a turbo worn beyond reconditioning requiring a ful CHRA (centre housing ratating assembly) that would almost equal the cost of a new turbo.

Joel

[RED60]

Thnks people...

[KiwiBacon]

How much you feel will also depend on how much oil the turbo has left in it.

A turbo that has been just pulled off a vehicle may have enough oil in the bearings to make it feel tight and smooth. The same turbo after sitting for a few weeks will probably have noticable movement and won't feel as smooth.

[Mark2]

I've just bought a second hand turbo which has no end movement but a fair bit of side to side maybe half a mm?? - to the point that it will touch the housing if you hold it firmly in one direction and try to turn it. Should I put it on the motor? I'm worried that if its touching the housing, it might put metal through my engine......... or is this normal for a non roller bearing turbo with no oil in it?

[Harb]

Depends on the turbo...... plain bearing turbo's rely on clearance to provide a coating of oil the turbine shaft "floats on"......
This is why its important to let plain bearing turbo's cool down when worked hard, so as to let the oil cool the bearing area down as much as it can before you shut down and let the turbine shaft sit back down as the oil pressure drops and the shaft slowly sits back down on the bearing....
In operation the bearing and the shaft should never touch one and other.......a film of pressurized oil should separate them...

[jaztaz]

The only proper way is to find manuf. specs & take a dial indicator on a magnetic base (put centre housing in vice with snails removed) & measure it for yourself. That's how I got taught at trade school.

[KiwiBacon]

I've just bought a second hand turbo which has no end movement but a fair bit of side to side maybe half a mm?? - to the point that it will touch the housing if you hold it firmly in one direction and try to turn it. Should I put it on the motor? I'm worried that if its touching the housing, it might put metal through my engine......... or is this normal for a non roller bearing turbo with no oil in it?

If it can touch the housing then it needs repaired.

Jaztaz is right that the only way to know if it's in spec is the dial gauge and manufacturers specs. But if it can touch the housing then it's definitely out of spec.

As for turbo cool down. Idling is bad for diesel engines, get an EGT gauge and safely shut the engine down when it gets below 200C. You'll find it hardly ever needs additional time to cool.
Idling your engine for two minutes on every shutdown does more harm than good.