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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
The 2 journal bearings on the shaft are designed to swim or float in a bath of constantly replenished oil. There is an oil clearance between the ID of the bearings and the shaft and OD of the bearings and the bearing housing and with no oil bath around them they won't be submerged and swimming in oil and there will be metal to metal contact.

edit: I forgot to mention the 2 shaft bearings rotate inside the bearing housing at about 1/2 shaft speed because of the inner and outer oil clearances while swimming in the oil flow around them. With the oil supply blocked off that can't happen and they would be damaged or worn.

This oil clearance is why there is always some lateral or sideways shaft play in a journal bearing turbo and there is no such thing as "zero clearance" in a journal bearing turbocharger because it's impossible... a ball bearing turbo could use that marketing term.
The thrust bearing the compressor wheel pushes against also needs a steady supply of oil.

If you ran the motor with no oil supply to the turbo the shaft bearings can't be floating in oil and were running without ample lubrication and they have been compromised.

Have a 360 degree thrust bearing installed when you have it rebuilt again. The UMW HFS turbo I have had a 270 degree thrust bearing in it and a worn out eroded bearing housing. I had it rebuilt by Durabilt Turbo the last time and there is no break in period with a Durbilt turbo. There's no reason for it when proper sized oil clearance origonal KKK parts are installed and they tell you that.

Last edited by JFairman; 08-04-2011 at 11:28 AM..
Old 08-04-2011, 10:03 AM
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