Turbo Bearing Failure Symptoms

What This Means

Your turbo spins on a set of bearings that float on a thin film of pressurized engine oil. Most turbos use journal bearings (also called sleeve or floating bearings) to handle the shaft spinning at speeds north of 100,000 RPM, plus a thrust bearing that controls how far the shaft can move front to back. When those bearings start to wear, that oil film breaks down and the shaft loses its precise centering. That’s when you get the compressor or turbine wheel rubbing the housing, excess shaft play, and oil getting pushed past the seals.

Bearing failure is usually a slow-then-fast process. The bearings wear gradually as clearances open up, and then once the shaft starts contacting metal the whole thing comes apart quickly. Catching it at the play and smoking stage is the difference between a clean rebuild and a turbo that grenades and sends wheel fragments into your engine or downpipe.

Common Causes

• Oil starvation from a clogged feed line, restricted banjo filter, or low oil pressure, which can wipe out the journal bearings in seconds
• Dirty or contaminated oil carrying abrasive particles that score the bearing surfaces and shaft journals over time
• Extended oil change intervals letting carbon and sludge build up and starve the bearings of clean flow
• Hot shutdowns where you kill the engine right after hard pulling, coking the oil inside the center housing and choking the feed passages
• Sustained high-boost operation beyond the turbo’s design, which loads the thrust bearing harder than it can handle and accelerates wear
• Aggressive throttle cycling and constant on-off boost that hammers the thrust bearing back and forth
• A failing or worn-out oil pump or the wrong oil viscosity, which thins the protective film the bearings depend on

How to Diagnose It

• Pull the intake and exhaust ducting, grab the shaft by the wheel nut or wheel, and check for play. Side-to-side wiggle that lets the wheel touch the housing means the journal bearings are gone. A little radial play is normal, but contact is not.
• Check axial play by pulling and pushing the shaft front to back. More than a few thousandths of in-and-out movement points to a worn thrust bearing.
• Look inside the compressor housing and on the back of the compressor wheel for oil film. Oil there most often comes from a clogged air filter, a restricted oil drain or too much crankcase pressure; worn bearings are one possible cause, so rule out the others first.
• Inspect the compressor and turbine wheel blade tips for rub marks or bent edges where they’ve kissed the housing.
• Watch your tailpipe on startup and under load. Blue smoke at idle or when coasting means oil is getting into the intake or exhaust: that can be the turbo’s seals, but a restricted drain, crankcase pressure or valve stem seals cause the same thing.
• Cut open the oil filter or check the drain for metal flake and bearing material, and verify you actually have oil pressure at the turbo feed before you blame the turbo itself.

Can You Replace Turbo Bearings?

Yes. Turbo bearings are wear parts, and replacing them is the core of every rebuild: new journal bearings, thrust bearing, thrust collar and seals go in, and the turbo goes back to factory clearances.

What does not work is pressing new bearings into the housing and bolting the turbo back on. Three things have to happen around the bearings:

• Measure first. The shaft journals and the bearing bores in the center housing have to be within specification. New bearings on a scored shaft or in a worn bore fail again quickly.
• Find the cause. Bearings rarely wear out by themselves. Oil starvation, dirty oil or a restricted drain will take out the new set the same way.
• Balance the rotating assembly. The shaft and wheels turn at more than 100,000 RPM. After it is reassembled, the assembly has to be balanced at speed, or the new bearings are hammered from the first start.

That is why a bearing kit by itself is a job for a shop with a balancer, and why turbocharger bearing replacement in practice means a rebuild. Ball-bearing turbos are a separate case: the bearing is a one-piece cartridge that is replaced as a unit. Prices for a rebuild, which includes the bearings, are on our turbo rebuild price list, and we confirm the price after inspecting your turbo.

Rebuild or Replace?

If you catch the bearings while there’s still shaft play but the wheels haven’t contacted the housings, a rebuild is almost always the right call. We replace the journal bearings, thrust bearing, thrust collar, seals, and the retaining hardware, then balance the rotating assembly. As long as the shaft journals and the bearing bores in the center housing are still within spec, the core is perfectly good and a rebuild brings it back to factory clearances.

Full replacement comes into play when the failure went far enough to damage the wheels or housings. If the compressor wheel ate itself, the turbine wheel cracked blades, or the shaft journals are scored deep enough that new bearings won’t seal, you’re past a basic rebuild. Same goes if the center housing bore is worn oversize. At that point the cost of replacing the damaged hard parts can approach a new unit, and we’ll tell you straight whether your core is worth saving or not.

Frequently Asked Questions

Turbos We Commonly See With This Issue

• BorgWarner S472 Turbo Rebuild Service
• BorgWarner S475 Turbo Rebuild Service