what does it mean when you spin a bearing?

[Blitzed95Eclips]

Im trying to be hip with the lingo. What does it mean when you spin a bearing. I constantly hear of people doing this and it destroying their motor. I figure it has to do with the same bearings i had to replace because of crankwalk.

 

[Defiant]

Nearly, but not usually. A spun bearing refers to a plain bearing - two half-circle, steel-backed, copper/tin/antimony/etc. bearings as used on connecting rod big ends and in the crank main bearings. When they have a lubrication failure -either a lack of oil supply, or an overheating of the oil to the point it's the same effect, or are in some way mechanically abused to the point that they no longe fit their saddles- they can seize on the surface of the shaft they're supposed to bear (hence, "bearing") and stick or weld themselves to the shaft so tightly that they try to whirl around _on_ the shaft- and thereby "spin".
It's very rare that they'll finish a lap, most often they'll get just far enough that the tang that's supposed to hold them in place wedges again, then if it's a connecting rod, the rod will often snap, and if it's a crank bearing, it'll seize the motor up. It's also common that only one half of the bearing will seize, and you'll find it stacked on the other half of the bearing still in the saddle.
It's very nasty, and often results in both a block and crank that are no longer useable.
The "crankwalk" bearing has another pair of faces on it, front and rear, besides the one the crankshaft rotates on: it's the thrust face, and is a part of the crank bearing that wraps up along the cheeks of the middle crank bearing saddle, and has surfaces which the cheeks of that crank journal bear against during axial crank load, such as cornering and when using a clutch. These extra faces make it a little less likely to spin, unless there's an oiling failure, and even then it probably won't be the first one to go.

 

[jb talons]

I just had this happen with my motor. I actually spun two of the rod bearings with only 67K miles on the car.

I wanted to try to find out how common this is in the 4g63 engines. I hear a lot about crankwalk, but not much about spun bearings.

Are there any resources or websites to check this out?

 

[RallyxDave]

Check out my website and you can see what a spun bearing looks like...I had it happen to me early last year.

http://www.4x4racecar.net/rebuild.htm

 

[talonted_one]

another spun bearing victim here

 

[jb talons]

RallyxDave,
I looked at your site. It looks like you have a lot of fun with your talon. It also looks like your engine sees more abuse than the normal daily driver.

talonted_one,
What kind of mileage was on you engine when the bearing went? What were the repairs that you needed?

 

[dcskater82]

yeah ive got two friends who have spun their bearings, one a 95 tsi, and the other a 95 gsx, the tsi guy spun his twice before going 6 bolt, gsx recently spun a bearing and will be going 6 bolt. ive just rebuilt my motor due to crankwalk, but i dont know what to be more fearful of when i get it back, spinning a bearing, or walking again....hpoefully neither, at least until i have the funds for a 6 bolt...oh well.

 

[red clipse]

Spun bearing victim

It wasn't that bad. Just snapped the rod and put one end through the side of the blockr resulting in a 3 in. wid hole. The big end of the rod that connects to the crank was actually ripped off the crank. One of the bolts that holds the cap down was ripped out and the other bolt was somehow twisted and mangled along with the rest of the cap. I fell out when I dropped the oil pan. I love my car.

 

[Boost Era]

Im currently rebuilding after a spun main bearing... Im having a b!tch of a time finding the correct bearings. The machine shop that Im working with can only get me bearings with a full soild bearing with a flange on it and cant seem to find and with the proper washer bearings... I ready to put everything back together but I still waiting on the right damn bearing to be found.

 

[larryd]

I spun one of the rod bearings on my 7 bolt many moons ago, it was due to a failing oil pump.

 

[jb talons]

I'm still curious as to what kind of milage people are having spun bearing problem. I had mine go bad at 67K. I can't figure out any thing that could have lead up to this.

 

[larryd]

Mine went at about 56k if I recall, as I said though mine was due to a failing oil pump.

 

[Kingdom]

Spun Bearing here, 7-bolt.

Most probable cause, failing oil pump - abuse. 6-bolt swap next.

 

[jb talons]

I'm wondering if a failing oil pump is the common factor. Maybe that also shows up with the ticking lifter sound. Of course I never, ever abuse my motor.

Larry, what's the new picture in your sig?

 

[larryd]

Picture of my old Celica.

 

[Davidle]

His sig pic IS his Eclipse, the bodys just converted into a celica. . J/K.

 

[larryd]

Wouldnt that be interesting.

 

[Defiant]

I'm surprised no one's asked about the Eclipse --> Celica swapout yet.

The VFAQ must be much better than the FWD --> AWD one.

 

[RipperXX]

ack! my car has 175,000 miles on it and the bottom end has never been rebuilt... crap! uhh hmm... think i will do that as soon as i can aford it now..

 

[Ryan95tsiAWD]

invictus rocks the spun bearing!

i have 180k now on my 95
my first engine rebuild was at 168k ....i gave it hell the whole time...thought i was unlucky...then i looked around and saw how long my car actually lasted!

...now for the rest of my problems

 

[boostle]

My 98 gst ate up the rod bearings exactly at 99,995 miles. I'd say the root cause was too much boost on cheasy 91 octane.

 

[mrmadmax]

Originally posted by Defiant

...
When they have a lubrication failure -either a lack of oil supply, or an overheating of the oil to the point it's the same effect, or are in some way mechanically abused to the point that they no longe fit their saddles-
...
most often they'll get just far enough that the tang that's supposed to hold them in place wedges again, then if it's a connecting rod, the rod will often snap, and if it's a crank bearing, it'll seize the motor up.
...

One more major cause of bearing failure that is not mentioned above is from incorrect machine work. The "tang" on one end of a plain bearing shell is not intended to hold the bearing in place, but rather to correctly position the bearing half during assembly. Plain bearings are held in place because they are actually larger than the bore that they are installed in. You can verify this by placing a bearing half into a connecting rod or main cap and observing that part of the bearing half sticks out past the parting surface. This is refered to as "bearing crush", and should measure around a few thousandths of an inch.

If a machinist bores a mainline or connecting rod bore too large, then the bearings have no/too little crush, and therefore no pressure between the bearing half and the bore. It is this pressure that keeps the bearing from "spinning". An oversized con rod / main bore will sheer off the "tang" on the bearing in a very short timeframe.

Further, all plain bearings generate heat due to the shearing action of the lubricating oil, and this heat is released in part into the housing that is bored to hold the bearing. By having too little contact pressure between the bearing and it's housing, the bearing can't get rid of the heat, so it fails.

Too much bearing crush has adverse effects as well.