Spun Bearing???

Hey guys, recently my car has overhaeted a few times but not for too long. I drove it maybe a quarter mile with the needle in the red(obviously that was too long) and now I have a horrible engine knock, and sometimes the car dies randomly after or wont want to start up. I only hear the noise at anything about above 2k and slightly at idle.. is a spun bearing possible? or could it be something worse? either way i guess its time for a rebuild or a new car, but i would still like to know whats going on under the hood.. Any suggestions??? the engine has 240k on it as well

If you blew the head gasket while it overheated and coolant got in the oil there is a good chance you spun a bearing, also when things get hot they expand and the bearing could have definitely hit the crank and all it needs to do is touch the crank for a micro second and it will spin. Look up rod knock sounds and compare. I would check the oil and if it doesn't look right there is coolant in it meaning the head gasket when and coolant has no anti friction properties so when it went through the system it could have went to a rod and the rod hit the crank and the bearing spun.

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Originally Posted by Galanttuner10

If you blew the head gasket while it overheated and coolant got in the oil there is a good chance you spun a bearing, also when things get hot they expand and the bearing could have definitely hit the crank and all it needs to do is touch the crank for a micro second and it will spin. Look up rod knock sounds and compare. I would check the oil and if it doesn't look right there is coolant in it meaning the head gasket when and coolant has no anti friction properties so when it went through the system it could have went to a rod and the rod hit the crank and the bearing spun.

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You do know that the bearings are always in contact with the crank right? Two bearing surfaces plus oil means wear is kept to a min. When you add water to the equation (coolant) which has no lubrication properties what so ever you now have friction. Friction causes heat, bearing expands, bearing binds on other bearing surface and gets worn down. The clearance then becomes to large and the rod has slop on the crank thus causing it to knock.

It's 100% plausible that you did do some damage to the lower end. Should pull the oil pan off and have a look. Worst case you are looking at some new bearings and a crank re polishing, or a new crank and some bearings depending on how bad it is.

The bearings are never in contact with the shaft main or rod. There is .001 clearance on a side and the oil keeps that clearance. As soon as a bearing touches the crank it spins. That is why if you look at any good set of used bearing the only very slight visible wear is on the bottom half from gravity on initial start up before oil gets there. Hence why most engine wear is on start up.

ASE certified in engine repair :)

Also when a bearing spins it doesn't wear down, it actually spins into the other bearing half and then there is no bearing on half the rod. The knocking does come from extra clearance but not how you described.

So here are causes to the OP issue, because you overheated everything got hot and expanded and the bearing hit the crank and spun which if your coolant level is good is probably the cause. If the HG blew as well it was the same thing plus coolant in the oil which probably accelerated the issue. Just go check your coolant level first to see what the probable cause was.

funny story about the coolant though. there was hardly anythign in there at all. I stripped out the threads in the thermostat replacing the intake manifold, and i finally out some helicol in it a week ago.. i mean it wouldnt hold any fluid at all. as of now, im looking to rebuild the engine. im gettin a 1500 check next month and need something to blow it on lol

i also wanna thank you guys for the quick replies here.

Bearing clearances compensate for expansion due to heat as well as oil pressure. Ever pulled an old engine apart? There is plenty of contact between the crank and the bearings over time. The higher quality the bearings the harder contact has to be to make them spin. If this weren't the case then an old banana peel would work as a bearing and it sure as hell doesn't.

The tighter your clearances the higher oil pressure you'll run and ultimately less protection you'll get. There is a sweet spot, implemented by manufacturer design that dictates the best clearance to get the most safety to the bearings.

Higher quality bearings are no less prone to spinning than low quality, the crush is what holds them into place. And have you ever looked at a set of old bearing? Where is the wear? Bottom of the mains and the top of the rods. Main wear is from start up and the wear on the rods is from the spark plug firing and the resulting force pushing it back down the bore. They never actually touch for more than a split second and if they do they spin period. The difference between aluminum and tri metal are things like embed ability and coatings etc. stock bearings are aluminum for almost every car and last 200k plus in most occasions. Bearings fail for reasons detonation, lack of oil, too little clearance, coolant in the oil as coolant has no anti friction qualities and leads to contact between the bearings and the shaft. Places where clearances are more for expansion are pistons and that is why they are cam ground.

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Originally Posted by Galanttuner10

Higher quality bearings are no less prone to spinning than low quality, the crush is what holds them into place. And have you ever looked at a set of old bearing? Where is the wear? Bottom of the mains and the top of the rods. Main wear is from start up and the wear on the rods is from the spark plug firing and the resulting force pushing it back down the bore. They never actually touch for more than a split second and if they do they spin period. The difference between aluminum and tri metal are things like embed ability and coatings etc. stock bearings are aluminum for almost every car and last 200k plus in most occasions. Bearings fail for reasons detonation, lack of oil, too little clearance, coolant in the oil as coolant has no anti friction qualities and leads to contact between the bearings and the shaft. Places where clearances are more for expansion are pistons and that is why they are cam ground.

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You have no clue what you are talking about.... Would just stop, ASE certified or not you have no understanding of engineering and what goes on inside that engine clearly.

when I pulled my 4g 63 apart I noticed exactly how he's describing the wear top of the rods bottom of the main and I was wondering aboutit but I was replacing the bearings anyway and they didn't look bad so I didn't give it anymore thought . Learn something everyday

Have you ever heard the term "curing" the bearings? When you break in an engine the bearings temper up to the point that they can be harder than the main girdle and rods. The structural rigidity of the bearings holds them in place, in order to spin they have to be hit very hard. This isn't saying much in a rotating assembly but the idea of zero contact is retarded. What do you think wears bearings out over time? Fucking contact. Bearings fail when there is TOO MUCH Clearance and it becomes impossible to maintain an oil membrane.

And yes, I've pulled more lower ends apart and put more of them back together than you ever will.

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Originally Posted by Silvertune

Have you ever heard the term "curing" the bearings? When you break in an engine the bearings temper up to the point that they can be harder than the main girdle and rods. The structural rigidity of the bearings holds them in place, in order to spin they have to be hit very hard. This isn't saying much in a rotating assembly but the idea of zero contact is retarded. What do you think wears bearings out over time? Fucking contact. Bearings fail when there is TOO MUCH Clearance and it becomes impossible to maintain an oil membrane.

And yes, I've pulled more lower ends apart and put more of them back together than you ever will.

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i said that the bearings touch for a split second in certain cases but you need to understand the engineering right? it is engineered to have 1 thousandths clearance on a side and the rod bearings are actually narrower toward the parting line so they can survive a good amount of detonation. if they hit too hard or for too long they spin period as i said before. bearings don't only fail for too much clearance, thrust bearings get whipped from improper clutch adjustment or a torque converter overheating and pushing into the motor. bearings also fail from to little clearance as that spins the bearing. you guys just have a complex you have to get across and i get that and some of what you say is wrong but we have mitch who say the bearings are always touching which is so wrong i laughed but i know nothing. in a perfect world the bearings have a thousandths clearance on a side, things hinder this like the crank sitting for a while and gravity and detonation really kills bearing but for sake of informing people you have to talk about in a perfect world to get the point across. i can use words and language that will make him have more of a headache then answers but i wont. i explain a simple concept. why don't you guys go pass the test or at least look up the practice test as everything is about being in a perfect world no exceptions bullshit but yes there are always exceptions which is beyond the scope of this thread. if you guys have issues, actually think about what you are saying and its not about how many engines you have taken apart seen or built its how long they all last and how much pride you took in putting them together. i for one take pride in what i know and do and don't have to put people down because i feel i need to. shit i let mitchs comment go until he said i know nothing. you guys talk a lot for no reason and only clutter up threads.

Getting umm lol

started to rebuild the engine a few weeks ago. if i can get the crank out sometime soon then i shall be sending it off along with the head to get re done as well. at this point id really love to do the evo8 swap, but i doubt i have the bread for it. thanks for the input and ill try to keep you guys posted

It's gonna be cheaper to buy a junk yard motor and have it replaced. Machinework is pricy.