Main Bearing Failure - Thrust Surface
 

Though we're not sure about the failure, attached is the rear main bearing form my 15 Hour engine. It appears that the thrust surface is most warn indicating a crankshaft thrust problem. What are the typical causes of this type of failure? I want to check everything to avoid this in the future.

Some info on the engine:

Reworked 7.4L with a Procharger, Roller cam, roller lifters, roller rockers, Eagle forged crank, JE Pistons, Dart Heads. Stock
Bravo 1 drive.

Appeared to be a very good rebuild until the bearing went out.

Any ideas?

Thank You,

Kirk

I Had had a problem on a truck engine eating up thrust bearings,it was caused by the stock torque converter ballooning under load and causing thust bearing failure that led to excessive crank end play.I have heard that some Eagle Cranks had a Radius that was too large causing the rod bearings to bind.Maybe your mains have a similar situation Check your crank with a new bearing half and see if there is clearance in the radius.There are some sharp Guys on this board and I am sure someone has seen this before. PS what prop are you running at what rpm/mph?

Good Luck
Rob

Thanks
 

We're checking the coupler and the drive shaft length etc... Something caused this and if we eliminate the external parts, it has to be something internally.

I'm running a 29P Mirage Plus, haven't had it opened up to WOT. My speedo only goes to 80 and it was buried aroung 4,500 RPM.

I have since bought a 100 MPH speedo. When I get the engine back in I'll post my numbers to see if I'm doing everything correctly, ie prop pitch, gear ratio, etc...

Thanks for your post. I'm hoping Mr. Dennis Moore will chime in here!!!! I didn't see pictures like that in his book though!!!

What was the end play in the thrust when the motor was assembled? It is hard to tell from the picture, but are you sure the failure is end play or thrust related and not just an oiling problem with the main bearing?

Is the copper of the bearing loose???
It doesnt look like end play failure- it looks more like improper clearance or lack of proper oil preasure to the bearing. That bearing had to get real hot to do that.

I tend to agree along with Tinkerboaters thoughts, adding possible partial blockage of oil passage to this rear main bearing.
Looking at the photo, it appears there is still a small line of bearing surface remaining on the left, bottom side, by the parting line of the bearing shell. If this is true, the last bearing journal surface could be ground on a taper. Its also possible the bearing cap was installed with foriegn material under that corner of bearing cap.
Is crankshaft straight? Was bearing cap tight (torqued) when engine was disassembled ?
Why is there so much contamination on the bearing cap mating surfaces ?
If bearing cap was not properly torqued during assembly, imagine how that cap will walk around with the oil pump mounted on it.
Do you have the "as built"bearing clearances ?

Hope this helps, David.

Is the seal the right one? I know yellow is for right hand,all merc drives are left hand engines.Was their oil in the bilge?

Did you check the engine alignment ? I had the same problem

and it was caused by the motor droping on one side and

throwing the motor out of alignment

when your motor is out of alignment and you trim the drive it

puts pressure on the coupler-flywheel-crank

Thanks for the info
 

We are checking the alignment of the bearing bore this week. We will also check out the crank.

Six Leg, you are correct, the engine builder did install the wrong seal. He claims that he has been installing the yellow seal in hundreds of engines. He didn't know that they were for reverse rotation. (scary huh?) He also claims that that couldn't be the cause of the failure. I agree it may not have cause the failure, however with the flutes in the seal facing the wrong way, the seal acted like a pump if the inner seal was torn.

I don't know that we'll ever figure this out, but I'd like to see everyones input so that I can check everything. I don't want to do this again in another 15 hours!!!!

The thrust side that is worn is the rear side. This shows that the crank is being pushed/pulled forward. The oil comes to the bearing at the center of the journal. If you had an oil problem it would be with the entire bearing, I think.

On a passenger/truck engine this type of problem is usually caused by the torque convertor not being installed correctly when assembled. The convertor isn't seated completly on the front of the transmission and pushes against the flex plate and wears the thrust out.

Since you don't have a torque convertor, but you do have a flywheel and drive plate, I would look at that area. Something is pushing the crank forward when it is bolted up.

I don't see where the wrong seal will cause it. It will cause a leak, but that's about all. There is no suction there it is more of a scraping to push the oil back away from the seal.

I have seen, now only once where the timing chain was installed wrong, 5.7 Chevy, and when the harmonic balancer was installed it pulled the crank forward. Doing the same damage to the main thrust also. But, that was only once and is alittle out there.

Did the builder check the end play when the engine was assembled??? Or did he just assume he had it.

Good luck, just my $.02

I'm probably way off on this but when we re-rigged the race boat we learned that you shouldn't mount the engine so that the drive shaft was right in line with it. In other words you need a little bit of an angle in the connection between the two to prevent things getting hot, anyway just a hunch.

Like GearHead said be sure and check end play that is a must.

This may not be the cause of the failure but check every radii on the crank, we had three Eagle cranks that had to be reworked because of to large of a radius

Looks like a bearing clearance problem, were they checked during assembly. Was the block align bored to accept the new crank? If you had a clearance problem with the bearings was it caused by a crank that was not ground true on that journal? What was the initial oil pressure? and after the failure what was it? Hope my .02 helps. good luck

I have the same problem, a burned up thrust bearing. But, with all of the excess heat, I cranked my block. No other bearing damage, just the thrust. Mine had a eagle crank also. So it didn't starve for oil. I was told that some excessive external force was the cause. And to check the rigging.
I'm thinking of getting the inside splines cut down about 1/2" on the couple, to give me a little more clearance.
Has anybody tried this?

External Force?
 

Though that would be a cause of the thrust failure, this engine was in the boat for 2 years before the rebuild. No changes were made to the drive, coupler or flywheel.

I'm leaning toward a bad assembly or bad crank journal. It appears that that is what other seem to think.

ANy other recommendations or items to check??

I'm hoping mines in the assembly. I've had it for a year, with no problems with the motor. Except, blowing the drives. So after two drives, I went with a Imco extreme. A month later, thats when it happen.
Everything is within specs. The input shaft, thickness on transom, and the line up.
So right now, I have a cranked block and parts that are junk.
And I'm still unsure what caused it. Keep me informed on yours. It might help me out later. Thanks

My worst damage was with inside mains. (2,3). Lots of garbage in everything else. Had an overheat problem a few tach hrs. prior to the drop in O.P. but never thought that it had effected the lower end. Turns out, the excess heat made the main journals something short of perfectly round. Would recommend having alignment and roundness thourghly checked prior to reassembly. LOL --- Jer

Well, I ain't Dennis Moore, but I ain't chopped liver either... lol By the looks of your photo, I have a pretty good idea as to why the bearing failed (in your case) and included some other options to check as well. The rear thrust bearing of a Chevrolet motor is not able to support the load the other bearings do, and oiling is achieved in a totally different manner than what you may think. Although thrust bearings run on a thin film of oil, just like radial journal (connecting rod and main) bearings, they cannot support nearly as much load. While radial bearings can carry loads measured in thousands of pounds per square inch of projected bearing area, thrust bearings can only support loads of a few hundred pounds per square inch. Radial journal bearings develop their higher load capacity from the way the curved surfaces of the bearing and journal meet to form a wedge. Shaft rotation pulls oil into this wedge shaped area of the clearance space to create an oil film which actually supports the shaft. Thrust bearings typically consist of two flat mating surfaces with no natural wedge shape in the clearance space to promote the formation of an oil film to support the load. A rear main seal directs oil towards the rear bearing to aid in lubrication, and to keep the pressurized oil from being pushed out past the crankshaft and oil pan... plain and simple (see below). A boat motor operates under a severe load from forces being exerted on the prop, up through the outdrive. There is undoubtable eveidence of extreme overheating of the bearing load surface and I have no doubt the incorrect rear main played a major role in this failure. I made the things I feel are most probable to your problem in bold print, and have seen failures as yours from all of them at one time or another, not saying any one single item listed is positively what created your problem. Trouble is, after the damage is done, then theory and careful process of elimination is all you have to figure it out. If none of the other bearings were damaged, then I have to say the wrong rear main seal played a major role in this failure, but some of the other things listed could be happening as well. I hope something here turns on the light and helps you determine the cause, and solve it.

Here is an explanation of bearing oiling from Clevite Bearings...
Although thrust bearings run on a thin film of oil, just like radial journal (connecting rod and Main) bearings, they cannot support nearly as much load. While radial bearings can carry loads measured in thousands of pounds per square inch of projected bearing area, thrust bearings can only support loads of a few hundred psi. Radial journal bearings develop their higher load capacity from the way the curved surfaces of the bearing and journal meet to form a wedge. Shaft rotation pulls oil into this wedge shaped area of the clearance space to create an oil film, which actually supports the shaft. Thrust bearings typically consist of two flat mating surfaces with no natural wedge shape in the clearance space to promote the formation of an oil film to support the load. Conventional thrust bearings are made by incorporating flanges at the ends of a radial journal bearing. This provides ease in assembly and this design has been used successfully for many years. Either tear-drop or through grooves on the flange faces and wedge shaped ramps at each parting line allow oil to enter between the shaft and bearing surfaces. However, the vast majority of the bearing surfaces and all of the shaft surface is flat making it much harder to create and maintain an oil film. If you have ever taken two gauge blocks and wiped them perfectly clean and pressed them together with a twisting action you know that they will stick together. This is very much like what happens as a thrust load applied to the end of a crankshaft squeezes the oil out from between the shaft and bearing surfaces. If the load is too great, the oil film collapses
and the surfaces want to stick together, resulting in a wiping failure.

Causes of main bearing failure:
Aside from the obvious causes, such as dirt contamination and misassembly, there are only three common factors which generally cause thrust bearing failures.
They are:

Poor crankshaft surface finish

Misalignment

Overloading

Main bearing Loading:

A number of factors may contribute to wear and overloading of a thrust bearing, such as:

1. Poor crankshaft surface finish.

2. Poor crankshaft surface geometry.

3. External overloading due to.

a) n/a Excessive Torque converter pressure.

b) n/a Improper throw out bearing adjustment.

c) n/a Riding the clutch pedal.

d) Excessive rearward crankshaft load pressure due to a malfunctioning front mounted accessory drive.

Engine related problems:
Is there evidence of distress anywhere else in the engine that would indicate a lubrication problem or foreign particle contamination?

Were the correct bearing shells installed, and were they installed correctly?

If the thrust bearing is in an end position, was the adjacent oil seal correctly installed? An incorrectly installed seal can cause sufficient heat to disrupt bearing lubrication.

Examine the front thrust face on the crankshaft for surface finish and geometry. This may give an indication of the original quality of the failed face.

Believe it or not this is a big problem, and overlooked 99.9% of the time...
Other External Problems. Aside from the items already mentioned, there is another external problem that should be considered. Inadequate electrical grounds have been known to exacerbate thrust surface wear. Excessive current in the vehicle drive train can damage the thrust surface. It affects the thrust bearing as though the thrust surface on the crankshaft is not finished properly finished (too rough). Excessive voltage in
the drive train can be checked very easily. With the negative lead of a DVOM connected to the negative post of the vehicle battery and the positive lead on the transmission, there should be no more than .01 volts registering on the meter while the starter is turning over the engine. For an accurate test, the starter must
operate for a minimum of four seconds without the engine starting. It is suggested to disable the ignition system before attempting this test. If the voltage reading observed is found to be excessive, add and/or replace negative ground straps from the engine to the vehicle frame and transmission to frame until the observed voltage is .01 volts or less. Note: Some systems may show a reading of .03volts momentarily but yet not exhibit a problem. For added assurance, it is a good idea to enhance the drive train grounding with larger battery cables or additional ground straps.

An easy mod to help lubricate stressed rear thrust bearings (images below)
A simple modification to the upper thrust bearing may be beneficial in some engines. Install the upper thrust bearing in the block to determine which thrust face is toward the rear of the engine. Using a small, fine tooth, flat file, increase the amount of chamfer to approximately .040" (1 mm) on the inside diameter edge of the bearing parting line. Carefully file at the centrally located oil groove and stroke the file at an angle toward the rear thrust face only, as shown in the illustration below. It is very important not to contact the bearing surface with the end of the file. The resulting enlarged ID chamfer will allow pressurized engine oil from the pre-existing groove to reach the loaded thrust face. This additional source of oiling will reach the loaded thrust face without passing through the bearing clearance first (direct oiling). Since there may be a load against the rear thrust face, oil flow should be restricted by that load and there should not be a
noticeable loss of oil pressure. This modification is not a guaranteed "cure-all". However, the modification should help if all other conditions, such as surface finish, alignment, cleanliness and loading are within required limits.

http://home.attbi.com/~fordhater/bearing1.jpg

http://home.attbi.com/~fordhater/brgmod.JPG

The procedure below will align the bearing thrust faces with the crankshaft to maximize the amount of bearing area in contact for load carrying.

When assembling thrust bearings:

1.Tighten main cap bolts to approximately 10 to 15 ft.lb. to seat bearings, then loosen.

2.Tap main cap toward rear of engine with a soft faced hammer.

3.Tighten main cap bolts, finger tight.

4.Using a bar, force the crankshaft as far forward in the block as possible to align the bearing rear thrust faces.

5.While holding shaft in forward position, tighten main cap bolts to 10 to 15 ft.lbs.

6.Complete tightening main cap bolts to specifications in 2 or 3 equal steps.

Lastly, if you have a crank that is not true, you will have irregular wear on several of the other bearing halfs, some upper, some lower, some on the edges etc. Also, anything creating harmonics or vibration, like assy belts being loose, belt mis-alignment, or an out of ballance flywheel is possible. I presume the flywheel was ballanced with the rotating assembly and bob weights? Good luck my friend, my heart goes out to you... I hate this $hit.... ~smile~

Where does this guy dig all this stuff up? As usual, another great job from Find-Me.:) :)

Man, learned something new again today. Thanks

What is the difference in the rear main seals? I though you wanted it installed facing the rear main. Or are you saying there are grooves on the seal that rides on the crank that throws the oil back in, instead of pulling it out (like a screw)

I think they are talking about difference in rotation of motor. Clockwise or counter clockwise. CW or CCW use a different seal. There are screw type grooves as you say to channel or pull the oil back in to the motor. As to how much this had to do with this bearing failure I guess is a matter of opinion. FindMe has some great information. I have seen bearings set up like he notes before. I had a rear main tight until assembled exacly like FindMe noted.

I wish I new exactly what all the clearances were at assembly including thrust. Crank runout is it straight. Eagles have to run extra radiused clearance on the bearings but if it ran 15hrs hard to say. I really would like to know rear main clearance. Was it .0035 or less? With as much heat as I see I would deffinently line bore the block. Just my .02. :D

Thank You Find - Me
 

Thank you very much for the most in depth explaination I could ask for. I believe that the highlights your reply are the most logical contributions to this type of failure. The engine is in the shop having the bearing bore checked. We will try to measure the main journal diameter to see if there was a clearance problem. I think a good line bore and matched crank and bearings will solve the problem, oh and the correect seal!!!

The engine builder says he has installed this seal in numerous engines, he didn't realize it was a reverse rotation seal!!!!

Its a shame that there a companies out there taking peoples money and claiming to be professionals, yet they do not know the basics such as this. I shouldn't have to tell the builder that the seal is incorrect.

So far he says he's willing to work with me to repair it, he just seems to have lost my phone number. I left several messages and emailed them my home, work and cell numbers...to date, no reply.

Thanks again Find-Me

Kirk

Well, all I can tell ya is the rear main seal has angled grooves in it to direct oil in a certain direction under load, and since the rear brg thrust style crankshaft is well known for being weak and poorly lubricated, I think directing oil away from it in any capacity is suiside. Now, put the hammer down, and think about the splash or "directing" of the oil @ 4800 RPM with the bow of the boat in the air (rear main seal at lowest point) with oil being forced AWAY from the thrust main, instead of towards it and it ain't too hard to understand (in theory of course)... The rear cam bearing placement or rotation plays a role in oiling the last main as well (or how fast it can bleed off to the least restrictive point of escape). Im surprised you guys have never heard of "Pro-Blend"... it was designed by Funny Car driver Brad Anderson, and actually draws oil TO a hot spot, whereas usually it will move away. I watched him do a full 1/4 mile pass with a treated alcohol funny car motor without a oil pump belt, and it had NO oil related failures at the end of the run (brgs hammered from no cusion of oil, but nothing looking like your rear main brg, obviously cooked from extreme heat. PLUS, oil not only lubricated engine parts, but it cools them too.... Wala the oil cooler was invented and loved by all. Here is a half assed pic of oil moving away from a hot spot, and the resulting added failure area... I don't know how much the rear main seal plays into this, but if Clevite and all the other major brg manufacturers supply the information I posted, I'm inclined to believe it, plus the fact that the worst & most burnt part of your bearing is facing the rear main seal ain't it? I hope you get this one 1st try, good luck! I didn't invent the wheel.... Im just Rollin with it!

One last question?? Is that an adapter to make a 1 piece rear main motor, a 2 piece rear main, or am I seein She-it ? Almost looks like the cap was loose... or a very nasty mating surface? Hmmmmmmmmmmmmm???

http://home.attbi.com/~ls454ss/brghotspot.jpg

http://www.offshoreonly.com/forums/a...?postid=429572

Main Seal Adapter
 

I believe the main seal adapter is furnished with the crank kit from Eagle. The engine is an original 1998 7.4L, the crank is for a 502 I believe. I plan on installing a real crank like Lunati or Scat this time. Iv've heard nothing but horror stories about Eagle and the lack of tolerances and finish.

Kirk

Not to be a wise ass...., but don't ya think a "real rear main seal" would be appropriate? My bet is, you could put "real cranks" in all day with the seal backwards and have lots of trophies, instead of just one...lol
Sorry, but I just had to... my badd.. ~grin~

I read somewhere today, that Eagle cranks are good stuff if installed properly, with chamfering blueprinted (matching components). And the tolerances and finish issues if so, would get the builders ass kicked if they failed to properly check and record the clearances during assembly, or tell you to take the slug someplace to get polished or shove it cause they ain't puttin it in like that...... I have tested a few attitudes with that one, but every last one avoided major failures and the joy of having the little woman chewing around the seat of your pants, and letting your ass fall out.... (humor) but not funny.........

Well Warlock, you really ARE a wise-ass but I also really like your knowledge AND style. --- Jer

My engine builder has used Eagle cranks for years with very little problems since his first problem with a Ford 347 stroker. Had a MAJOR oil leak from the rear main. Come to find out the seal surface was out of round:mad: . Also has found some finishes not as nice as he would like so he polished them. But like Findme says , you have to check Eagles very carefully end to end.

Any recourse?
 

What is the opinion of the board on this situation?

I purchased the boat with the motor in late August. The motor was represented as a fresh professional rebuild with approximately 10 hours. Within a week of owning the boat I noticed oil in the bilge. Upon noticing the location of the oil source, a mechanic recommended pulling the engine for inspection. We unfortunately found the bad rear main bearing.

The original builder does not believe that the reverse rotation seal could have caused the failure. I now am faced with buying a new block and all the associated machining, parts and assembly associated. This will cost several thousand dollars. What recourse if any do I have? I have documentation on the whole situation with dates and of course dated work tickets from the mechanic.

I know I'm gonna get it for this but...

In none of your posts do you mention that this motor was severly over-temped and run hot for a period of time before shut-down when you first got it.

Not saying that caused your problems, but please correct me if this is not an accurate....

BTW - I know how it feels, I've cooked motors before. There's lot to be said for stock motors. I'm keeping mine that way for the time being...

I have to agree Checkmate454mag!!!!!
The rear main seal does NOTHING to lubricate the rear main bearing. You could leave it out and, as long as you had oil left, the only problem would be the mess. Many engines use a different bearing for the thrust than the rear one and they don't have seals near them. Also, crank journal surfaces are supposed to be as straight as possible-no taper of any kind-and so are the bearings. There had better not be any "wedge" oiling surface!!!!! The oil does spread in a wedge shape from the oil source-the groove in the upper bearing or the oil hole in the rod journal, but there is no physical shape to form a wedge, just two PARALLEL surfaces.

Usually used boats are pretty much bought as is unless there is a written (Documented) warranty. I know thats not what you want to hear.

Another question is why do you feel you need a new block. Can't yours be lined bored to straighten out the rear main that got hot. I imagine the crank is toast but if it was running I would think everything else is still OK. Hard to believe the only thing noticed was an oil leak though. Sorry. You didn't notice any loss in power? Sorry for your trouble. :(

Heat Cracks in Block
 

The block has serious heat cracks.

There was no noticable loss of power, it was running great up to the time I pulled the engine!

Hello Guys!!
The problem with the bearing you show is a lack of lubrication problem and the rear thrust surface is burned pretty bad. This is almost always a problem with pressure to the rear of the crank-some of you guys have given good suggestions as for what to look for. If you want to be positive you have no static load on the thrust bearing, just mount a dial indicator on the front of the crank (balancer, pulley, etc.) and with a screwdriver or bar, move the crank fore and aft. It should move as far as the thrust clearance you measured during assembly-you did measure and record didn't you?
The seal is incorrect and could be a leak, but even if you left the seal out, it does not affect the bearing lubrication unless you run out of oil from the leak. Many engines have the thrust bearing on a journal other than the rear and they work the same way this does and they have no seal near them.
Bearing surfaces, crank journals, and bearing housings are supposed to be PARALLEL to each other, except the oil groove(like the one in the top half the mains) when needed.

Main Seal
 

Federal Mogul states:

Special Marine Crankshaft Seals Available

The FEL-PRO® Marine Gaskets line offers optional timing cover seals and rear main bearing seals for reverse rotation engine applications. The standard engine rotation direction is counterclockwise (left hand) flywheel rotation. However, in certain engine installations (such as V-Drive) reverse engine rotation is used. Reverse engine rotation direction is clockwise (right hand) flywheel rotation. It is critical to determine engine rotation before selling crankshaft seals for a marine application. The two different types of seals have different helixes on the sealing lip to direct oil back into the engine, so using the wrong seal can actually direct oil out of the engine. Be sure you know which type your customer's engine uses when selecting crank seals.

Remember that propeller rotation is NOT always the same as engine rotation. Do not rely on propeller rotation to determine correct engine rotation.

Try this link.

http://www.federalmogul.com/felpro/c...ets/pg_55.html

Professional is a loose term
 

Looks like the "Professional" builder of this motor didn't know what the helix on the seal was for. He unfortunately told me he has installed numerous yellow seals on rebuilds that he has performed.

Beware Guys!!!!!!!!!!!!!

Re: Main Bearing Failure - Thrust Surface
 

The thrust surface on my freshly rebuilt mopar 340 went away after <1 hr. run time. After hearing many opinions and listening to a lot of advice I have developed my own. Did you check the crank thrust surface finish? My crank was heavily shot peened and ground .010/.010. The machinist did not kiss the thrust shoulders. The shoulders still have the rough shot peened surface. I think this roughness wipes away the oil film and allows metal to metal contact of crank face and bearing.I will return the crank to the grinder for his opinion. Just a couple of tenths off of each shoulder should give a 8-16 finish. I will keep you posted

Re: Main Bearing Failure - Thrust Surface
 

i have read this whole thread and it is really interesting and informative... AND between all the info presented i think you have cumulatively solved the problem...

the answer is in the multiple posts that describe the eagle crank radii issue.

we had this problem occur with a series of cranks and it took some time to figure out... what happened and what i believe has happened here, is that when the crank radius is too large it effectively seals against the corner of the bearing.... that is to say, ... you check your bearing clearence on the "flat" but at the edge/radius interface you end up with effectively none.

what this did to me/us was trap the oil in the bearing for a LOT longer than it should... i.e it was not allowed to flush out the sides, and overheated that bearing really quickly and failed an individual bearing randomly . the mains were the worst because of the smaller clearences. it is sort of the opposite of putting rods w/ too MUCH side clearence... where the oil gets out too fast...

on my motors i had to radius the edges of the bearings to match the radius of the crank and the problem disappeared like magic... and for the record that solution came from the clevite engineers to whom i was SEVERELY *****ing after the third apparently random failure.

lots of people here document the radius problem... so that tells me that is a real and genuine issue w/ these cranks... and i tend to agree that the rear seal rotation has everything to do with leaks as opposed to lubrication....

ide bet 20 bucks that that rear main edge is getting into the crank radius and both overheating the oil BADLY in that one bearing as WELL as not allowing the oil to get OUT of the back of it and oil the thrust surface... which is where that lube comes from... it would explain both surface failures precisely and ALSO explain why it was only that one bearing.

ide have never remebered this if you hadn't brought up the radius deal...

Re: Main Bearing Failure - Thrust Surface
 

Pantera28-650HP
Who do you have looking at this motor? I have had a lot of work done by Mike at Speed Performance Engineering
1205 Karl Court Suite 103, Wauconda, IL 60084 (847) 487-7223

Mike