Rear main bearing seized on crank....

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Toby W
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Rear main bearing seized on crank....

Post by Toby W » Sat Dec 01, 2012 5:21 pm

The rear main bearing on my MA decided to become one with the crank 35miles after a complete rebuild. It happened going 30mph in 3rd towing my empty Converto.
The machine work was done by a NAPA machine shop and the assembly I did myself. At that time the crank was checked out by the machine shop and the NAPA guy told me to go standard - so I did. The bearings came from Ron.
-Temp was 180
-Oil pressure was good.
...and yes, the oil galley lined up with the hole in the bearing.

Here are a few observations:
- all main and journal surfaces on the crank feel "groovy" when you run your fingernail across. Did the NAPA guy consider that in his recommendation to go standard?
- looking at the bearings - they look pretty worn to me after only 35miles of use, right?

So - I'm wondering - what went wrong here? If I remember right - the main caps are not original to the engine - they were missing when I got the block.... :|
With the main caps torqued down, the crank turned over by hand just fine when I built the engine...

Other than:
-Checking oil galleys
-Grinding crank and getting new bearings
what else comes to mind?

Here are the pics:
Image
Image
Image


Mains and journals
Image


Upper main close-up
Image


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Bill H.
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Re: Rear main bearing seized on crank....

Post by Bill H. » Sat Dec 01, 2012 6:24 pm

If the caps were gone did you fit the new caps to the block by line boring it? The bearing is seized but thank goodness not spun. It looks like you caught it quick. There is some metal transfer though. The crank will need to be checked, magnafluxed and probably ground. The bearing all look "wiped" which is not good at all with so few miles on it. The engine will still need to be completely disassembled, all oil galley plugs removed and preferably hot tanked and pressure washed. If it was not line bored my bet is that is your problem. Remember, just because it gauges okay by micrometer and Plastigauge does not mean once torqued down the caps throw the alignment off. Most shops do not like doing line bores on jeep engines.
Bill H.

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Re: Rear main bearing seized on crank....

Post by Toby W » Sat Dec 01, 2012 6:56 pm

Bill,
No- not in line bored. :(
Any experience with in line boring and crank grinding? - $$$ wise I mean...

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Re: Rear main bearing seized on crank....

Post by Bill H. » Sat Dec 01, 2012 7:06 pm

That is most likely the problem. Here in California the last shop I had do one was Reynold's Machine in Bakersfield and the line bore was $150.00. I don't remember the crank grinding but I seem to remember $150.00 also. My guess now is going to be somewhere in the neighborhood of $500.00 to $600.00 for line bore, crank grind and hot tanking and cleaning. Just a guess mind you :?

Just to add a little something. On the L134 it is not as easy as plugging the main bearing bore and calling it good. Each main bore size is different. The specs are: #1 main, 2.4995"/2.5000", #2 main 2.4895"/2.4900", #3 main 2.4795"/2.4800". I hope this helps. :)
Bill H.

"Each shall seek his own kind, in other words, a bird may love a fish but where would they build a home together?" Tevye, Fiddler on the Roof

1952 Dunbar Kapple M100
1953 Willys M38A1
1962 AMC M422A1
1965 Stevens M416B1 X 2
1967 Kaiser M715

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Re: Rear main bearing seized on crank....

Post by Mark Miller » Sat Dec 01, 2012 9:14 pm

If you do have it line bored, make sure they know how to do it on the L134. I had a shop do a rebuild on a rare wilson block for my gpw, they had it line bored and distroyed the block by doing it wrong.

Mark

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Re: Rear main bearing seized on crank....

Post by artificer » Sun Dec 02, 2012 2:08 am

What exactly did your NAPA shop do?
Did you fit all bearings using flexi or plastigauge?
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Re: Rear main bearing seized on crank....

Post by Toby W » Sun Dec 02, 2012 3:13 am

John,
The napa shop hot tanked, magnafluxed, bored, sleeved all cylinders, honed and complete valve job. The crank was hot tanked, magnafluxed and mic'ed.....

Mark,
Thanks for the warning - this is an original MA block and I sure want to keep it in my MA.

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Re: Rear main bearing seized on crank....

Post by Joe Gopan » Sun Dec 02, 2012 5:06 am

Was there any sign of fuel in the crankcase, a leaking fuel pump will wash out bearings in short notice.
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Re: Rear main bearing seized on crank....

Post by Marty, SoCal » Sun Dec 02, 2012 5:19 am

How does the rear main seal look?
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Re: Rear main bearing seized on crank....

Post by Wolfman » Sun Dec 02, 2012 6:38 am

I agree, the block should have been lined bored since the main caps were not the originals but the bearing scuffing does not look like an alignment problem to me.
If the caps were off center, the wear would have been to the side, near the cap mating surface with the block, on opposite sides.
If the main bearing bores were not round, the crank would have tightened up when the main caps were torqued if the bore was to small. To large a bore might not have been quite as obvious. This is where the Plasigauge would pay off.
The block side of the bores should have been straight, even if the caps did not fit properly
And what does main bearing bore alignment have to do with the rod bearings scuffing ?
Poor lube to the bearings ? Contaminated oil ? Dirt, fuel was mentioned or anti-freeze.
I noticed you have an early crank with the large dowel flywheel bolts.
The flywheel has been replaced or at least the dowels replaced.
Was this the original flywheel to the engine ?
I ran across and engine a while back the had been rebuilt but had a weird vibration at around 1800 RPM.
Before the vibration was figured out, the crank broke.
Seems the flywheel was not a match to the crank. ( Tapered dowel bolts in this case.)
When the flywheel was tightened down, the dowels tightened up before the flywheel was against the crank flange. It wobbled.
On the bench this was not obvious but had everyone scratching the heads once the engine was running.
Did not become obvious until assessing the damage in the aftermath.
It was hard to tell since the crank broke but the bearings looked like yours. Only worse.
On assembly, flywheel runout should be checked. No more than .008.
It's in the TM.
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Re: Rear main bearing seized on crank....

Post by Joe Gopan » Sun Dec 02, 2012 7:04 am

The crankshaft and the bearing caps need a thorough dimensional check. The engine has some non standard parts as evidenced by the non Jeep flywheel dowels.In my opinion this is a red flag.
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Re: Rear main bearing seized on crank....

Post by Chuck Lutz » Sun Dec 02, 2012 7:43 am

The bearings...all of them....look like crap. So what causes that?
1) Lack of oil pressure?
2) Wrong size bearings?

I agree that using the main caps from another block are the first red flag if they were not line bored for this block....

What can you do next?
Before delivering it to NAPA...(which may mean another botched job) find out if you can what happened.
1) Mic the main and rod journals YOURSELF....
2) Find out if the bearing shells are sized for not only the block, but the diameter of the journals on mains/rods.

Post what you find...there are a few professional mechanics here who have helped others out before. A friend of mine found out the problem with his motor that seized was REALLY simple....

Say the crank was .010 under and the rods were .020 under......now in his case, the mechanic mentally REVERSED those specs when he ordered the bearing shells. So he got crank bearings that were .020 OVER and rod bearings that were .010 OVER.....

Now that meant his rod bearings left .010 SPACE in there and the rods were flopping around on the crank....but the main bearings were .010 OVER and the crank was only .010 UNDER which mean when torqued down his motor siezed up as soon a HEAT/EXPANSION got to work!

Simple mistakes like that make it easy to screw up things....do a little checking and get back to the gee with results...
Chuck Lutz

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Re: Rear main bearing seized on crank....

Post by dpcd67 » Sun Dec 02, 2012 10:32 am

One easy check after you assemble the bearings is to see if the crank turns without too much effort. If it doesn't, you know that something is wrong, like wrong bearings or mis-aligned caps. This is regardless of what measurements you take. After all, as stated, you can have all the right specs, and still have an assembly mistake.
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Re: Rear main bearing seized on crank....

Post by artificer » Sun Dec 02, 2012 10:56 am

Indications are that the main bearing caps may be aligned OK or fitted as there is no real evidence of such "non alignment" in the pictures
This tunnel bore is something NAPA should have checked & if out should have locked up the shaft as you fitted the main caps.

I agree all the bearings should not look as they do after such a short run. The engine in my opinion has been assembled dirty....evidenced by the dirt & muck embedded in some of the bearing shells.

Marty asked the primary question that needs answering, about the rear oil seal.

It appears the rear main bearing journal then it's slipper bearing shell has been so hot it melted @ the rear whereas the front of that bearing except for dirt & scuffing seems to have had some clearance. Indicative of an overtight rear main seal that should have been more than obvious when trying to turn the engine.

The pictures especially the first couple indicate the possibility that the slipper shell may not have been fitted correctly as you have them layed out with the main oil feed hole to the RHS. The oil feed in the block is on the LH or cam side.

It is possible to fit main bearings wrong way round & block off oil feed to the main bearing as the oil hole in the shells is only on 1 half [a very stupid unnecessary design feature & trap for young players].

Whenever assembling an engine you should check all bearing clearances using micrometers or plastigauge, if you want things right. Can be a very expensive exercise otherwise.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Rear main bearing seized on crank....

Post by Bill H. » Sun Dec 02, 2012 1:23 pm

This doesn't look like an alignment issue to any of you? Wow!

Also, wiping is from only a couple of things, lack of oil at either initial start up or revving a cold engine with no oil pressure. Look close guys at the uneven failure again. It screams alignment issue to me and my reference books. I do wish Mike Wright would pipe in about now. He had this same issue a while back on a brand new rebuild. The crank turned free when all the caps were installed and torqued.

And yes, the rear seal needs a good looking at.

Image
Bill H.

"Each shall seek his own kind, in other words, a bird may love a fish but where would they build a home together?" Tevye, Fiddler on the Roof

1952 Dunbar Kapple M100
1953 Willys M38A1
1962 AMC M422A1
1965 Stevens M416B1 X 2
1967 Kaiser M715

2 Timothy 3:1-5


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