engine and drivetrain Engine Builders With Knowledge: Crankshaft End Play

[PatAllen]

Hi, i am dealing with a random knock at idle on my Automatic 02, tonight i decided to take the engine apart and inspect its inards.

I was suspecting con rods small end bushings since it makes the noise only at idle, hot or cold so i rulled out crank and piston slap.

 

once all apart everything seems in perfect condition, no rod play, all is new in there. The only odd thing is that there is a lot of crankshaft axial play, far more than the prescribed  (3.3 to 6.8) thou, maybe 60-80 thou.

 

So, how in the hell would someone correct this ? simply change the crank ? is there some kind of overside trust bearings for the crank on the M10 ??

 

I was wondering about melting some lead over the trust side of the bearing and file it down up until i get the proper clearance/width...

 

thanks for any advices.

[TobyB]

I'm guessing it's rebuilt?

 

Usually, the thrust bearings are oversized in the 'thrust' direction as well as being made for a smaller

diameter journal.  There are some aftermarket ones that are not, and so if the grinder does the

'usual' grind for an undersized crank, things don't work so well.

 

But that's pretty unusual.

 

Especially on a freakin' AUTOMATIC!  This is often a problem for manual M42's, where the thrust

bearing is only on 1/2 of the circumference of the bearing...  but not M10's.  They're plenty stout.

 

As to making your own bearing- sure, why not?  If it's all shiny, it should be fine on an auto where there

is very little end thrust anyway.  Just get the crank in the right place for the rods, and it should work fine.

 

If you want to do it scientifically, take an old bearing and heat it slowly to find what the melting point of the

babbit is.  Then mix up your own with a lower melting point, heat the bearing up to that, and schloop it on.

 

It's not easy, but for the thrust surface, why not?

 

Odd.

 

t

[PatAllen]

i found out "king engine' bearings, they offer larger/oversize bearings just on the trust side.,...

 

http://www.king-bearings.com/cat/ViewSet.aspx?king_set=CR4264CP

 

i guess they buy new bearings and do exactly what i am expecting to do...

 

How about the bearing cap in itself, there is some loosenes that can be used to "bind' the cao aft/forth i guess to force the shels to be offseted maybe 6-10 thou....i know on the M42 you must push on the cap before torquin it....

 

 

thanks !!

[eurotrash]

when I built my motor over the winter, I had to swap in another crank for just this reason.  I was as if someone had been drag racing the car and dumping the clutch...   over and over and over and over and over and over

 

It was bad.  interestingly, my car was originally an automatic.

[WVGranat]

My relativley low mile short block (unrebuilt) was at one time in an automatic, and I too have the exact noises that Pat describes.  Everything else checks out (I too suspected crank or rod bearings) just have not had time or the inclination to do anything about the crank thrust slop yet.

 

Perhaps the auto puts some strange load on the crank during upshifts?

[TobyB]

The transmission really can't load the crank, if everything's installed and dimensioned properly.  Hmm, wonder what's going on?

 

t

[PatAllen]

among all the things i did read, i noticed that in some cases, on other kind of car (GM iirc) the torque converter can "bubble up" and then push on the crank....cant tell if thats the case, also this actual crank came from another 02, manual so i cannot relate this only to the fact that it was automatic before.

 

I made an attemp on a used bad bearing to see what i could do...

i added +1mm (0.5 on each side), milled it down and sanded it off with 800 gritt...doesnt look bad for a first try.

still not 100% sure it the knock sound was coming from that excessive play...

[percy]

My relativley low mile short block (unrebuilt) was at one time in an automatic, and I too have the exact noises that Pat describes.  Everything else checks out (I too suspected crank or rod bearings) just have not had time or the inclination to do anything about the crank thrust slop yet.

 

Perhaps the auto puts some strange load on the crank during upshifts?

 

 

There are noises and there are noises.  Some may sound alike, but not all eminate from the same source. 

 

I encountered a similar noise on a high mileage '73 auto-trans model.  Everything seemed just fine except for the noise, which appeared at idle. but mostly when things were at operating temperature.  Sound did not seem to come from the valve train.  My initial reaction was long term wear and low oil pressure.  Oil pressure tested normal and with no oil burning, excellent compression and decent performance and fuel economy, I was reluctant to tear into it.  I did try adding a three-letter viscosity "elixir" that may have had a slight quieting effect. Curiosity got the best of me.  Ended up dropping the pan and discovered the oil pump chain had substantial amount of slack.  Instead of shimming the pump I replaced the masterlinked chain with another.  I did not replace the corresponding drive gears.  Noise gone.  

 

I do not pretent to say that excess lateral crank journal wear or crank bearing wear did not exist.  But with the noise eliminated, I felt no reason to tear down further - especially with the engine in place.

 

It's been a long time since I poured my own babbitt (for something a lot older than the '02) but I see no reason why it couldn't be done.  Primary reservation would be replicating a long wearing alloy versus a hit-or-miss home brew. 

[PatAllen]

for now i dont have babitt, i am using 63/37 allow. i know its far from what it is needed but i cant find any local that sells babitt, they dont even know what it is...my goal was to see if i was able to add material just on the edges without affecting the bearing itselft, which proved to work.

 

on a similar topic, how about piston knurling techniques/know how? i just did some test on a used worn piston and realised its now super stiff, so i need to file down the edges of the knurls. i have read somewhere that one would leave it like that and since the knurls are light/soft they wull wear down and the engine would get proper clearance on its own (!)....

this is far from being a scientific method but with a lathe and a hand held knurler it worked...

[PatAllen]

here is the knock sound in all its glory 1 minute before i tore down the motor completely. as you can hear i release the throttle the knock is heard, and few seconds before the video ends, you can hear it coming along on its own and louder, toc toc toc toc...

 

 

i scientifically measured the play and it is at 0,040" 

 

i am very puzzled for now, i took out the bearing shell and it is used a lot, just like if the TC was pushing on the crank (bubble up effect under a given circumstance, maybe under acceleration where the pressure is high, i dont know)

[PatAllen]

i have to correct myselft, i measure the endplay in mm so it was 0,03mm, that makes 11thou, which is still the double of the permitted maximum...still very puzzled about the level of the knock it was making and what i actualy "didnt" found this much wrong...

[percy]

Couple thoughts.  Here is a source for babbitt material:  http://www.rotometals.com/Shipping-Rules-and-FAQ-s/79.htm  There are many others if you do a little searching.  I wouldn't be surprised if you could harvest some of the alloy from a few other sacrificial bearing shells.

 

I listened to your knock.  While it sounds like it could be a rod, in my limited experience with that specific problem, it typically gets worse and can be heard throughout the rev range.  It's too bad you didn't try one of the traditional checks.  Pulling each plug lead,  one at a time,  to see if the sound disappeared or abated.  This has the potential benefit of confirming that the sound was part of the piston-rod assembly and narrowing the search for the sound. Another diagnostic tool is to use a timing light on each lead until the light is synchronized with the knock - to narrow the noise to a specific piston-rod assembly.

 

 

"Piston slap" generally occurs with a cold engine and often can be described as not-unusual with forged pistons.  Sounds somewhat similar to a diesel.  Your video does not sound like piston slap.  Another possibility that you did not mention is piston boss wear around the wrist pin.     

 

 

In some ways, the sound reminds me of the chain "slap"  I described in another post.  In that case the noise was most pronounced at idle.  The sound may have been drowned out by other engine noises with increased speed or the noise actually decreased with speed.  I just can't recall.  Not saying you should ignore the apparent out-of-spec wear you found, but its something else to watch for. 

 

Best of luck.

Edited August 6, 2014 by percy

[PatAllen]

fwiw the noise is absent when the engine torques and/or is above 1000rpm. it realy makes it only upon deceleration only just before it reaches idle.

when i used to work/rev hard the engine, it just purrs like a kitten all the way thru the rev range.

 

the oil pump chain was indeed a bit slack, maybe 1/4 of an inch side to side, and doesnt appear to have touched ever the cover. new chain, new sprockets and shimed accordingly when i did the rebuild.

 

one thing i noticed, it started to make it louder right after an oil change. castrol 20w50 and zddp additive...nothing unusual there...

 

Thanks for the added info m. percy.

[PatAllen]

here is my very first attemp to make piston knurl...after filed down, i can get near zero gap in some cylinders so now i know there is at least one cylinder with a bit more slack hole....1-2 thou maybe. it certainly works and certainly debatable as to be a good idea or not. as once stated by someone in a mgb forum, he never heard bad horror stories about knurled pistons...

Edited August 6, 2014 by PatAllen

[Simeon]

Seen piston knurling done successfully on Land Rover engines along with fresh rings and a hone. Not sure of the limits in terms of clearances where advice says it should or should not be used. I can imagine it is the sort of thing that the Germans would frown upon but it sounds like you are having a bit of fun with your experiments rather than try and build a factory smooth 'like new' engine.