Half of a cotter pin in oil pan?

[bkensinger]

This summer when I did an oil change I found half of a cotter pin stuck to my magnetic drain plug. I had the engine rebuilt 4000 miles ago and presume the cotter pin is off one the connecting rod nuts. Should I let this go or drop the pan and find and replace the damaged cotter pin?

[katy]

I would drop the pan and.................

[Joop]

I agree with Katy
Better safe then sorry!

[tinkirk]

Ask your engine rebuilde


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[DBrer]

Yikes! I would wonder why it would even come out. I would pull the pan.

[ryanheacox]

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Better to drop the pan now rather than after that rod nut backs off.


Surprising it found it's way past the dipper tray, lucky. I'd change all the cotter pins while you're in there.

[Jim Brierley]

Cotter pins really don't hold the nuts in place, so are not needed. I never use castellated nuts, just plain, good quality nuts, no pins or loctite.

[Chuck Sea/Tac]

Jim is right. Not that I am a engine builder or anything. I just did a 40,000 mile bearing tightening on my engine. It was just as Jim said nuts no Cotter pins. The other thing is it was a half a cotter pin. So the other half is still in it. It probably broke when he bent it over You’re wasting your time taking it apart.

[Kurt in NJ]

If the cotter pins are not cinched tight they will rattle and wear through

[George Miller]

They do not use cotter pins on new cars. Use really good nuts torque to speck and for get it.
Now if I do some one else engine I use the pins, other wise they would bad mouth you.

[Joe K]

Um. Cotter pins are the belt to go along with your nut suspenders.

And new cars generally don't use cotter pins but they do use various other "retention" schemes including Loctite, inserts, prevailing torque schemes, upset threads. I would guess with one known exception those that use nothing and rely on bolt tension alone are none.

The VW TDI of my former affections used "stretch bolts" which TECHNICALLY must be changed for new on each re-do, but most who work on their TDI diesels never do (Including VW Dealerships) instead relying upon Loctite Blue and perhaps half the near 300ft-lbs of torque required to set the passenger side engine mount bolts (necessary by design to change out the timing belt - not one of VWs most intelligent designs.) Without a calibrated air wrench one runs the risk of knocking the car off the jack-stands trying to achieve that 300ft-lbs "the old fashioned way."

I myself have told my story of the Model A engine which was SERIOUSLY egg-shaped in the crank. I had shaved the caps several times and finally took to the expediency of filing to the point where the rod caps "just bound" as one passed certain pressure points on the egg-shaped rod journals.

Driving the Mid-Cape Highway at the then maximum speed of 55 all of a sudden the engine started to make a terrible racket. So I slowed down and let the traffic pass me by. Fortunately I was not far from my home and limped home not pressuring the engine in any way.

On disassembly, I found the cotter pin in pieces in the oil pan, and the loose nut alongside. The rod was being held by ONE nut.

Of course in "wearing in" that engine I created a situation that the vibration wore upon the cotter pin and caused its demise, followed by undoing of the nut. This was a nut which was "snugged up tight" to begin.

So as an Engineer I can appreciate Jim's comment (above) where local distortion can bring a connecting rod nut to that "near prevailing torque" condition - but I'm not sure I would wish to count on that alone.

If it's any consolation to the board, I do own both belt and suspenders - but I NEVER wear them together lest I be accused of being "that sort of guy." But the rod nuts in my engine are not seen so perhaps it doesn't come to mind of observers?

Joe K

[28Danby]

Originally Posted by Kurt in NJ

If the cotter pins are not cinched tight they will rattle and wear through

It also works the other way as well. I've seen plenty of weakened cotter pins that people wrap around nuts and bolts thinking they need to be tied like tie wire. A good stainless cotter pin with a slight bend in it is all that needed. It doesn't need to be tied like a hockey skate.

[Jacksonlll]

How long is the piece? If it's less than a quarter inch, you are probably OK..

[Jim Brierley]

Back in the 50's I was a mechanic at a GMC dealership. Another mechanic had rebuilt a 503 engine. A few weeks later the owner brought it back to the shop because he had drained the oil and got a handful of broken cotter pins. The foreman gave me the job because mechanic #1 was on vacation. Not one of the rod nuts were loose, not even one! The problem was caused by the mechanic not driving the pin in with a hammer to
fully seat them before bending them over.

When A & B engines were being raced, the Ford rods had a bad reputation, and many aftermarket rods were made. I believe it was not the rod, it was the castellated nuts which have only 3 or 4 full threads, and they would strip-out. I raced Model B's for many years with B rods, but Cat or ARP nuts, never a problem and consistently turned the engine 6,000 to 6200 RPM.

[katy]

Anyone use PAL nuts. Ford used them for many years on the flathead V8S. Methinks there' still some in the bottom of one of my tool boxes.

[Joe K]

My engine rebuilder chose "Nylock" type nuts. Plus he says "You can use a standard wrench on these."


Joe K

[Joe K]

Originally Posted by Jim Brierley

Back in the 50's I was a mechanic at a GMC dealership. Another mechanic had rebuilt a 503 engine. A few weeks later the owner brought it back to the shop because he had drained the oil and got a handful of broken cotter pins. The foreman gave me the job because mechanic #1 was on vacation. Not one of the rod nuts were loose, not even one! The problem was caused by the mechanic not driving the pin in with a hammer to
fully seat them before bending them over.

Not to confuse but slightly after the Model A era was the development of "hammerlock" cotter pins. The head and far end are made such that they can be hit with a hammer while in place, and the act of hitting cause the two parts of the cotter to "set themselves" in place and create an interference.

It was a development ostensibly to shorten assembly time - no need to use a pair of pliers to bend carefully the legs of the cotter in different direction. A quick hammer blow (it was thought) and assembly was done.


Now perhaps you were doing both, setting the pin AND separating the legs?

OBTW, hammerlock pins are one of the things judges look for to mark down on. IIRC No Model As were produced originally with hammerlock. Check your front end.

Joe K