Correct Rod Bearing Inspection Procedure

[BarbaratheIrish2002]

I want to preface this by saying engine is still in the car, oil pump and oil pan are removed, subframe is lowered.  

 

I have a Haynes manual but it's short on detail for rod bearing inspection. What is the correct procedure?

 

Specifically, where should the piston in the cylinder in question be? TDC? A little below TDC? 

 

Is it a simple matter of undoing the two end-cap nuts, removing the end-cap, inspecting the bearing, checking the crankshaft at that point and then retorquing both endcap nuts before moving onto the next cylinder? For this initial visual inspection, I just want to have a look at the lower half rod bearings.

 

This may seem like a blatantly obvious question to ask, but I trialed the removal on cylinder one using this technique (while cylinder one was at TDC), the nuts came off, the end cap is loose and shaking about a little but try as I might, I could not get it to come all the way off. Also, at TDC, the piston is obviously as far up into the cylinder as it goes, making the removal of the endcap that much more difficult...but I did see elsewhere it's not a good idea to have the piston all the way at the bottom of its stroke either, lest some rings let go. 

 

Anyway, maybe I just need to be rougher with the removal of the end cap...but maybe there's another trick I'm missing out on. 

 

Again, thanks in advance for something that is likely bread and butter knowledge to you all, but it's a learning experience everyday for me with the M10!

Edited September 9, 2022 by BarbaratheIrish2002

[Son of Marty]

The crank position really doesn't make much difference, I would avoid hard tdc or bdc because sometimes a bit of crank rotation can help free the cap. Otherwise what ever allows the best access to the rod cap.   

[TobyB]

I use BDC and a BFH.

 

Take the BFH and use the end of the handle to tap on the studs 

to break the cap loose.  The studs have a centering diameter up

towards the top, and this is a slight interference fit sometimes.

 

I start with #3, as it's usually the worst news.

 

Cleanliness matters in this process.

 

TLA's FTW!

 

t

 

[Hans]

A light but firm tap just to break the initial seal. Be VERY careful not to let the treads touch the crank surface. Plastic tubing works nicely

[bergie33]

I am by no means an expert, but my thought is to throw some plastigauge between the bearing and crank to check the clearance.  The bearings and crank might look good, but be worn too far.  This will let you know if there is more work to be done.  OK experts, let me know if I'm not thinking about this right.

[tech71]

14 hours ago, BarbaratheIrish2002 said:

I just want to have a look at the lower half rod bearings.

Not sure I understand your motivation here...

Visual insp won't tell you much unless there is severe wear or damage of some sort.

Plastigauge is cheap and can be helpful in determining clearance/wear.

Also, with a bit more careful effort you could install new rod bearing shells, you're already in there.

Edited September 9, 2022 by tech71

[BarbaratheIrish2002]

12 hours ago, TobyB said:

Take the BFH and use the end of the handle to tap on the studs 

to break the cap loose.  The studs have a centering diameter up

towards the top, and this is a slight interference fit sometimes.

 

I start with #3, as it's usually the worst news.

 

Thanks @TobyB. Two questions...

 

What is BFH?

Why generally is #3 the worst? Some sort of design oil flow issue?

Edited September 9, 2022 by BarbaratheIrish2002

[BarbaratheIrish2002]

17 minutes ago, tech71 said:

Not sure I understand your motivation here...

@tech71 Yesterday, as the sunlight was beating into the garage just right, I noticed that there were a small amount of reddish specks in the very bottom of the oil pan. Very small amount. To the point it could be something else, or, it could be copper from a ruined rod bearing. I want to see (visually) if the rod bearing surfaces have degraded to that point. I'm not going to the work of pulling the top half bearings if the bottom ones are ruined (then I've a much bigger problem on my hands that'll require much more work!!). Pulling the top have ones increases my risk of scratching the crankshaft surface and making the whole thing worse. And it offers no more insight that what I'm after. The bottom ones are easier to remove (and someone can correct me if I'm wrong, generally have more wear?). 

Edited September 9, 2022 by BarbaratheIrish2002

[Mike Self]

BFH=Big f---ing hammer.  Or you can use a small copper or rawhide mallet to tap the rod bearing cap loose.  They are--and should be--a tight fit.  Just be sure and replace it (and its bearing) in the same location (i.e. don't swap ends). 

 

Number 3 is the last bearing to receive oil from the gallery, as #4 is fed from a gallery that doesn't include 1, 2, and 3.  IIRC it's fed from the same oil gallery that supplies the camshaft and rockers, from the rear of the engine, while the front three rods get their oil from a gallery at the engine's front end.

 

Plastigage will tell you if there's excessive wear; your Mk 1 fingernail will tell you if there's excessive scoring on the journals.

 

From experience with my '73, after dismantling the 204k mile engine, crank journals were well within tolerance for standard sized bearings.  I only swapped cranks because I had another with no measurable wear that had already been polished.  I kept the original crank to replace the 6 bolt crank/flywheel when I have to rebuild it.

[TobyB]

Mike, ya stole my thunder!

 

I like a visual inspection, too, as the upper shell tells a 

story of the conrod, detonation, and oil change interval.

And at that point, a new set of rod bearings is a quick and

cheap 'refresh' unless the old ones are brand- new looking.

And measuring.  As of last month, a set of KS rod bearings

were both available and priced well.

 

But then I usually just cut to the chase, yard the engine, measure

and replace the pistons, and whups, it's a full overhaul.

 

t

[jireland2002]

For about $35 you can send an oil sample to a lab.  I got a kit on Amazon recently.  Very easy.

[Son of Marty]

Wouldn't a oil analyst be easier and more informative?

[Hans]

plastic tubing.

[Mark92131]

I have a related question for the experts in this area.  I need to swap in the special center main cap that supports the oil pump pickup on the M10 to my S14 motor.  Is is as easy as unbolting the S14 center main cap, removing the bearing shell, installing it in the special M10 main cap, and bolting it back in the S14 with the longer M10 main cap bolts?  Are there other things to consider?

 

Thanks,

 

Mark92131

[Mark92131]

48 minutes ago, Mark92131 said:

I have a related question for the experts in this area.

 

My bad, it looks like the support bracket just sits on top of the cap, so no need to pull the cap.

 

Sorry,

 

Mark92131