signs of rod bearing failure?

My F 134 is freshly rebuilt. But lacks power and is starting to make a heck of a knocking sound. Tonight I pulled the oil pan off for a look. I can't see anything wrong visually. The side to side play of the rods on the crankshaft maybe a tiny bit loose on #3 but otherwise no metal filings, nothing broken I can see.

Can you see anything wrong if its a rod bearing failure?

 

How's your oil pressure?

 

Did it have more power after the rebuild, and now it's gone down? Power loss and knocking sound like it might be two different issues...first thing I'd check is the timing, and as Rondog noted oil pressure.

 

And sometimes, if you remove one plug wire and ground it, then crank it up, and knock still there then do same thing to next one. If knock ceases when you get to the right one, then likely it rod bearing.

 

Yes, you cannot see anything typically.

Oil pressure is vital. A change in oil pressure would indicate a problem.

You can take the caps off and look at the rod bearings. You'll need a torque wrench to put them back. You can measure the clearance in place with Plastigage - squish the Plastigage between the cap and rod, remove the cap and measure the squished width.

 

Oil pressure has not been a problem. I had the engine rebuilt prolly less than 10 hours of running time ago. Drove it twice for a couple of miles to test it out. Rest of time on engine has been in the shop trying to figure the no power problem out.Never has had great power, the knock started a bit ago faintly and I thought it might be timeming, or vacuum, checked that. Knock suddenly got much worse. Stethoscoped the knock seemed to be close to #2 cylinder.

Side to side play on the #3 cylinder rod at the crankshaft seems a smidgen looser than the rest, feeler gauged it at .254mm just over tolerances.

What to look for when I take off the cap?

Thanks guys for your help.

 

Take a look here:http://mahleclevite.com/publications/CL77-3-402.pdf It's a big pdf download but takes you all the way from theory, appearance, causes, and corrective action. HTH

 

Excellent 8)

Click. Save.

 

It would seem to me that with only 10 hrs on a rebuilt engine, the re-builder should be the one doing the diagnosing. Have you done a compression check re: the lack of power?

 

Posimoto, you are right, the builder should be doing it. But I moved since I had it done and the builder is quite a ways away and with my work schedule it will be months before I can get it to him when he's open. So I called him and he said to go ahead and pull the oil pan to see what I can find and let him know.

Compression is good across all 4 cylinders I believe it was 120 last time I checked.

 

sidscj,

thanks for the bearing article, that's a lot of information!

 

I bought a 304 off a guy that said it lack power. Engine idled fine and the guy took it to several shops to dianose "lack of power" problem. After no luck fixing the problem he bought a 360 to swap. After unhooking everything except the fuel line he found the problem: kink in the fuel line. Anyway the 304 ran great in my CJ. Moral of this post is: Check fuel line for kinks and blockages.

 

Just pulled the #2 cylinder rod bearing and... Dang! alot of scoring for a 10 -20 hour engine.

 

Could the above bearings cause a knock? Power loss?

 

knock for sure.

 

I would send those pic's to the guy that did the rebuild and see what he sez. Sure looks like your gonna need a new crank kit?

 

Absolutely causes the knock. Toast. No question. Don't drive it.

Power loss is a different question - but you have to fix the rod bearing first.

 

ive seen bearing with over 100000 miles on them in better shape than that would most definetly say you found the knock, would pull the rest to see what they look like

 

looks like crank is gonna need resurfaced also

 

My plan tonight is to pull the other three and inspect. Might try to polish the crank in the vehicle, but if that fails then pull it and take it back. Now I need to try and identify the source of the dirt or metal or whatever did this. As I remember there were a few metal shavings in the oil pan after the first 30 minute break in period. I kinda thought that was normal for a new engine but mebbe not. Changed the oil and oil filter after the first 30 min, then again after about 3 hours running time. Hmmm?:?