Farmall c knocking?

[Zsprankle]

Hey guys, first post here. 2 years ago I gave my 1948 Farmall c a freshen up, tore just about everything down behind the bell housing with all new seals gaskets.. etc, I didn't touch the engine because I had been into it a handful of years back and everything looked good and it ran great, long story short I got her all painted and freshened up the summer before last. I was brush hogging with it at the end of last summer when it didn't lose oil pressure but slowly dropped to nothing within about an hour of mowing one day, so I stopped and put her away only to tear her down last winter to find the rod and crank bearings were severely worn, plus the oil pump cover was shot. So with the help of my machinist father, I got them measured up and rolled in some new bearings and refinished the oil pump plate. Everything was within spec and got put back together, some running, no hard work and an oil change later, she's back on the mower, problem still persists although not nearly as bad. On first startup when the oil is cold she holds 65 pounds of oil pressure at full throttle, it takes about 10 minutes of mowing to the the oil warmed up and then she's down to a steady 45 to 50 all day long no issues there. The problem comes when I idle her down, I think it starts knocking although it still holds oil pressure, granted not very much. I'll attach a video of what's going on, I think it might be time for a new oil pump plate, because I think that one may be warping when hot but I don't know, and input is appreicated, thanks.
https://photos.app.goo.gl/EdPiCkETdxC9hoPF9

 

[Moonlite37]

I would think there is something else other than main or rod bearings. Your oil pressure is perfect. I knew a fellow who could tell a bearing knock from a wrist pin knock by sound.All knocks sound the same to me. I was thinking it may be a pin, but I do not thing you have a rod or main knock by the excellent oil pressure.

 

[Dave BN]

Does the knock seem to be at crank shaft speed or cam shaft speed? It could be something in the governor or maybe the fan bearings. I had a fan go bad and I thought for sure I had a rod knocking. Maybe walk around the tractor and listen. Maybe use a piece of wood dowel held against your ear and against various engine parts too locate where the knock is coming from.
Dave

 

[Brown Dirt Cowboy]

years ago when I rebuilt the motor on my '45 B i did not properly torque the 4 bolts to the pressure plate and they loosened up and cause a knock. Hope your problem is as simple as this.

 

[redforlife]

When you rolled in new rod and main bearings, what did the crank look like??? Just as bad as the old bearings you took out?
A rough crank, could probably make your new bearings look like the old ones in pretty short order. Hope that's not your problem, and you were on top of that at the time of that freshen up. If your machinist father looked at the crank at the time of that dis-assembly, I'm guessing he would of known the difference between a usable crank, and one that needed to be turned down. But, ... I'm not sure how much inspecting you had him involved in. Just measured your old bearings, or looked at all of it.

If you've had no less than 45 lbs of oil pressure since the installation of the bearings, then oil pressure itself isn't your problem this time around. But, might have something to do with how you put it together, or what you maybe didn't do and should of.

 

[Steve@Advance]

Sounds like it has plenty of oil pressure. Very normal to have low pressure at idle. If there is any needle movement at all at idle it will last a long time.

Something you can do, with it at idle, warmed up and knocking, pull one plug wire at a time, listen for a change. If the knock stops, chances are it's a loose piston or wrist pin. If it becomes a double wrap, suspect a rod bearing (but I doubt that since it still had oil pressure). Piston/wrist pin noise can go for years without causing problems.

If there is no change, it could be valve train noise (the valves should be readjusted anyway when they have been apart). It could also be a loose front pulley or a chipped tooth on the cam/crank gear. Also try a start up with the fan belt removed.

 

[rustred]

sounds like a worn out engine to me. plus engines should never be at the slow idle unless u are shutting them dowm. always idle them 800-900 rpm. engine wear happens at slow idle and start up. and a worn pump and brgs is not going to let you keep up the oil pressure as in a new engine. so either idle it up plus use thicker oil.

 

[Geo-TH,In]

My Farmall C doesn't knock at an Idle.
And if it did, I most likely wouldn't hear it, bad hearing.
My oil pressure gauge is next to the oil filter.
The gauge is pegged to the right, full oil pressure at idle or running.
I use 10w40 regular oil.
I change oil every two years, est 100 hours. It doesn't use a drop of oil.

 

[560Dennis]

Mine knocks at idle .
Ask a tech at case ih ,he said push clutch in . See if the makes a difference. They said they have had some broken crankshaft in past and they still ran .
Also active the touch controls does it change sound ?
Just couple of things to consider troubleshooting.

 

[Zsprankle]

Thanks guys, I've considered all of your replies, truth is, I don't idle it down like that normally but it does make this noise when I shut it down, because I'm familiar with engines it drives me nuts, can't be valve train noise, I adjusted the valves roughly 100 hours ago and there was nothing like that before, plus when you put your ear up to it the sound comes from the bottom end, hydraulics don't make a difference and putting the engine under load makes the noise go away( I think it may possibly be still there but not as loud). When I rolled the bearings in I had my machinist dad measure the crank at the rod journals, (as you can't get to the main journals accurately with the crank in) and the measured within spec( don't remember as it has been a while) but all the journals plastigauged just fine, and I will have to try removing one plug wire at a time but I know the noise does come from all 4, thanks for all the input, I was thinking really seriously abojt tearing it back down this winter but an not thinking so hard about it

 

[Zsprankle]

They all sound the same to me but I never thought about it that way

 

[Zsprankle]

None of that makes a difference for me

 

[Zsprankle]

I usually never idle it down that low, but I am using 15w40 oil so no oil problems here

 

[Zsprankle]

I know exactly what you are saying and have never thought of doing that but I definatley will now, as far as that valves go they have been adjusted within the last 100 hours and it sound like the noise is coming from the bottom end so I don't think it could be the valves

 

[Zsprankle]

I don't know how to explain any better on my end, if you put my crank and a brand new crank sis by side right out of the parts washer I don't think I would be able to tell the difference just by looking the the journals, I was actually kinda surprised at how nice it looked, and I can guarantee you that everything is put together how it came out

 

[Zsprankle]

I didn't even touch those bolts but I
guess it wouldn't hurt taking a look up in
there

 

[Zsprankle]

I've never had much luck using a dowel or screwdriver but you made me think, my dad has a mechanics stethascope I might be able to pin point the sould a little better