Noise in engine-help please

[Denis]

Hello all, I hope that someone may be able to help. My Cub has started making a light knocking noise in the engine. I cannot quite make out if it is more in front or the back, but it seems to be in the area of the camshaft. The strange thing is that although the oil pressure is good the needle fluctuates up and down at the same time as the knock. It seems more pronounced at idle that higher revs.
I have drained and replaced the oil and filter. Also removed and checked the oil pressure relief valve which seems to be ok.
Any thoughts as to what it may be. I am thinking maybe oil pump problems.
Thanks, Denis

[Bigdog]

Denis - oil pump problems is a definite possibility. Unfortunately, I think the only way you are going to know for sure is to tear it down and have a look.

[John *.?-!.* cub owner]

This is one of those things that is hard to diagnose from long distance. As Big dog says, oil pump is a possibility, but for a cub oil pump to fail is rare. Even though it seems to be coming from the cam area, I would be more inclined to suspect a rod bearing going bad. While it's running try removing the sprk plug wires one at a time to see if that changes the knock. If it does, it's most likely a rod bearing, if not may be oil pump or cam shaft. Did it start suddenly, or build up slowly.

[nosih]

I would agree with John that it may be a loose rod bearing, but you may also want to check and see if the valve lash is in correct adjustment.

I have a Super AV (granted OH valve) that before it was overhauled, had a knock in the head. After tearing the engine down for an OH, I noticed that the rocker arms had been beating the valves so hard due to being out of adjustment that the face of the rocker arms were indented. needless to say all NOS rocker arms in that engine. The crankshaft clearances were within spec and the piston pin to pin bushing clearance was in spec also. Now afer a complete OH (NOS pistons & Sleeves, NOS cranshaft & bearings, NOS valves, NOS rocker arms & shafts, and all new transmission shafts & gears) this old neglected tractor is running perfectly.

[Eugene]

My initial thought is that one of the main journals is out of round - pulsating oil pressure - or a rod or main journal/bearing is going bad. Before tearing the engine down I would check the valve lash - valve action and engine timing. I would try to isolate the knock.

[ScottyG]

You'll all think I'm pretty strange with this one but I thought that I had an engine knock as well. I could hear it very pronounced while at idle. I scratched my head because the engine runs strong, has good compression and didn't make a sound when I first bought it. Turned out to be a loose clutch throwout bearing which kept slapping against the clutch plate from vibration.

Just something to consider...

[Bigdog]

Internal noises of any kind are really hard to diagnose. Especially over the internet. Sometimes you just have to hear it for yourself.

[Slappy]

Speaking of noises that were hard to find, I had an odd, high pitch whine suddenly appear when the engine was throttled up. It sounded for all the World like it was coming from the Touch Control. I flushed the HyTran with no good result. I was about ready to tear the whole thing apart, when I discovered that the linkage rod had come out of its retaining clip leaving the rod free to vibrate againist the dash panel.

Oh well, the TC probably needed a good flush anyway.