Frustrating Oil Pressure Issue

[Soundguy]

good question

 

[8envy]

Well, I wish I had but, I did not run the tractor before pulling it apart mainly because it was a mess. I did check compression though, it was lower than I would have liked... 75-80pounds. So I can't say if it is a new noise or not. I can say that when it was running and under light use about 12 years ago by my grandpa, he probably wouldn't have noticed the noise. I was 13 years old at the time and didn't care about tractors. Ha.

UPDATE: I was able to get out to the shop tonight to check a few things. Upon cold start up (room temp was 35F) the oil pressure guauge was pegged at 50psi !! (SAE 40W oil) at idle or just above idle and it was beautifully quiet. With the enging probably just below running temp, pressure has begun to fall to about 30 psi and still falling. 15 minutes run time and now she's showing south of 20psi just above idle. The engine knock is now noticeable. Bumped it down to idle sending pressure to about 15psi or a little less along with a more pronounced knock. ****.

I am leaning away from a water pump or front pulley as the culprit bacause it does not make the noise when cold and not until oil pressure gets too low.

Soundguy, as you suggested, I did take the plug wire off one cylinder at a time but did not really notice a difference. Still had "The Knock".

That's about all the time I had

Also, when replacing the rod and main bearings, I did check with plastigauge, all had about the same reading and appeared to be just fine. Let me clearify here, I used plastiguage with the old AND new bearings and both had about the same readings.

With what I know, I am guessing wrist pin bushings, I did not replace. Is there any way to test if they are to blame?

Trying to avoid the inevitable, but I see myself at least dropping the oil pan real soon.

Thoughts? Thanks

 

[rsallen]

What were the oil clearances? And how do they compare to specs?
You can somewhat feel the wrist pin fit when you have the rod cap off and the crank journal turned away from the rod. But it's only a feel.
A wrist pin wouldn't be high on my list though.

Sometimes you can isolate a noise by using a long screw driver as stethoscope. Hold it like you're going to stab it into the ground and with your thumb on top of the handle fit the knuckle of your thumb into your ear as you move the bladed end around on the block. See if you can isolate where the noise is, it may not tell you what is causing it but it'll give you a location to look for the problem when you tear back into it.

 

[AGRIMAN]

There are a number of things that could be causing your engine knocking and all anyone can do is give you their best guess based on what you have told us.

I have seen everything from a worn pump shaft coupler to a spun bearing to broke crank shaft cause a engine to knock at a idle.

It seems that you are fairly sure the noise is internal. Once you start to tear it down, i wouldn't have my mind fixed on one thing. Go slow and look at everything, check your work from the last time and make sure you didn't assemble something wrong.

 

[Soundguy]

i'd have to agree that a wrist pin knock would be low on my list of guesses.

if it was. it would go away or drop considerably when you de-powered that cyl.

a constant knock is a main journal.

at this poiint I'd drop the cranl and look at the mains. if you find a scuffed one you will know.


ps. can't recall if I saw it or not.. but did you repalce the oil pressure gauge too? if not.. do so.

otherwise the 50 psi cold, 15 hot idle # are 'OK' otherwise.

one thing I would do is look at sleeves.. you might have a loose one. and lastly. insuficient deck/head clearance will knock. and i have seen it only do it hot.

i remove the ehad and gasket and with plugs out lay head on block with 2 bolts just barely in to align it.. and then roll engine over. if head pumpos up and down or rocks. you have clearance issues.

 

[8envy]

Thanks, great advice! I know you don't have much to go on with my descriptions. Maybe I could get a video going... but I'm sure the sound wouldn't be the greatest. Hoping to get to it next weekend when its a bit warmer. I am glad to have attracted your 8Nowledge, you have all been a big help! I will post back with my findings as soon as I have some.

 

[doxford jim]

Before you tear the engine down - have you checked the oil pressure regulator valve and spring ?
I'm not sure what your engine has but a lot of engines have a spring loaded valve near the oil pump, that regulates oil pressure. If the seat is badly scored on has cuts in it, it will give good oil pressure when the oil is cold, but poor pressure when the oil is hot. Also, these valves are often adjustable and usually use thin shims to adjust the pressures.
Might be worth checking out your engine and see what condition the oil regulating vale is in -it won't cost you a penny to look. Might be a simple and cheap fix.
I know when I rebuilt the engine on my JD450 - the oil pressure regulating valve was bad. Replaced the needed parts and I now have oil pressure around 45psi when hot and working hard.
Don't forget that multi-grade oil can make a difference to, over the operating temperature range.
Definitely need further investigation.

 

[Soundguy]

the plunger is under a 15/16 hex plug on front of the engine.

it has a plunger, spring. etc. plunger should have a flat spot.

IMHO. with 50 cold, 20 ish hot. it's not a plunger issue... won't hurt it look if you want to.

 

[8envy]

I did replace both the spring and plunger. The old spring was sketchy looking and the old plunger had slight wear where it butted up against the the seat and I don't mean the flat spot. It did make a bit of a difference but mostly for cold readings. In other words, instead of a reading of 45psi cold, I now get a reading of 50+ psi. I probably only gained 2 or 3 psi for the hot reading but I'll take what I can get. I meant to say this right away if I didn't...

It never occurred to me that the the seat itself could be worn... Hmmm. If it is worn is there an "easy" way to fix it?

 

[doxford jim]

How about adjusting the regulating valve to give say 60psi when cold. It should read a higher pressure when the oil is warm - how much though is the question. Just a thought that a higher oil pressure when warm would be more normal. However, I think the tick or knock you are getting would bother me too.
I can't remember what pressure I got on my old MF675 when the oil was warm - seem to remember around 20psi at 800 rpm or so.
On my old JD450 the oil pressure ran low when at operating temperature and revs around 1000rpm - that was before I rebuilt the engine of course.
On my Jinma the oil pressure is routinely higher even with the engine warm I am getting probably 30psi at around 800rpm.
Anyway, I think you should at least check the regulating valve seat (small mirror and flashlight) and find out what it is like.
Do you have a manual for your tractor? If not you would be well ahead to invest whatever it costs to buy one. I know
you can get reprints from "Yesterdays Antique Tractors" - my guess would be around $75.
Please keep us informed on your progress -" lotsa nosey folk" want to know