Recently my Deere John has a loud tap that seems to be coming from the top side of the motor, no blow by, 8000 hrs on the machine, is there any quick way to check the valves without taking the heads off?
Take the valve cover off. Turn it over by hand or run it with the valve cover off. You should be able to see the valves moving. You might have a bent push rod or bent valve.
Could be a wrist pin also. Dunno about your machine, but out here in the Northwest many of the 890E's had head gasket problems, are you seeing any bubbles in the coolant or odd color/smell exhaust? They cleared it up after a couple years, was actually a head bolt engineering problem.
8000 hrs. Has it ever had an overhead? My guess is you'll have an intake valve that has about 0.100 gap. If all the rockers are fairly close, you're going to have to do major surgery. Good luck.
I'm hoping its more like a bent push rod, just no more than above idle since the noise started, I was trying to make it last this season then do a complete overhaul, been well serviced. Thanks for the replies also, I will keep you updated.
The odds of a push rod bending due to metal fatigue are pretty long... other than that I would have to wonder what would bend the push rod? Could be a flat cam lobe which would cause excessive valve lash, or possibly even a leaky injector. First time I ran across an injector that was dribbling fuel before it was supposed to snap open, I would have swore it was a rod knocking. Scared me because I had just assembled the little Perkins 4-banger and I can tell you my heart sank when we lit it off the first time and it was knocking!
Second that on the leaky injector. Why'd you have to throw us off with the valve question??? Have you tried loosening injector lines one at a time to see if the noise goes away? (assuming you have injector lines)
I will try that 1st, an older mechanic told me it sounds like a injector, but I shrugged off the idea. That would be a very good deal to replace an injector... or even cam shaft.