850 pushrod problem

   / 850 pushrod problem #1  
A

AA7TU

Member
Joined
Aug 17, 2017
Messages
28
Location
Clallam Bay, WA
Tractor
Ford 850
My 850 started running very poorly. I found no compression in cylinder 4. Taking off the valve cover, I noticed that the intake valve pushrod end was not properly seated on the rocker arm, and was hung up just pushing on the outer edge of the depression. The valve still went up and down as I turned the engine, but because the pushrod wasn't seated all the way, the intake valve did not close. I was able to snap the rod back into the seat on the rocker by hand. That allowed the valve to operate normally, and compression was restored.

My questions are how could this happen? What do I need to look at further to see what is going on? Do I need to take off the head? I am not able to find an exploded diagram of the engine online. There was one that I had bookmarked, but it seems that website has now changed and it's gone. I am not a very experienced engine mechanic, but I keep my stuff running. This is my first encounter with the innerds of this particular engine. Thanks for any advice.
 
   / 850 pushrod problem #2  
I can think of a couple of things that could cause it but best bet is you have a sticky valve. I would pop the valve cover and verify the valve clearance is correct and give it a good cleaning.
 

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   / 850 pushrod problem
  • Thread Starter
#3  
OK. thanks for that. I went through and checked the clearances. Some were a bit loose, but the one on number 4 intake was rather too tight, as in no clearance. That would perhaps also correlate with being sticky as well. So they are all adjusted and working as far as appearances go.

I will do some more research. Is there a good procedure for sticky valves that does not require disassembly? Some additive that actually works, even though they all say that they work? I can imagine that there is a carbon buildup, as I had some funky fuel in there, unfortunately.
 
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   / 850 pushrod problem #4  
A good healthy dose of Seafoam could clean up some carbon or Techron both are cheap enough. I personally use MMO added to all my gas cans, a small dose of 4 oz. per gas can helps the gas stay fresh and it also cleans. I have had zero problems with the blended gas getting funky since I started doing this.
 
   / 850 pushrod problem
  • Thread Starter
#5  
Very good. Thanks for the help. I will try these and report back. It is soon time to get out and about with the tractor again, so I am glad of an easy solution.
 
   / 850 pushrod problem
  • Thread Starter
#6  
Today I checked the valve clearances and ran the engine with some Seafoam in both fuel and oil. Got a bit of white smoke out, not much. The engine is back to good smooth running. Checked the clearances again and they were all stable, so it seems the problem was just specific to the number 4 intake. I am sure that once the engine gets up to working temperature in warmer and dryer weather things will clean out a bit more.

I appreciate this forum very much. It has always come through for me.
 
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