# John Deere 820, 3 cylinder diesel



## Dallas Angele (Aug 13, 2018)

There is a vent tube coming from the top of the valve cover. I am getting a lot of blow back (including oil) through this tube. How serious a problem do I have? Just purchased this tractor on craigslist. I know it is purchased as is. Have run it less than two hours since purchase. I can send a picture if that would be helpful.


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## Guest (Aug 13, 2018)

Hello and welcome to the Tractor Forum. We have some very knowledgeable and experienced members. I encourage you to post add pictures of the problem as best you can. By doing this, your problem will be visible to members. I'm sure one or more of the members will help.

You might consider putting your tractor in the Showcase (located under the TRACTOR button at the top of the page). A perk is that if you add your tractor to the Showcase, it becomes instantly eligible to be entered in our monthly tractor contest, in progress right now. Please be sure to add your vote for September's Tractor of the Month, which is found on the main Forum menu as the fourth category, listed as "Tractor of the month". The poll is at the top of the page. Thank you for your vote, and again, welcome to The Tractor Forum!


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## Guest (Aug 13, 2018)

Blow by from the crankcase IMO would mean very possible blowbby the piston rings or maybe less likely valve seals. Time for some serious diagnostics before jumping to conclusions. I suggest compression checks carefully done.


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## sixbales (May 18, 2011)

The seller should have told you about the blowby issue...… that's part of the "as is" condition. And you should have observed this condition as part of your inspection before buying. How many hours on this tractor?


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## RC Wells (Dec 26, 2008)

While you are eliminating issues, be sure to make sure the radiator is full and cold, start it and look for exhaust bubbles in the neck of the filler. These are quite prone to the head warping and blowing head gaskets, cracking the cylinder liners, and cracking the head. 

These have a cylinder liner type engine, so if you only have compression problems they are relatively inexpensive to replace pistons and liners if you have the tools needed. If a liner has walked in the block they cannot be rebuilt. 

You may want to consider a new short block, less expensive than rebuild labor cost in a shop.


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## thepumpguysc (Jan 25, 2015)

Easiest thing to check, other than the rad. is the engine oil.. is it over filled?
IF SO, the seals in the pump might just be leaking causing the oil to rise.??


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