Checked out a L2500 and it blew off the oil cap, high oil pressure?

[arcteryx]

I went to look at a low hours (187) L2500 Kubota today. While I was driving it around , I heard a loud pop. Turns out the oil cap blew off. The owner and I checked the breather tube and there were not any blockages.

I then drove it for another 5 minutes. It did not blow off, but I did remove the cap after I came to a stop. It had a lot of pressure that came out. The owner took the valve cover off. There was nothing blocking the tube or the breather outlet. There does seem to be some air coming out of the breather tube, but not a lot.

I took a video of this as well as pics. In the video, I started the tractor and clicked record. So it was on for maybe 30 seconds in the video. You can see the air as well as hear the pressure when I remove the cap. I also started the tractor for 5 seconds and checked the cap, with the same results.

Is this normal? Or is this excess blow by? What other things could cause this? I am not sure wher else a blockage could be. I really like the tractor, but I need to know that it is mechanically sound as well as I can run the tractor more than 5 minutes without the cap blowing off.

Pics/video Kubota L2500 - a set on Flickr

Thanks in advance.

 

[PoorPlowboy]

Sounds like a cracked engine block or cylinder head allowing combustion pressures into the crankcase to me.

 

[kuboman]

Now that is just weird:confused2: Unless there is a complete blockage between the crankcase and the head it makes no sense as to why the cc pressures up like that.:confused2::confused2:

Are you sure the breather tube is not blocked.

 

[kuboman]

Let me re-phrase. You should not be getting pressure at the filler cap. Run it with the valve cover off and see if it acts the same. Whether you have a cracked block piston on anything else you should NOT be getting pressure at the cap unless something is blocked. From what I saw on your video there is not excessive blowby, the problem is it is not being vented.

 

[jmanatee2]

Your crankcase vent is not working... There is no way to build pressure under the cap if the vent is working.

Maybe a mud dauber or something made a nest.

 

[arcteryx]

Thanks for the reply. We took the valve cover off and the same thing happened.

Where is the crankcase vent on these?

 

[jmanatee2]

Very odd head should have a drain to pan to let oil drain back, I thought air can flow freely too

 

[kuboman]

Thanks for the reply. We took the valve cover off and the same thing happened.

Where is the crankcase vent on these?

The same place the oil that lubricates the valve train goes. The top end oil drains down through several ports in the head and into the block. If the oil is draining away then the crank case should be venting too.

 

[leonz]

If its anything like the old two cylinder Kubotas the vent will be by the left side of the flywheel in the front of the motor which is the right side of the tractor.

The usually they have a permanent screen in them to keep the pests out, at least I believe the Duetz air diesels did anyway from what I remember.


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[art]

The vent tube comes off the top of the valve cover and comes down the side of the block. It is in your pic's and it looked clean on the top but from time to time they get filled in the bottom.