2019 L3901 crankcase pressure

ALKubota

New member

Equipment
Kubota L3901
Jun 7, 2021
5
3
3
Alabama
First post!
Hopefully someone has experienced..

I have a 2019 L3901 hst with 88.5 hours on the clock and changed the oil for the second time yesterday. (First owner changed it at 60hrs right before I bought it.) After I ran it for a minute post adding oil i went to check the level after shutting it back off.

When I pulled the dipstick air shot out like I was removing a valve stem core. Obviously a decent amount of crank case pressure.

Today I checked the lines from the catch can and I seem to be getting suction from the intake hose side, and very little pressure from the line that comes from the breather at the top of the valve cover.

Even with the breather side line removed from the catch can I am still getting excessive crank case pressure.. Does the breather on the top of the valve cover limit pressure? Or should it be free flowing? I hooked an old school suction gun to the line and it will collapse the hose and pull very little air with the oil fill cap off. I’ve looked at the parts diagram and don’t see anything standing out that would limit it. Getting to the breather assembly on top of the valve cover will obviously require dpf removal so wanted to check before I dig that deep..

Also noticed a slight bit of oil residue around the split pin drain on the bell housing, and this would explain it pushing oil past the rear main.

Thanks in advance for any help!
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
2,858
314
83
Mid, South, USA
you are addressing the ccv system. Notice I did not say PCV system, although similar they aren't identical.

You will want to refer to your shop manual. There is some maintenance that is supposed to be done with the ccv. Most likely you have a restricted filter but you will certainly want to reference the WSM, if doing it yourself. It's a somewhat complex system.

Early model 3301's had an issue with painting, the factory would put a plug in the valve's aitmospheric vent hole on the valve cover which if left in and the engine was started, the crankcase would build enough pressure to force some oil into the intake manifold, which resulted in a runaway diesel-and usually a plugged or ruined DPF. It was only a few of them, like a couple hundred out of tens of thousands produced, and if yours was built after 2014 it is not affected-but I used it as an illustration to what a plugged ccv system can do on a diesel.
 
  • Like
Reactions: 1 user

ALKubota

New member

Equipment
Kubota L3901
Jun 7, 2021
5
3
3
Alabama
you are addressing the ccv system. Notice I did not say PCV system, although similar they aren't identical.

You will want to refer to your shop manual. There is some maintenance that is supposed to be done with the ccv. Most likely you have a restricted filter but you will certainly want to reference the WSM, if doing it yourself. It's a somewhat complex system.

Early model 3301's had an issue with painting, the factory would put a plug in the valve's aitmospheric vent hole on the valve cover which if left in and the engine was started, the crankcase would build enough pressure to force some oil into the intake manifold, which resulted in a runaway diesel-and usually a plugged or ruined DPF. It was only a few of them, like a couple hundred out of tens of thousands produced, and if yours was built after 2014 it is not affected-but I used it as an illustration to what a plugged ccv system can do on a diesel.
Yep, the CCV system. I removed the hoses from the CCV catch can that drains back to the pan and contains the filter. The restriction seems to be on the side that goes to the breather on top of the valve cover.

I guess the easier question is with the hose off the CCV catch can should pressure flow freely from the open hose that’s connected to the breather on the valve cover? Or is it suppose to be restricted?
Just making sure I’m not missing something easy before I have to deal with the dealer. :)
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
2,858
314
83
Mid, South, USA
It's been coming up on 10 years since I studied the system and I don't want to tell you wrong, so I would suggest looking at the wsm, as it outlined the system's operation pretty well based on memory.

I seem to remember that the valve on the valve cover was sort of a check valve.
 
  • Like
Reactions: 1 user

ALKubota

New member

Equipment
Kubota L3901
Jun 7, 2021
5
3
3
Alabama
Figured it out!

The factory ran the breather side hose through some ridiculously small space and it has it pinched closed. I ran a borescope in from the breather side and found it quick. It’s a welded together bracket and it won’t even wiggle its wedged so tight. I don’t know how they even got it through the slot..

The only option I see is to cut it out and run a new hose. I sent pics to the service mgr to get his opinion first.
 

Attachments

  • Like
Reactions: 1 users

Bark

Member

Equipment
L4701/FM2560LA765/BB2560Case disk Titan P forks
Feb 18, 2020
130
22
18
North CA
That's pretty wild. Kind of surprised the dipstick hadn't wiggled out in the past or that there isn't more gasket seepage.
 

ALKubota

New member

Equipment
Kubota L3901
Jun 7, 2021
5
3
3
Alabama
That's pretty wild. Kind of surprised the dipstick hadn't wiggled out in the past or that there isn't more gasket seepage.
I guess it let just enough squeak by. When you pulled the dipstick it felt like just a couple more psi and it would have shot out.
I’ve found a little residue on the split pin twice but just chalked it up to pressure washing it. Hopefully the rear main will be ok after the fix.
 
  • Like
Reactions: 1 user

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
2,858
314
83
Mid, South, USA
I guess it let just enough squeak by. When you pulled the dipstick it felt like just a couple more psi and it would have shot out.
I’ve found a little residue on the split pin twice but just chalked it up to pressure washing it. Hopefully the rear main will be ok after the fix.
I suggest calling Kubota directly rather than dealing with the dealer. Of course they will direct you to the dealer but the reason I suggest this is because of it being a potential safety issue.

CCV systems HAVE to breathe. If they don't pressure builds up, forces oil to the intake, and at that point if there is sufficient oil in the intake the engine will not turn off. So that means if you are bush hogging and let's say you fall off, the seat switch won't turn the engine off cause it's running on it's own oil, and you get bush hogged. That was exactly the reason that they had a stop sale on the original early L-01's for ccv plug being left in the valve cover vent. If you bring this to attention of the right people, they'll look closely at it. Sometimes the dealers are so busy this time of year that they don't have time to mess with it, so it's "in one ear out the other" for them; rather you go directly to corporate and more likely get stuff done.
 
  • Like
Reactions: 1 users

ALKubota

New member

Equipment
Kubota L3901
Jun 7, 2021
5
3
3
Alabama
I suggest calling Kubota directly rather than dealing with the dealer. Of course they will direct you to the dealer but the reason I suggest this is because of it being a potential safety issue.

CCV systems HAVE to breathe. If they don't pressure builds up, forces oil to the intake, and at that point if there is sufficient oil in the intake the engine will not turn off. So that means if you are bush hogging and let's say you fall off, the seat switch won't turn the engine off cause it's running on it's own oil, and you get bush hogged. That was exactly the reason that they had a stop sale on the original early L-01's for ccv plug being left in the valve cover vent. If you bring this to attention of the right people, they'll look closely at it. Sometimes the dealers are so busy this time of year that they don't have time to mess with it, so it's "in one ear out the other" for them; rather you go directly to corporate and more likely get stuff done.
I sent an email to corporate with my serial # as a heads up. Dealer has been great, they already ordered a new hose for me as I can replace myself in my garage. :) I was a mechanic in a previous life before going back to college so not a big deal at all.