Bobcat S300 Oil Pressure Issue

[05sprcrw]

I am fighting a small issue with the bobcat s300, and suspect its either my o ring on the pickup tube or the pickup tube itself. However before I go through the work of pulling the motor I thought I would check with others and see if anyone has had this issue.

The motor was overhauled within 50 hrs of this, its just now getting warm enough that the oil can get a bit thinner and I am using it longer stretches. It will run for about 1 1/2 - 2 hrs with pretty stable oil pressure of around 50-55 psi around 1800-2000 rpm when the oil is warm and will make 65-70 psi on a cold start up at idle before upping the speed. After that approx 2 hrs or a little faster if I am on mainly uneven terrain it will start to drop off slowly, until it starts to get around the 25-30 psi at approx 1800-2000 rpm before I get nervous and shut down. If I come back after a while of it sitting anywhere from a a couple of hours to over night it will start back up and have good pressure. Usually after I shut it down I am on to another project and don't need to get right back in it. So I don't have an idea if its temp related or something else.

Things I have done:
Changed oil 15w40
Changed oil filter
Changed the sender/sensor
Changed the oil pressure relief valve and spring

I picked up a mechanical gauge and will install that tonight to try and verify if my sensor and the mechanical gauge match to make sure a wire or something isn't the issue.

At this point I don't suspect the bearings have had any issues, only two things I can think are a little over filled on oil (upper limit on the dip stick but not over), or the pickup tube has a leak and air is getting in the oil. When I pull the dip stick there will be a few bubbles on it causing me to think air is getting in the oil. It doesn't come out covered in bubbles only about 3-8 bubbles (guessing but you get the idea).

Any help/suggestions would be appreciated.

 

[Vetech63]

Definitely check the oil pressure with an accurate mechanical gauge before you do anything else. Come back and report your findings.

 

[Bls repair]

^^^^^^^x2

 

[05sprcrw]

I put a mechanical gauge on it last night at start up idle was 66 psi from the sender, and about 63-66 psi on the mechanical gauge (hard to view, funny angle). I let it run for approx 30 min got it up to operating temp(179 deg), at idle the oil pressure was 56 psi from the sender, and the gauge was showing about 54-57 psi. Its been raining and will be for several days now I won't be able to work it for an extended period of time, but currently I feel like the sender is probably good.

 

[DIYDAVE]

Kubota motor? I had an older, much smaller Kubota, that had the oil pickup o-ring harden up, and crack. It had the same symptoms, idiot light would start to blink on, as the motor got warmer...

 

[05sprcrw]

Thanks DIYDAVE, that is what I am suspecting, but when I overhauled the motor I put a new o ring in. Only thing I can think is either a the pickup had a crack in it I didn't see, or more likely I must have pinched the o ring when I put it back together.