Hydraulic oil change interval

[Columbo]

Hi all- so I am planning the pre-season maintenance on my Cat 311B, s/n 8HR00401 (crossover s/n 8GR00401). I had the hydraulic oil sampled before I purchased it and again after 100 hrs. Machine now shows 6050hrs. The oil level sensor for the hydraulic oil failed at the end of last year, seems like this would be a good time to drain the tank and refill with fresh oil. Given the oil sample history (although limited) is there a need to flush the system more completely?

I do not know what type of oil is in the hydraulic system currently. I was planning on using 10w TO4 oil (Shell Spirax) for the drain and fill? Machine operates from 20-85 degrees F ambient temperature.

Is there anything I am missing here or something else I should do for preventative maintenance as well (besides all new filters)? I will also inspect and clean any screen/filter in the tank.

 

[Nige]

The oil level sensor for the hydraulic oil failed at the end of last year, seems like this would be a good time to drain the tank and refill with fresh oil. Given the oil sample history (although limited) is there a need to flush the system more completely?

TBH if you wanted to drain the existing oil from the tank into clean containers, fix the oil level sensor, then put the same oil back again - you could.

It's clean (ISO better than the spec for new/fill oil), there is amost no dirt present, and very low numbers of wear metals. If it was mine that same oil would be going back into the tank again. YMMV.

At this point in time with so few hours since the existing filters were installed even new filters could be considered "optional", although I would definitely remove/inspect/clean the screen(s) in the tank while you have it drained.

 

[Columbo]

Thanks, Nige! I was hoping you’d weigh in. I know that you’re very careful on the maintenance so if this oil is still useable for you I’m certain it will be fine for me as this is just a personal use machine. I’ll carefully drain it, make the repairs and return it to the tank. Then I’ll keep periodically monitoring it with samples.

 

[Coaldust]

What Nige said.

I certainly would not change it. The new oil will probably be more contaminated than your existing oil that has been cycled through a filter multiple times. Oxidation and contamination is what kills hyd oil.

Take care to keep the drained oil clean.

 

[Columbo]

@Nige or @ahart could you (or someone else) please post the removal/cleaning/reinstall process for the in-tank hydraulic strainer filter? It looks like I should buy new o rings for the cap? S/N 8GR00401

Thank you!

 

[ahart]

Attached

 

[Columbo]

Thank you @ahart! I’ll be making a parts run later this week.