What happens if you use thicker hydraulic oil?

[catmanjan]

Hello I have a 1976 cherry picker with a hydrostatic drive

The fluid that was in there was no good, full of water - not surprising as it had been sitting in a paddock for a decade

I drained it and put in ISO64 (that was what I had) but the performance has been poor. The boom is slow to lift and the wheels move with very little power

I later noticed on the nameplate it calls for "Terasso 43" hydraulic oil, which I understand is equivalent to modern ISO32

Do you think me swapping to ISO32 would help the performance problems I am experiencing?

Thanks for your time.

 

[oldnslo]

Thinner oil will only help if the pump is cavitating (starving for oil). Indicators of cavitation are noisy pump under load, system jerky, oil gets aerated and foamy looking.

Did you clean any inlet screen and replace the filters?

 

[5030]

Considering it was loaded with contaminated fluid, probably not. Sounds to me like you have internal issues You can try changing to a lighter grade, nothing to lose compared to rebuilding the pumps.

 

[catmanjan]

Hello oldnslo,

Hard to tell if the pump is noisy as the engine is so loud, however the boom is jerky when lifting and the oil does develop a foam on the surface - there was a suction filter which I have removed entirely as part of this diagnosis.

Hello 5030,

Thanks for that - I will look into getting some ISO32, unfortunately it takes at least 100L so while it is cheaper than getting the pump rebuilt it is not without cost. I am not entirely sure getting the pump rebuilt is even an option, it is an Afron power ladder which were made in Israel and the only numbers on the pump are 72-108 (not sure if that is a model number) but I doubt they exist any more!

 

[5030]

I know all about bulk fluid, I buy my hydraulic fluid in 55 gallon drums. Each of my tractors take 15 US gallons a change, lets see, that is 60 quarts per and a liter is less than a quart (I think) so I use quite a bit myself and that don't count the gear oil for the drives either.

One thing about hydraulic fluid and that is, so long as it don't get contaminated, it lasts quite a while. I change mine every 2 years and all the filters as well because I'm using the tractors for ag purposes.

Even if your pump is obsolete, I'm sure any competent machine shop can rebuild it. Pumps are pumps.

 

[Bob Rooks]

Your "Terasso 43" hydraulic oil" equates to ISO 46 hydraulic oil. And fwiw, I have been using a multi-grade ISO AW 32/46/68 hydraulic oil in all my equipment for years. It's great for the varying temperature conditions, and saves on inventory. I couldn't be more pleased with it.
If you are having problems with slow movement that indicates you could have a restriction in the system - make sure your valve stack lines up correctly. If you are having problems with power that indicates a pressure problem, could be a bad pump or a sticking relief or spool valve. I would install a pressure gauge to see exactly what your pump output is.

 

[catmanjan]

Your "Terasso 43" hydraulic oil" equates to ISO 46 hydraulic oil. And fwiw, I have been using a multi-grade ISO AW 32/46/68 hydraulic oil in all my equipment for years. It's great for the varying temperature conditions, and saves on inventory. I couldn't be more pleased with it.
If you are having problems with slow movement that indicates you could have a restriction in the system - make sure your valve stack lines up correctly. If you are having problems with power that indicates a pressure problem, could be a bad pump or a sticking relief or spool valve. I would install a pressure gauge to see exactly what your pump output is.

Hi Bob, apologies as I am only now becoming more familiar with hydraulics - how do I check my valve stack lines up correctly?

 

[Bob Rooks]

Hi Bob, apologies as I am only now becoming more familiar with hydraulics - how do I check my valve stack lines up correctly?

That's a term I use to describe when all the valve spools are in the "neutral" position. A sticking spool or linkage will not allow the spring to return to the neutral detent and partially block a port. If you have sloppy linkage you may not detect it easily (possibly a broken spring too, this happens). I don't know if you have a closed or open loop system, or how many spools (functions) in your valve stack. Do you have a pic of your machine?

 

[oldnslo]

Catman
If the pump, valve assembly, drive motors are accessible a simple check than you can do is check for heat rise or hot spots while operating a function. With a function activated, check the pump housing to see if heats up significantly quicker that the inlet and outlet lines.

Check the tank line from the valve stack to see if it is hotter than inlet.

If safe check drive motors to see if they get hot.

You may have to keep the function activated for 2 - 3 minutes to verify heat rise location.

Reason for this is that in hydraulics inefficiency creates heat and fluid bypass in the pump, across a motor or across something in the valve stack will create heat and help point you towards a possible cause.

 

[catmanjan]

I hate finding forum posts that don't have a conclusion so just to let everyone know what happened.

I ended up removing the suction strainer which was covered in gunk - I opted to not replace it, the machine is ancient and hopefully by the time the hydraulic pump dies I will be in a position to replace it with a fully electric system (there is a blog post of someone doing this with the 1975 model here: Convert 1975 Afron Cherrypicker? - AEVA Forums)

In the end all I had to do was replace the drive belts, the belt I had on it was too loose - it was a 37" and I ended up using a 35" and it works just fine now, there must have been a lot of slipping occuring, I only noticed how loose it was recently when I was able to see how fast the pulley turning the hydraulic pump was moving by eye, whereas now it is moving so fast that the pulley is a blur!

Thanks for all of your suggestions, hopefully this thread is of value to someone in the future.