Hydraulic power fading with normal use.

[nox273]

Hello all.

I have an older model Dingo type skid steer mini loader that I am having some issues with around losing power with prolonged use.
When I first start and use the loader the bucket lifts well and crowds equally as well, it drives forward and backwards, skids to the left and right pretty good.
The problem starts when I have been using the loader for any longer than 1/2 an hour the hydraulic performance starts to drop off to the point where the loader finds it difficult to skid steer at all.
Both lift cylinders and crowd cylinder appear to function well. The loader will still drive forwards and backwards although slightly slow than when cold but doesn't seem to have the same grunt as when it was cold.
This comes quite annoying as the oil becomes quite hot (50C - 60C) and takes sometime to cool down. Here are some details of my machine.

Motor - Honda GX390 - 13hp - 3500rpm (44 hours old) - (yes a little under powered)
Pump Casappra - 9cc (Group Din 2) - (44 hours old)
Crowd cylinder is a single 2" ram
Lift cylinders are 2 x 2' rams
4 x Vickers branded CR18 wheel motors - 285cc - 180rpm (new seal kits in all motors 15 hours)
Oil capacity approx 43 litres (new oil only 30 hours old) - Fuchs Renolin B 68
Reconditioned valve block (approx 60 hours)
System pressure ? - Waiting on pressure gauge to arrive.

Any body have some ideas on where I should start looking. Any help would be muck appreciated.

 

[hayden]

Has it just started doing this, or has it been doing it all along?

Your pressure gauge is the right starting point to figure it out. Start with the main system pressure and see if it drops off as the oil heats up. If it does, then it's probably the system relief valve or the main pump. If the main pressure remains high, then check the pressure in the drive motor circuits. If those are dropping off then it's either the control valve or the motors themselves. It would probably be worth checking both motor circuits to see if they behave the same or differently.

 

[jenkinsph]

hayden offers some good suggestions ^^^^^

How many hours on the Dingo? Might be excessive wear on the wheel motor(s). It would be helpful to know if it heats up while stationary, not using the wheel motors and raising and lowering a full loader bucket.

 

[nox273]

Has it just started doing this, or has it been doing it all along?

Your pressure gauge is the right starting point to figure it out. Start with the main system pressure and see if it drops off as the oil heats up. If it does, then it's probably the system relief valve or the main pump. If the main pressure remains high, then check the pressure in the drive motor circuits. If those are dropping off then it's either the control valve or the motors themselves. It would probably be worth checking both motor circuits to see if they behave the same or differently.

It has done this all the time I have owned it. The previous owner put in the new pump and motor and rebuilt the valve block.
I changed the oil even though the old oil looked nice and clean. I also had the new seal kits put in all motors by a hydraulic shop and the mechanic said the motor while a number of years old were in very good condition and showed very little signs of wear.

 

[nox273]

hayden offers some good suggestions ^^^^^

How many hours on the Dingo? Might be excessive wear on the wheel motor(s). It would be helpful to know if it heats up while stationary, not using the wheel motors and raising and lowering a full loader bucket.

Not sure how old the machine is, late 90's I reckon. I would have to check if it heats up as quick when stationary.

I was thinking does the pump supply enough flow once warm to drive all 4 motors.

 

[IceStationZebra]

I couldn't find the motors online, but 50-60c (122-140f) seems on the cold side for vg68. I would expect vg32 at those temps. The thicker oil could be masking some wear or leakage until you get it to that temp.

As it gets hotter and you lose performance, does the engine seem to work harder or easier?

ISZ

 

[nox273]

I couldn't find the motors online, but 50-60c (122-140f) seems on the cold side for vg68. I would expect vg32 at those temps. The thicker oil could be masking some wear or leakage until you get it to that temp.

As it gets hotter and you lose performance, does the engine seem to work harder or easier?

ISZ

The engine seems to bog a little less when hot than it does when cold. Not a huge difference but noticeable.
I have also noticed when all is hot and you are trying to skid steer not all wheels rotate at the same speed and appear notchy in there movement a bit like clockwork as if there is not enough fluid to drive all 4 motors at the same time at the same speed. When cold they are much smoother.

Hopefully my pressure gauge will arrive in a couple of days and I will be able to narrow it down with some gracious help of the forum.

 

[nox273]

I couldn't find the motors online, but 50-60c (122-140f) seems on the cold side for vg68. I would expect vg32 at those temps. The thicker oil could be masking some wear or leakage until you get it to that temp.

As it gets hotter and you lose performance, does the engine seem to work harder or easier?

ISZ

What temperature would be considered normal operating temperature for 68 weight oil.

 

[nox273]

I couldn't find the motors online, but 50-60c (122-140f) seems on the cold side for vg68. I would expect vg32 at those temps. The thicker oil could be masking some wear or leakage until you get it to that temp.

As it gets hotter and you lose performance, does the engine seem to work harder or easier?

ISZ

Link to motor below. Model is CR18

Products | TOKYO KEIKI U.S.A., INC.

 

[CJONE]

Pump is more than likely worn. Need to do a test with a flow/pressure meter. The hotter the oil gets the more a pump will slip and create more heat. Vicious circle. 95% of the time with these symptom the pump is the problem. Not a fan of Cassapa pumps. CJ

 

[wdchyd]

Pump is more than likely worn. Need to do a test with a flow/pressure meter. The hotter the oil gets the more a pump will slip and create more heat. Vicious circle. 95% of the time with these symptom the pump is the problem. Not a fan of Cassapa pumps. CJ

X2..........yep, time for a flow test

 

[IceStationZebra]

What temperature would be considered normal operating temperature for 68 weight oil.

I couldn't find any specific data from Keiki so I looked at general recommendations. You want to look at two things - viscosity and oxidation.

Viscosity: generic optimum range is 10-50 cst. For the common viscosities we get:
VG68 - 45-92c (113-198f)
VG46 - 38-84c (100-183f)
VG32 - 30-75c (86-167f)

Oxidation: higher temps oxidize the oil faster, in fact every 10c (18f) doubles the rate. For nonsynthetic oil the tempuratures are generally recognized as:
recommended: 49-60c (120-140f)
max: 82c (180f) [~2500hr life]
do not exceed: 93c (200f)

So your normal temps of 50-60c are a little on the cool side of the range but certainly acceptable. Most mobile equipment pushes the high side because it minimizes cooler size, a little lower pressure drops, etc.

I stand corrected, ISZ.

 

[nox273]

I thank everyone for their time and comments.

Today I received my pressure test gauge (don't have the money for a flow test gauge). I connected it too my auxiliary port and ran the motor from cold. pressure was 2050psi with the motor at maximum revs (3500 rpm).
I then ran the digger for a good half an hour with a good combination of using all controls and making the digger labour with many heavy loads until I noticed the power dropping off.
I then stopped the motor re-connected the pressure gauge and took the reading again. It quickly jumped to 1500psi and slowly crept to 1600 psi over a few seconds and would not go any further.
I then backed out the pressure relief valve which is mounted right next to the motor until I had a reading of 1000psi. Then I screwed the relief valve in half a turn at a time and checking the gauge. It slowly went higher as I screwed it in until it hit the 1600psi mark and the pressure would go no further no matter how far I adjusted the RV in. It even bottomed out at one point but the reading was still 1600psi.

The next test I would like to do is adjust the RV when it is cold to see If I can get any more than 2000psi. Not sure if it will as the motor starts to bog down quite considerably at 2050psi when cold.

Is it starting to look like the pump, seems to be heading that way.

 

[jenkinsph]

Sounds like that new pump with low hours is not working out. Is it under any warranty?