Cat 930G Hyd Pump noise

[Diagonal Brace]

Went to try out one of these loaders and the hyd pump seemed to be moaning/groaning excessively. Does anyone have any suggestions what this may be. Something simple perhaps. I looked up the parts manual online and it has a piston type pump. Thanks.

 

[Spanrz]

Went to try out one of these loaders and the hyd pump seemed to be moaning/groaning excessively. Does anyone have any suggestions what this may be. Something simple perhaps. I looked up the parts manual online and it has a piston type pump. Thanks.

Check pressures? Open Filters? Check the little valve that controls the piston pump (pressure flow compensator).

Pump cavitating? (sounds like pumping marbles)

How many hours on the machine?

 

[Diagonal Brace]

At Cats suggestion we pressurized the hyd tank and the noise stopped. We are checking the suction connections at present. What else can cause cavitation? What does the pressure flow compensator do? Thanks.

 

[cpfrank]

Other reasons for cavitation are worn pump, worn charge pump or hardened internal seals in the pump due to overheating. Flow comp. valve limits flow to implements if more than one are needed.

 

[WhyWhyZed]

If the suction line is letting air in, the pump noise is technically Aeration, not Cavitation.

Cavitation happens when the pump suction is restricted. During Cavitation, the pump sucks so hard on the restricted line, it actually BOILS the oil. (A Fluid pulled into a high vacuum will boil without heat). The vacuum bubbles then IMplode violently as they go through the pump causing cavitation erosion.

Aeration is similar in damaging effects to a pump, but with aeration, the bubbles are actually bubbles of air being drawn in the suction line due to leaks. The air bubbles EXplode as they go through the pump causing almost identical damage as cavitation.

Both are noisy and destructive to the pump.

The Pressure Compensator is a valve that "destrokes" a variable displacement piston pump when the system pressure reaches a defined maximum pressure setting. 3750 psi on your loader. This is more efficient than a relief valve because it reduces flow and unloads the engine, thus saving fuel and heat generation.

The Flow Compensator is another valve (Part of the same "chunk" as the Pressure Comp) which Upstrokes the pump based on demand. A load sensing signal sent through a small hose from the directional control valve signals the pump as to pressure demands of the system. The Flow compensator upstrokes the pump until the pressure at the outlet of the pump is a few hundred psi higher than what is required at the highest pressure point in any hydraulic cylinder on the machine. (405 psi higher on the 930G).
For example, if you curl the bucket and the load dictates that it requires 1400 psi to do so, the pump will increase it's output flow (regardless of engine rpm) until the pressure supplying the control valve is 1805 psi. This difference of 405 is what Cat calls margin pressure. The higher the margin, the jerkier the hydraulics. The lower the margin the more lethargic the system becomes.
This flow compensation or flow on demand design is what defines the hydraulic system as "Load Sensing".

 

[FFR1998]

Very useful information! I'm definitely glad I found this site. We are having problems with our loader and am hoping to get some answers. Thanks for the post and info =)

 

[TQScott]

If pressurizing the tank helped, I would check the breather filter element. There is a hose that leaves the tank on the left side of the machine and heads down into the frame. If it can't breathe it will groan. The filter looks like an inline gas element...steel housing spliced into the hose.

 

[Chris91786]

If pressurizing the tank helped, I would check the breather filter element. There is a hose that leaves the tank on the left side of the machine and heads down into the frame. If it can't breathe it will groan. The filter looks like an inline gas element...steel housing spliced into the hose.

A lil late bud :drinkup

 

[cps]

If the suction line is letting air in, the pump noise is technically Aeration, not Cavitation.

Cavitation happens when the pump suction is restricted. During Cavitation, the pump sucks so hard on the restricted line, it actually BOILS the oil. (A Fluid pulled into a high vacuum will boil without heat). The vacuum bubbles then IMplode violently as they go through the pump causing cavitation erosion.

Aeration is similar in damaging effects to a pump, but with aeration, the bubbles are actually bubbles of air being drawn in the suction line due to leaks. The air bubbles EXplode as they go through the pump causing almost identical damage as cavitation.

Both are noisy and destructive to the pump.

The Pressure Compensator is a valve that "destrokes" a variable displacement piston pump when the system pressure reaches a defined maximum pressure setting. 3750 psi on your loader. This is more efficient than a relief valve because it reduces flow and unloads the engine, thus saving fuel and heat generation.

The Flow Compensator is another valve (Part of the same "chunk" as the Pressure Comp) which Upstrokes the pump based on demand. A load sensing signal sent through a small hose from the directional control valve signals the pump as to pressure demands of the system. The Flow compensator upstrokes the pump until the pressure at the outlet of the pump is a few hundred psi higher than what is required at the highest pressure point in any hydraulic cylinder on the machine. (405 psi higher on the 930G).
For example, if you curl the bucket and the load dictates that it requires 1400 psi to do so, the pump will increase it's output flow (regardless of engine rpm) until the pressure supplying the control valve is 1805 psi. This difference of 405 is what Cat calls margin pressure. The higher the margin, the jerkier the hydraulics. The lower the margin the more lethargic the system becomes.
This flow compensation or flow on demand design is what defines the hydraulic system as "Load Sensing".

Just to let you know, Il be picking you brains sometime WhyWhyzed:drinkup

 

[gravelpete]

I have a 928GZ that has had a noisey pump since day 1, If you turn the loader and curle the bucket at the same time it groans. Cat claims the pump is not covered on extended warranty, this issue was brought up to them in the beginning but they never really figured it was an issue, now it seems to be getting worse.

 

[WhyWhyZed]

sounds like it would be a good idea to get someone to look at it.
I'd start with cutting the hydraulic filter to inspect the pleats, and send in an oil sample.
Pump is not usually covered by an ext powertrain warranty.

 

[gravelpete]

We have taken an oil sample and have sent it in and are waiting on the results.

 

[gravelpete]

I would have thought the hyd. pump would be under extended warranty as the machine could not be moved with out the pump. I know it would run but you would not be able to steer it. I am starting to lean towards other manufactures other than Cat because they don't seem to stand behind there product as well as some others.

 

[WhyWhyZed]

I don't think any of the brands cover the imp or steer pump in ext powertrain warr., but regardless... hydraulic pumps wouldn't top my list of possible causes yet.

Depends on the noise and the area it's coming from, but I'd start by looking for loose or improperly clamped tubelines, hoses rubbing, etc., especially with problems there "from day 1" .

And the oil sample is a good step, but not as telling as cutting a filter.

Turning and curl the bucket makes noise?... Why not turning and lifting? Turning and dumping?
That's why I wouldn't suspect the pump.
there's 2 pumps - 1 for steering and 1 for implements
the implement pump doesn't know that you are curling the bucket as opposed to raising the loader frame so the pump theory not computing for me..

Tossing in a bottle of 1U9891 Caterpillar Hydraulic Oil Additive never hurts....

 

[gravelpete]

It makes the noise turning and lifting as well but not turning and dumping that I have noticed. I did not realize it has 2 pumps on this machine, that isn't the cas on all machines is it? I replaced the pump on my 950F and never seen 2 pumps.Once in a while when you are really working the bucket in the bank you can hear the pump as well. Thanks for the help.

 

[John C.]

I've been around a number of these machines and found them to be noisy all the time. As I recall, there is a hydraulic driven fan and a seperate pump for that which makes lots of noise.

The proper questions to ask are;

(1) Is there a perfomance issue with the machine? The machine won't steer, the brakes don't work properly, ride control drops the bucket when it engages or the engine cooling fan isn't turning fast enough to keep the engine cool. Checking cycle times and pressures must be done before any speculation is done on which component is making noise.

(2) What are the circumstances of operation of the machine? Different operator, climate change, recent maintenance or lack thereof, recent repair, different material being handled and so on. Maybe the operator just noticed it because he is now running with the door closed for cold weather.

I've spent a lot of customer money chasing gremlins that existed in an operator's mind for whatever reason. A tangible affect that can be verified has to be established to justify stopping production and possibly sending people home without a paycheck.

Good Luck!

 

[WhyWhyZed]

hydraulic driven fan and a seperate pump for that which makes lots of noise.

that's right, there's a 3rd pump as well, a small gear pump that runs the brakes and fan.

pumps:
1. Main Implement - Vane type fixed displacement
2. Steering - Load Sensing Variable displacement piston pump
3. Brakes and Fan - Gear type fixed displacement

 

[Diagonal Brace]

Is the 928g different than the 930g? Because the 930g uses a piston type pump for the implements and steering.

 

[WhyWhyZed]

yes the two machines are quite different. Tacking all this 928G stuff on this thread was bad etiquette.

 

[Diagonal Brace]

Thanks for the clarification WhyWhyZed. You sure know these machines. Over in the Tractor Loader Backhoe section is another person having problems with a 930G. You can probably help them.