Test hydraulic gear pump

[flyMt1962]

My hydraulics on my Mitsubishi MT3201FD are weak. I’ve checked the usual suspects and they all seem fine. Is it possible to test the pump before I spring for a new one?

 

[oldnslo]

Yes pumps can be performance tested. Typically you need a method to measure flow vs pressure.

A very simple quick check is if your pump is exposed so that you can see or touch it is to check temperature of housing vs inlet while under load. If housing heats up quickly that indicates pump is leaking internally.

The test stand method Example:
Your pump may produce 5 GPM at 200 PSI but only 2 GPM at 2000 PSI. This would indicate a pump that is worn out.

 

[Tinhack]

Is it possible to test the pump before I spring for a new one?

As OldnSlo says, yes but the test equipment may cost more than the pump.

 

[flyMt1962]

Thanks the pump is exposed. I’ll give it a feel test.

 

[rScotty]

My hydraulics on my Mitsubishi MT3201FD are weak. I’ve checked the usual suspects and they all seem fine. Is it possible to test the pump before I spring for a new one?

Yes, it's possible and not too difficult. At the minimum it would take screwing together some commercially available gauges and parts. All pumps are rated at how much flow they put out at a certain pressure. More pressure, less flow rate.
As pumps age, the max pressure they can create declines faster than the flow rate.

Finding your tractor's system pressure is easy and cheap...you can do that for $50 to $150. That will also enable you to set the total system pressure via the main system relief valve...which is sometimes all that is necessary.
Finding out if the pump can reach even reach the required system pressure tells you if you gain anything by replacing it.

Measuring flow rate as well at differing pressures is more difficult/expensive. Usually knowing the pressure is enough

Do you have some specs on your current pump? It would be nice to know what size pump you are dealing with.
rScotty

 

[Fxfymn413]

Before you jump on the most serious problem you can think of i.e. the pump, do a lot of troubleshooting. Its human nature to jump to the most serious thing that can go wrong first, but it rarely is.

If you have access to the service manual follow their test procedures.

Test pressure gauges are readily available at a reasonable cost that can be plugged into a coupler. Find the specs for your machine and compare them to your results.

You will not be measuring flow, but if the pressure is within specs it tells you that flow could be an issue.

I would also disconnect as much of the system as your couplers allow just ensure an internal leak is not the issue.

 

[flyMt1962]

Thanks for the advice. I’ll test the pressure before I take the plunge. The manuals I’ve been able to find are for models close but not exactly mine. I’ll buy them and green what I can from them. Thanks again

 

[rScotty]

Thanks for the advice. I’ll test the pressure before I take the plunge. The manuals I’ve been able to find are for models close but not exactly mine. I’ll buy them and green what I can from them. Thanks again

Yes. Books help. A lot of times there will be a port somewhere for testing the pump pressure. Then finding out more about your hydraulic power is as easy as replacing a pipe plug with a 5000 psi glycerin-damped pressure gauge - about $20 at Ace Hardware. The gauge can stay installed permanently if you wish.

A hydraulic pump is theoretically capable of very high pressures, but in compact tractors it is limited by a relief valve so that it never exceeds 3000 psi - and often they work around 2400 psi. The exact number is not critical. Plus/minus 10% is common.

So....the simplest test is to use a T fitting to insert a gauge where it can sense pressure in a line. Thenload the hydraulics by trying to lift something impossible while watching the gauge to see what max pressure the relief valve allows. If the max pressure is too low, then we first suspect the relief valve - which are always adjustable/cleanable/replaceable. Also they are much cheaper than pumps. A failed or stuck relief valve is just as common as a weak hydraulic pump.... maybe more so.

If the pump is capable of developing enough pressure to trigger the system relief valve at a reasonably high pressure, then replacig the pump will not do anything for you. In that case it is time to look elsewhere for the weakness problem. That is why measuring and setting the max sysem pressure comes first.

To do this, step #1 is finding a place to insert a gauge. Do you have a front end loader or any place with a quick disconnect for the hydraulics??

Often a popular gauge place on tractors that have a loader is to use a "Hydraulic T fitting" to put the gauge where it can sense the pressure where the hydraulic pump pressure connects to the loader control valves. Often there is an "IN" cast into the loader control valve at that proper port. With a hydraulic T installed, the gauge can just live there if you want. Total cost of a gauge and special high pressure T fitting is way under $50 and it will monitor your hydraulic performance forever.
good luck,
rScotty

 

[Xfaxman]

Is it possible to test the pump before I spring for a new one?

Yes, and do the adjustment to increase the pressure.

 

[jonsstihl]

I just went through this with my tractor. I have had a weak pump since I got it around 500 hours. I had the dealer adjust the pressure when they installed the third function and they said adding shims to the relief valve did nothing past 2400 psi. spec is around 2600psi for my tractor. so this fall when I did my hydraulic fluid change. I changed the poppet and seat in the relief valve to see if that was the problem but there was no change in pressure but I didn't try and add shims.

Hardest part is finding where the relief valve is in the system. I tested at the rear remote location to take the loader relief valve out of the equation.