Yes guage is in good place.
What you testing is new pump and TLC main relief if that good then drive motor is bad.
The 224 drive always going to be weak it design to give power on low height tire the loader never work satisfactory with low profile drive motor, but should show good pressure when stalled.
Some things to test in future we get there you have best loader out there.We set main relief on PTO then one on travel control valve, the problem low pressure not found yet getting plugs are caps is best place to start.

 

I agree with bowl builder. Best looking 646 that I have seen.

doublet

 

Is this problem coming from the TCV, the relief in it, or something messed up inside it, just wondering. If PSI for relief not set high enough, putting load on tractor would make it start to open, not sure if this has anything to do with it, but make sure reliefs are set correct on the TCV & PTO, something telling me to make sure those are set right.

 

Capped both lines from TCV to drive motor. :mechanic:
-Full throttle. Oil, cold.
-Neutral-0 psi.
-Forward, pedal depressed,pressure holds at 1600 psi.
-Reverse, pedal depressed, pressure holds at 1600 psi.
-No squeal.

 

Overall these readings don't look too far off to me.

I've often noticed that the tiller motors will bypass oil when hot and loaded heavily, hence the loss of pressure over time. These are not overpowered mechanical drives ... you will need to feed the tiller at appropriate rate in hot loaded conditions. It is, after all, tearing down 41" at a time.

As for the 1600PSI cold w/travel control, that seems to me to indicate a little more spool adjustment could be in order. Not sure ... but possible. You seem to have good pump output and not hitting relief. If the spool is slightly open still (not 100% passing to the motor) then it might just not be at peak torque/pressure. That would just get a bit worse (lazier performance ...) as the oil heats up.

If you are going to run the tractor good and hot, switch up to 20W50 if you aren't already there. That will help some. (I don't recommend using 20W50 in cold weather ... or if you use it only occasionally, give it good warm up time).

My 2c

Brian

 

I am following this thread with a lot of interest as my 648 loader is more or less behaving in a similar way with a good drive motor, full spool travel and existing good pump.

Since msy6280 has isolated the pump with the capped travel valve and still has low pressures with his new pump, is it possible the spools and bore are worn on the valve? I don't have much hydraulic experience, but I understand the spool valves isolate the oil path through the clearance between the spool and bore, and the O-rings only seal the outside. Not sure if that could be a possibility or not.

 

msy6280
Great work on you part now time turn up pressure on main relief start with TCL if go up by half turn on relief instead 1600 may go up to 2,000 are may just set right there on 1600, but does move adjust to 2250 psi and stop with that relief.
As we see your gauge gain 100 psi by capping off drive motor so losing 100 psi not bad at all because gerotor motor and drive motor is good.

Step 2 move to PTO lever and work that check pressure first you need to get ready so take off tiller lines make both female disconnects on ports of pto valve this give you deadhead out ports that what want be like same as TLC check.
Whatever gauge reads set to 2350 psi you want 100 psi difference in to main reliefs.
Its possible we want get to pressure golds if reliefs are bad are pump I now new but some egg are cracked.
I'm looking forward to your next post on what find TLC relief and PTO relief.

I no I'm off from what manual says for relief setting we going to give pump easier life time.

The squeal not sounding is one indicator pump bad if want set up to 2250 that confirm bad pump.

 

vfrman91

Its not worn spool valve only lubrication oil go by spools there are what called A, B, C Spools A standard size bore line bore honed if have known problem with spool best just get used part.

 

I adjusted the high speed to 3600 rpm. I left the tractor set up with the gauge the way it was for the last test.
-Turned relief screw in one full turn.
-Full throttle, pedal depressed the pressure held at 2200 psi for about one minute and slowly dropped to 1000 psi.
-Turned relief screw out two full turns. The pressure spiked at around 1500 psi and dropped quickly to below 1000 psi.
-Turned relief screw in three full turns(this felt like it bottomed out the screw). The pressure spiked at about 2200 psi. and dropped quickly to 1000 psi.
-No squeal yet.
-I started the test with cold oil, so the quick drops may be because the oil was warming up?

 

Okay time to go to PTO relief un connect tiller lines no lope hose hook up we want those ports blocks. Work with that relief as did TCV relief set at 2300 if get there. leave travel ports block until problem fixed we need blocked later. The fall in pressure at tcv to 1,000 psi is a indicator of bad pump If PTO main relief does same we got pump cornered.
As hold pressure on high it falling slippage in pump it okay hold it for few seconds but oil get hot not being moving.
The relief screw all way down that another indication bad pump all relief need to be back off to zero on next new pump install and pressure walk up for break in new pump in other words we not going force new pump to maximum pressure.
You doing great job on your testing reporting back thanks.

 

Plugged both work ports. At full throttle the pressure held at 2200 to 2400 psi. When I depressed the pedal it dropped fast to around 500 psi.
I removed the TCV relief screw and pulled out the spring.
It looks broke to me. Did I find the problem?

 

Yes that broke spring is problem there small pieces some place in system but down spend time looking for it.
That great PTO pressure was working right that tell story something wrong with relief spring in TCV.

Call on michianfan Dan White for good spring these springs have to same as original a Dealer may have one in stock new on this item is good way to go.
New and pressure up system your finish I just Love 10 dollar repairs enjoy your tractor.

 

Thank you to everyone one who helped with this, especially "gator" for talking me through the pressure testing. I'm sure the broken spring is the problem, but I'm more than a little concerned about where the other piece of it ended up.

 

I found the other part of the spring, it was about a 1/4" long. I got a new one from Brian, along with more instructions for setting the relief. With the bucket against a tree, PTO engaged and in high range I got around 2150 psi. In low range it would spin the tires. I hooked up the tiller and headed for the garden. After about 30 to 40 minutes of tilling it lost all power again. It hardly had enough power in low range to pull itself through the soft soil. :crying: :crying: :crying: :crying:

 

Its time for new pump as you using a tiller my pump choice would be a little higher than factor .61 cubic inch go to .67 are .72 and you have better perform hydraulic system just don't go higher. You need pump that has set back ports so PTO line hook up not one with center ports on pump a stock pump going to be better than what have gear slipping oil when thin and hot.

 

Still the same after it cooled off?

Brian

 

I didn't try it again. I decided we both needed a little time to "cool down".
I'll try it again tomorrow. :thumbsup:

 

I wanted to find the real numbers for cold and hot operation so I installed the gauge on a T by the quick-connect fitting so I could switch to a line loop test as soon as the oil got hot. First I did three tests with the oil cold, then I did them again after I tilled until it lost so much power that I could not move at all in the soft soil when I put it into high range.( I was tilling in low) I had to shift back to low to move.

With tractor at full throttle and PTO engaged.
-Bottomed out mid lift. Cold oil- 1600 psi. & Hot oil-1500 psi.
-Bottomed out bucket roll. Cold oil- 1500 psi & Hot oil- 1500 psi.
-High range with bucket against a tree and travel in full forward. Cold oil- 2100 psi. & Hot oil- 1100 psi.
-Oil temp. after testing was about 190 degrees. This was with a cheap cooking thermometer, so I 'm not sure how accurate it is.

 

If the pump is bad, shouldn't all the psi numbers drop,instead of just the travel psi?
Just wondering....I'm here to learn :thumbsup:
Also, when I bottomed the bucket roll cylinder I did get a squeal from the relief.
Doesn't that mean that there was more pressure available, but the relief is set at 1500 psi ?

 

Its about volume you lift uses less volume from pump and cylinder never bypass any that volume like a motor does a motor uses flow then goes back to reservoir to be pump again. The lift also set at lower pressure than motor there 2 reliefs in valve bank one for main travel other for lift. A pump looses volume because wear from gear wearing in to housing are inter parts failure.
In other words pump has failed down below high pressure relief but not below lift relief.
The reason for high then low pressure oil slipping heat real fast in pump as fast as needle drops.

 

I don't often disagree with Gator on things hydraulic, but here we depart.

In a stall condition, this is not about flow capacity. It is capable of 2100 psi cold, and holds 1500-1600 on the lift circuits. Stall condition pressure readings should be taken at 1/2 to full engine speed to ensure it's not just basic low speed pump bypass.

I presume we've got the right oil in this tractor ... low viscosity hot will make the drive motor easy to bypass and hence minimal pressure build up. Should be 15W40 or 20W50 motor oil.

A low stall pressure could also indicate the spool really is not fully traveling with the banana plate, though I think this was also discussed. If the spool is partially open, hot oil bypasses the stalled motor and won't build up as much pressure. A very common problem and new banana plates, the common wear culprit, are in stock ready to ship for less than $30.

If all those are really good ... you may actually have a drive motor issue. I've not seen many actually bad motors ... but darn if we did not just recently totally restore the drive power of a 648 with a new drive axle motor.

Remind me ... before the new relief circuit spring (yours was broken?) did you ever see those kinds of pressures before?

Brian

 

We talk about this on phone this after noon late his problem has been found the right spring is being gathered up he could not raise pressure because low tension spring are pick by load on them.
A main relief has range as pressure goes up are down usual these spring have color code think marking with different nail polish color red green yellow white no sparkles lol.
The flow does maintain a same pressure on like cylinder no oil has anywhere to go on motor has leakage by rollers he was setting pressure by screwing relief set screw in until made cold oil pressure think a gap between ball and seat after oil hot thin oil flowed faster at this small gap and had lowed pressure down to 1100 psi because flow lost.

 

The new spring I ordered, and installed was the wrong one. The Case part# substituted to a spring kit. It was a kit for the lift side instead of the travel side. This is a weaker spring and I found out that a weak spring acts the same as a broken one. After several phone calls and more help from members I located a used OEM spring. "oldcasecoltguy" had one. Because I had a lot of outside work to finish before it got too cold,I did not get it installed. And now it looks like I just sold my house and bought another one, and will be moving before the end of the month. If everything goes as planned I will go from a house and garage on one acre, to a house with no garage :facepalm: on fifteen acres, so I will have to wait until next spring to work on it again. :mechanic: