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midnightpumpkin

Powermax rear lift troubleshooting help needed.

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midnightpumpkin
I have two Powermax's one a 4040 and the other a 4041. The 4040 rear lift is very strong, we have a fork lift like carry all on the 3 point hitch. I have not been able to put enough load on the carry all to overload the rear lift hydraulics. The 4041 rear lift is comparatively very weak. The carry all on the 3 point will not lift my weight (220 lbs). Same with down pressure noticeably weaker than the 4040. I put a pressure gauge on the implement test port on each unit. They both read the same, 500 PSI at the end of the stroke up or down and 300 PSI while the stroke is in motion. With the control lever in the mid point position the system reads 0 PSI. These reading are not totally consistent with the Powermax repair manual, but do seem reasonable. So where am I loosing hydraulic pressure in the 4041 and where should I do additional pressure tests? Can the control spool valve wear out and cause pressure to bypass the cylinder? I am hoping some of you with Powermax experience will chime in with some thoughts/tips on this issue. Thanks John U

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midnightpumpkin
Marty, why would you suspect the cylinder and not the control valve? I am thinking I should measure the pressure going to the cylinder on the 4041. I would think that at full stroke, the pressure at the cylinder should be the 500 PSI I measured at the relief valve on the pump. If it is less then the pressure is being lost somewhere, since no oil is going on the ground it would point to the control valve. I am answering my own questions here! The next question would be can these spool valves be rebuilt. This a a dual valve, BTW, the front cylinder will lift my lard _ _ _ standing on the plow blade, which again suggests the problem is in the side of the spool valve which controls the rear lift. Your comments are welcome and invited. John U

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midnightpumpkin
Ok, Marty are you thinking the double acting cylinder might be leaking through?? I will take your advice and swap cylinders tomorrow. Wilm169 My gauge will read up to 3500 pounds, but the pressure relief point on both tractors reads 500 pounds on the gauge. The gauge may be wrong, but the readings are the same on both tractors. John U

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D-17_Dave
First off, you need a 1500PSI gauge to test the lower pressure system. At 3500 face you can't see enough variance in 300 PSI and the calibration of the gauge may be off that much. Next, get the repair manual for the tractor and go through the test ports starting at the hydro. Since you have 1 charge pump doing several things at once you need to determine what pressure you have to start with at the hydro. Now the hydro has a couple of relief valves built in it for each circuit. The spool valve also has a relief valve built into it but is useless if there isn't enough pressure to actuate it. Keep in mind that you won't get any pressure reading until you load the oil and create resistance.

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acfarmer
Just guessing I'd first check the relief valve for a problem.If the hydraulic will hold up what its lifted for a couple hrs then you can just about rule out an internal leak in the cylinder

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midnightpumpkin
quote:
Originally posted by MPH
Try swapping the cly from the 4040 to the 4041. Be my first guess.
And Marty's first guess was correct. Put the front cylinder on the rear lift and it will now lift anything I am able to put on it. Now to try the weak cylinder and see if it can lift the front blade. John U

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DMedal
This is a really interesting problem, I'm looking forward to hearing more. A couple of questions to maybe narrow things down: a) when you swapped cylinders, is that ALL you swapped? or did the hoses go with? b) You say it won't lift your weight. Will it hold your weight once it is up? c) how is the speed of the lift, unloaded? d) doesn't leak down over time pretty much excludes the cylinder, as Dave said. Restrictions would not reduce your lifting capacity if you are patient, but would slow it down. If you swapped only the cylinders, then you've got a bad cylinder. (obviously) But a bad cylinder would leak down, lowering the load over time, fairly rapidly if it is enough to cause the problems you list. So what is wrong with it? With the aid of this group I can pretty well assure you that you'll find the problem. -Don

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D-17_Dave
quote:
Restrictions would not reduce your lifting capacity
This is true as long as the restriction doesn't cause the oil to go over the relief valve. If the hose/fitting is almost completely blocked, the oil flow could go over the relief valve and reduce the pressure going to the restriction enough not to actuate the cyl. with a load. Just food for thought.

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midnightpumpkin
I never said that the bad cylinder would hold a load or not. Never tried it. This tractor has a front and rear cylinder, it was the rear that was weak originally. I swapped the cylinders only, same hoses, same everything except the cylinder. The weak cylinder remains the weak cylinder. Fortunately the weak cylinder is strong enough to lift the front blade which is all it needs to do. End of story. John U

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midnightpumpkin
The weak cylinder was originally the rear cylinder on the tractor that was used with a salt spreader on the 3 point hitch. The entire back end of the tractor was heavily corroded from the salt. While the rod coming out of the cylinder was not visibly corroded, I suspect the salt penetrated the internals of the cylinder. (Salt actually got in the fuel bowl and corroded the float pivot in the carb) John U

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UCD
If the cylinder is weak the 0-rings most likely are worn and leaking by and need to be replaced. this is an easy job. I dought that salt got into the carb and corroded the the float pivot. More likely water in the gas

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midnightpumpkin
quote:
Originally posted by UCD
If the cylinder is weak the 0-rings most likely are worn and leaking by and need to be replaced. this is an easy job.
This cylinder is welded on both ends. It would have to be cut apart and re-welded. John U

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npalen
The 3PT on my Allis 720 slows down considerably after the transmission warms up. It does seem to hold the load okay when raised but will gradually drift down over a couple hours. I understand that the two valves are supplied by the charge pump on the hydrostat. Any thoughts on what I should check first? Thanks Nelson

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scr
I have a Powermax 4041 with a weak rear lift. I'm only getting 350-400 psi at the front quick disconnect. I've read the post Midnightpumkin had abnout his lift problems. My question is where are the relief valves located on the Hydrostatic pump/motor and where is the one on the cylinder control valves? Also how do you adjust the pressure? Thank you very much.^ Steve

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D-17_Dave
Steve, the pressure relief valve for the lift is located under a capping nut on the spool valve. Remove the dash sheet metal wrap around and the valve is assesable. While holding the lift lever against dead load with a gauge adjust the relief valve screw with a flat head screwdriver inward to increase the pressure. You'll have to loosen the jamb nut on the screw while doing this. If no change is noticed then the relief valve in the tranny is dumping ahead of the spool valve. This relief valve is adjusted by shimming the relief cartridge. Obtain a copy of the repair manual and carefully follow the instruction when messing with the pump. An error here could be costly.

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