I suspect that my marklift 62 foot boom hydraulic pump may be sucking air when it starts making a loud noise when I engage any of the boom functions such as lift or extension or rotation. This happens on every function and the function will operate normal for anywhere between 2 to 5 Seconds before the hydraulic pump starts making a loud noise and the function stops until I activate the function again a few seconds later. So for example, the Boom Lift will only rise about a foot or two at a time before it's stops and the main pump makes a loud whining noise, as if it is out of fluid and pumping air. I see no sign of a leak or dripping between the hydraulic fluid storage tank and the pump suction line. The main hydraulic filter is on the return lines just before the storage tank. I'm wondering if perhaps there could be debris in the bottom of the tank where the suction line goes to the hydraulic pump? Or if there is some kind of an air bleed knob for the main pump? The pump sounds normal when I engage the foot pedal in the basket before engaging one of the feature valves. so therefore it seems okay with the Pilot low pressure around 200 lb. It's just when I engage one of the features and the high pressure kicks in that the pump stops after several seconds. Should the hydraulic pump clear out any air in the lines on its own if I let the machine run for a minute or two before engaging any features?
You don't see any leaks, did you check the oil levels?
View attachment 187933 It's a 40 gallon oil reserved tank and it is about half full. I checked it with the dipstick. I have been reading the service manual some more and read that there maybe some filter strainers at the suction inlet hose to the pump as well as more strainers at the inlet hose to the pilot valve spool manifold that could be clogged, but I wonder if that would cause the pump to make the loud high pitched whining noise after several seconds when a valve is turned on? I also read that the pilot valve circuit has its own separate canister filter, pictured, and wondering if it might be clogged? It has a red and green indicator, pictured, but I don't know what each color designates. It's currently showing kind of a reddish purple color, but changes to Green if I press down on the top button with my finger. Does that mean it's clogged since it's showing red? Does this filter all of the functions as well as the rotation pilot valve? I asked that because the hoses to and from that pilot valve filter enter and exit over the rotation pilot valve, pictured.
Where does your sump draw from? Is there a chance you're sucking air? Filter service never hurts, especially that one with the filter indicator
I don't know what the word dump means? Would that be like from the larger main filter that empties into the top of the hydraulic oil 40 gallon storage tank? Also I don't know what ducking air means. Sorry I'm new to all of this. I can't believe how complicated this boom lift is compared to my old farm tractors LOL I really appreciate all of your help!
Stupid autocorrect. I meant to say sump. Is your sump fully submerged in oil, or does it have the potential to draw air with it? As opposed to "ducking" air was supposed to be, sucking air. Bottom line, if you have a sight glass on your tank, your oil level should be in the middle. Filters, most definitely need service. Before that , any of that, follow the biggest hose off the closest to bottom of the tank towards the pump. Is it damaged anywhere, is it loose at either end. If you pull tug on or flex it, will it leak oil? Is there a shut off valve at the tank that someone bumped? Is it kinked? Now to the top of the tank, what kind of cap does it have? Does it look like an upside down oil filter? Is it a big pipe cap? Is there any kind of breather on top?
Well, I guess pictures can probably explain it better than I can but I'll try. I'm guessing when you say sump, that must be a second compartment in the large hydraulic tank like a septic tank and that the large main hydraulic filter empties into at the top of the tank on the end. And it looks like the exit from the tank is at the other end on the bottom going towards the pump. And there is a shut off swing valve there as well. And the large 1 inch diameter hose from that valve is a straight run to the pump, and there are no bends or Kinks. But I will go ahead and shove it around just to see if I can get it to move. The area below that one inch tube was also dry . Anyway I just noticed this for the first time, that there are 4 more smaller hoses entering the same end of the tank as the large filter and 3 are located halfway up the tank and one at the bottom. There is no sight glass, but there is an oil level gauge, and the interesting thing about it is that it looks like it should measure oil level on two compartments of the tank, but there is only one arrow pointing to the right side of the tank, see picture. Also see another picture showing the cap of the tank, and there is no little pin hole on the top of the cap that would allow it to breathe.
so if the hydraulic storage tank had a vacuum, would that cause the hydraulic pump to stop pumping or make a loud whining noise?
Yes, your pumps would be fighting negative pressure in the tank.
So one simple test might be to just take the cap off the tank and see what happens? Thanks much!
Worth a try
Any idea of a good cheap source of parts for my 1980 marklift 62 boom lift? To my knowledge the marklift parts are available through Genie and Terex. I'm having a real difficult time with my current supplier Access Platform returning phone calls and emails and canceling online orders without explaining why.
Well, here is some great news! I found this pictured screen filter on the sump side of the hydraulic tank and when I removed it, the pump worked just fine. But when I cleaned the screen filter and put it back on, I discovered that the pump would suck air depending on how much of that screen filter was submerged in oil. And it turns out that the tank has to be half full of oil to completely cover that sump screen filter. So my first question is this 1980 Mark lift calls for Dexron 3 transmission fluid, and I'm wondering if I could just add regular hydraulic oil to mix with that Dexron fluid that's already in the 30 gallon tank? If not, I'm wondering if I could just substitute hydraulic oil completely for the transmission fluid? Transmission fluid is a good deal more expensive than hydraulic oil.
If it's a man lift, I'd stick with what oe calls for. You dont want jerky operation where a people is concerned.
Thanks Fun. I will follow your advice. Just out of curiosity, what is it about ATF fluid that makes it less jerky than regular hydraulic fluid?
It's just a much lighter oil. It may or may not respond better to proportional valves then hydraulic oil in cold weather Not knowing any better I once used hydraulic oil in a Hi ranger man basket truck the customer came back reporting jerky hydraulics that's why now I try to stick with what they recommend. I believe ATF to be on the equivalent of an SAE5 or 10 whereas hydraulic oil is probably closer to an SAE20
Thank you so much, great advice! I can't tell you how relieved I am 2 learn that this problem I was having was just from that sump screen filter not being fully submerged in oil. I'm amazed that the service manual had no comments about that. It also occurred to me that I will probably have to have even more oil in the tank in case I am driving the man lift uphill to make sure the filter stays covered up as the tank tilts upward.
I would guess that tank is designed to hold all the oil of all the empt the collapsed cylinders enough so that you can extend every function on the machine to full extension With out starving the pump. I agree the manual should have been more clear about how much oil is actually required
So if all of the cylinders are fully extended, I would assume that the sump screen filter would still have to be completely submerged in oil to keep air from being sucked in through the top part of the cylinder-shaped screen filter? Which leads to another question, I'm wondering if I had a screen filter that was shorter then the one I have if that would give me more usable fluid in the tank? Also wondering how all of the metal filings in the screen filter before I cleaned it could have gotten in the screen filter when they are supposed to be heavier than oil and gather at the bottom of the tank?
Quite possibly could have been there since it was born. I agree, shorter filter would be better
Thank you so much for all this great advice.
So I have a possible solution to the filter sucking air. Instead of going with a shorter filter, I was thinking I might just put a 90-degree elbow where the filter attaches to the bottom of the inside of the tank which would put the filter horizontal about an inch off the bottom of the inside of the tank. And that would keep the same flow rate specs on the same filter . Your thoughts on that please? And if I do proceed with the elbow, I'm wondering what kind of material, plastic PVC would be the most economical, but I'm wondering if galvanized would be better and I'm wondering if it would not oxidize since it would be submerged by the oil and not exposed to air and water? if not PVC or galvanized, what other materials for an elbow would you suggest? I'm thinking brass, but that would be awfully expensive.
Plain old iron. No coating. NO PLASTIC!!!! It'll deform once it gets warm. I would use a couple 45*s . Pressure, whether positive or negative doesn't like bends. Every 90 drops flow rate by a significant amount, I don't recall exactly but it's not good on the negative side. Laying it over is not a bad idea. As long as overall height is diminished to achieve what you're after
Thanks so much! I will definitely take your advice. Seems like all I've seen at my local hardware stores is Galvanized, brass and PVC. Wondering where I would get just plain old iron, at a hydraulic shop?
You could try a hydraulic shop, farm supply, or home improvement stores. Hydro shop would be my last choice. They're gonna be the highest priced. Maybe Google fastenal or motion industries.
Somehow this machine managed to run since 1980 without any troubles, but now you need to remount the filter/screen? Nothing has changed on the machine. I think you may be trying to reinvent the wheel here. With the boom fully retracted, you should have the fluid almost to the top of the hydraulic tank, like 2-3" down in warm weather, a little more than that in cool weather 4-6" (warm weather makes the oil expand). Don't go mixing around with the oil. If its ATF now, just leave it ATF. With that screen pointing up on the bottom of the tank, it shouldn't matter if its completely submerged, as long as it can flow enough to feed the pump. If it was extremely clogged, it might not flow enough- get a new filter. But with the boom retracted- like it should be driving around- you should have all kinds of oil. Your tank should be almost completely full of oil when driving around retracted. If you've only got a 1/2 to 1/4 of a tank of oil in it, as soon as you shoot out boom, the pump runs out of oil. Pumps starving for oil is really really hard on the pumps. Tank should be full with boom retracted. Don't trust the gauge, put a screwdriver in the tank to see how full it is.
Thanks for all that great advice! The 40 gallon tank only had 15 gallons in it so I went out and bought another 25 gallons. I don't know how old that 15 gallons was and if it was too thick to easily pass through the screen filter. So I'm going to drain out that 15 gallons, and add the new 25 gallons and see if that flows through the screen filter when the screen filter is not completely submerged and see if the pump still sucks air.
How did you get the screen out of the tank?
It unscrews. Since it is too hard to get a wrench on the bottom of the screen filter because of the curvature of the bottom of the tank, are used a rubber filter clamp tool like what you can get at Harbor Freight for a few dollars. The rubber strap will grip the screen without damaging it too much like a pipe wrench would do. You can also try to grip the very top portion of the screen filter so you're not damaging the screen pleats.
Bus, I also discovered that you have to have enough oil in the tank to keep the screen filter completely covered even when it draws down the oil level when various extension and lift cylinders are being filled with hydraulic oil. You can also experiment with the screen filter completely removed to see if that gets more flow to your hydraulic wheel Motors.