Hi all, I recently bought an old 1975 M-620 but am having some issues. when trying to move the pumps whine badly and fight against the sticks. I pulled off the vane pump and it looks really good inside, you can still see the wave hone marks in the bore. If you move the sticks just a bit to crawl along it dosent whine much but as soon as you increase the load it starts whining and fighting you back. I dont seem to find a tag on the pump anywhere, would anyone know what model vickers pumps this uses? Any assistance is greatly appreciated. Tom.
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Is it hydrostatic dives or clutches?
Or are you talking moving the stick to operate the hydraulics?
If its hydrostatic you should have 2 hydraulic drive motors, one each side. If you have that and you hear screaming and the sticks fight you it sounds like a suction line filter. On the later model machines with vickers pumps there is a square block on the top of the hydraulic pump, there is a hidden filter behind the middle fitting on the left side. I have no idea if yours is the same or even close i just know it was an issue on a 1978 731 i owned.
If you can provide pictures of the pump that may be of assistance too.
Or are you talking moving the stick to operate the hydraulics?
If its hydrostatic you should have 2 hydraulic drive motors, one each side. If you have that and you hear screaming and the sticks fight you it sounds like a suction line filter. On the later model machines with vickers pumps there is a square block on the top of the hydraulic pump, there is a hidden filter behind the middle fitting on the left side. I have no idea if yours is the same or even close i just know it was an issue on a 1978 731 i owned.
If you can provide pictures of the pump that may be of assistance too.
Hello Tazza, This is a fully hydraulic unit, no clutches.
I'm talking about the sticks to operate the wheel motors, I checked for a bronze filter behind the inlet fitting but no such animal.
I have some pictures but cant for the life of me figure how to insert them.
I'f I can ID the pump then maybe I can search for a book on it
Thanks
Tom.
Don't sweat it, the pictures are more than good enough.
The pump isn't the same as what is used ont he later machines like i thought it may have been, they run a vickers TA1919. Is there anywhere you can check your charge pressure? it could be your problem. Can you run it and make it squeal and fight against you, then check the oil in the tank, is it foamy? or any signs of bubbles? if so, its a sign of cavitation which is caused by air in the system or a blocked/restricted section line
I dont quite know if it even uses charge pressure. Theres no internal ports from the vane pump into the main pump, and no direct pressure lines that I can tell.
It appears that the vane pump feeds the valve block, then the return line from the block Tee's in to what looks like a bypass or dump line that comes off the side of the main pumps and loops back to the suction line on the vane pump. Its a little hard to put into text.
The oil does get foamy so its definately cavitation, but I cant find the source of it.
Tom.
sterlclan
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it must have some kind of charge pressure it is needed to make up for lost oil in the drive loops. is there any filters on it? it could be that the piston pumps are getting worn, they must have some kind of wear plates in them and if they aren't worn to badly they can be fixed with sandpaper and oil..... check the simple stuff first, no kinked or squished lines, bad oil/air leaks at a fitting or hose? plugged inlet line to the pump?.......if you raise the arms and then try to move the machine while dropping the arms does it move any better? ..........Jeff
The charge pressure system is tricky, its done with the returning oil from the oil cooler and not direct from the pump. Oil from the pump is about 2,500 PSI and charge pressure will be around 100-120 PSI.
I too would start with the simple things, changing filters. It could very well be pump wear causing problems and as mentioned, these can usually be repaired with a sheet of glass, oil and wet and dry sand paper. It takes some time and patience but it does work, Jeff and i are proof that it can be done, and cheaply.
In the last picture where the guage is there is a spin on filter, I thought that was a return, maybe thats where it should get its charge pressure.
One end goes to the hydrostat the other end is tee'd into the return from the valve block and goes through a check valve to the suction line on the vane pump. I'll pull those apart and see if theres anything wrong with those bits.
Thanks for giving me some direction, I'll report my findings this evening.
Tom.
mllud
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Tom Steerclans sugestions about checking the hoses for air leaks. Have you checked the hose that hooks to the tank all the way to the pump.The suction side can sometimes draw air into the system without appearing to leak.I had the connection at the hydraulic tank cause problems.It was loose enough to allow air to be drawn in but didnt appear to be leaking any oil.Mike
The suction lines appear good but I think I'll give the clamps a little tweak anyhow and see if it makes a difference.
I checked the checkvalve and the filter on the side that should be the charge pressure and see nothing out of whack so back to square one, and I'll put a known working guage on it and see if theres any pressure there.
Thanks for the suggestions guys, If you think of anything else please post.
Tom.
Finally, Progress!
Turns out the checkvalve is bad, I pulled it apart and the seat is leaking, I polished it down a bit to get it to seal enough to get 50PSI charge pressure and the machine actually has some power now. I'll pick up a new check tomorrow and I should be back in action. ( all this just to do yard work.. lol )
Thanks again.
Tom (A happy camper).
