CASE 680E backhoe hydraulic pump problem??

[soapstoneguy]

Hey everyone,
I have a case 680e backhoe, not exactly sure the year but i'm guessing somewhere in the mid to late 70s since the manual says it was printed in 75.. It has recently started having hydraulic problems. i thought it was the pump because the bucket wouldn't raise, steering went out and none of the hydraulic controls were working. it made a grinding noise when it first started up and when i would give it gas and that is when everything stopped working. if i kept giving it gas then the grinding noise would go away BUT still no hydraulic controls were working. the grinding sounded like it was coming from inside the cab. i pulled the pump off, had it rebuilt, put it back on and still have the same problem. HOWEVER, now that the pump is rebuilt and back on the 'feeder' hose (thats what i call it, the one that goes directly from the hdraulic tank to the pump) gets starts collapsing when i start the machine up. when i turn the machine off it goes back to normal...i cracked the two hoses that run off the pump to see if i was even getting any hydraulic fluid and i am because they spit out some fluid.

any ideas? i'm thinking it is the control panel?? if that is the real name for it, that the hydraulic fluid gets pumped to after it reaches the pump?? not a lot of experience with this problem so any info would be great!

Thanks guys.

 

[Deon]

soapstoneguy,
I don't know anything about the 680E but if your supply line is collapsing, You need to address that problem directly. Your your pump is trying to suck
hydraulic oil from the tank and cannot do so because of something. What is it? Your hose could have internal damage that is plugging up inside due to age. The screen in the bottom of the tank could be plugged up preventing oil from entering the hose. The air vent on the hydraulic tank could be plugged. If so that could cause your tank to cave in. These are the first thing I would look into.
Goog luck.

 

[willie59]

Was the original pump in fact bad?

Take the fill cap off the hyd tank and see what it does then.

 

[digger242j]

You don't mention having changed the hydraulic filter. Did you?

 

[willie59]

You don't mention having changed the hydraulic filter. Did you?

Yep, that's why I asked about the original pump. If it went south, likely some of the debris in the filter.

 

[soapstoneguy]

soapstoneguy,
I don't know anything about the 680E but if your supply line is collapsing, You need to address that problem directly. Your your pump is trying to suck
hydraulic oil from the tank and cannot do so because of something. What is it? Your hose could have internal damage that is plugging up inside due to age. The screen in the bottom of the tank could be plugged up preventing oil from entering the hose. The air vent on the hydraulic tank could be plugged. If so that could cause your tank to cave in. These are the first thing I would look into.
Goog luck.

Hey thank you both for the replies. I did take the cap off the tank when the hose was disconnected from the pump and fluid came flowing out so i figured the line was good...but it could have just been what was left in the line. would those things you mentioned above be present as a problem even if I cracked the lines on the other side of the pump and they were dripping fluid when the machine was running? when i cracked the lines and saw fluid that is what made me thing that it was something past the tank and the pump and thinking it wasn't getting fluid to the control panel or valves (not sure of the technical names)??

i think the pump was bad, the shop rebuilt it. although i'm sure even if it wasn't bad they probably rebuilt it just to make some $$. either way at least i should be able to rule that out now lol. oh boy.

thanks for the help guys!!

 

[willie59]

Nothing on the outlet side of pump would collapse inlet (suction) hose. When oil leaves the pump, it ultimately returns to tank to start its journey over again. If it didn't return to tank, something has to explode. As for the suction line, you've either got a blockage of the inlet from the tank, or the cap is not venting allowing air in, that's why I recommended taking the cap off and check operation then. But you should change that hyd filter as well. If the pump did crap out, there's going to be some stuff in the filter.

 

[digger242j]

...you've either got a blockage of the inlet from the tank, or the cap is not venting allowing air in, that's why I recommended taking the cap off and check operation then.

I had a couple of 680 Gs, and if the E is the same, which I believe it is, you're actually not supposed to operate with the cap off. It doesn't vent--it actually holds a good deal of pressure in...

 

[willie59]

I had a couple of 680 Gs, and if the E is the same, which I believe it is, you're actually not supposed to operate with the cap off. It doesn't vent--it actually holds a good deal of pressure in...

Right digger, it is a "sealing cap". I haven't worked on a 680E, but if they're anything like the 580E, and it's been a long time since I've worked on one of those, it's possible the cap works like caps on excavators, they let air "in", but they don't vent air "back out", thereby pressurizing the tank and system. I don't know that this cap works like this, just a guess on my part, but I would try it just to see if it stops collapsing of suction hose, then noodle the problem a little more. If it still collapses suction hose, something is blocking suction line. Baby steps.

 

[digger242j]

it's possible the cap works like caps on excavators, they let air "in", but they don't vent air "back out", thereby pressurizing the tank and system.

Nope. The reservoir is an integral part of the chassis, and the cap is a threaded plug with an O ring.

Here's the page out of the 680E parts book:

http://partstore.casece.com/us/parts-search.html#epc::mr01-1431ar01-1431-440-152423

Under normal circumstances, when one unscrews that cap, you need to let the pressure bleed off, (there's a bleed hole through the threads), or else it'll pop right out of your hand. It's been quite a while, but part of me wants to remember it as actually being charged with compressed air, as those machines have air brakes, but I can't guarantee that...

 

[willie59]

It's been quite a while, but part of me wants to remember it as actually being charged with compressed air, as those machines have air brakes, but I can't gaurantee that...

Hmm, very interesting.

 

[Goose]

The 680E is set up just like a W series wheel loader. The add air pressure to the hydraulic tank to force oil to the pump. There is a pressure protection valve, a pressure reduction valve and a shut off valve in the line going to the tank. Make sure someone didnt shut of the valve going to the tank.

 

[Mattyweb]

but part of me wants to remember it as actually being charged with compressed air, as those machines have air brakes, but I can't gaurantee that...

I have a 1974 680C and this is the way mine works. Hydro tank is pressurized from the air brake compressor with ~30psi if I remember correctly. If your inlet hose is collapsing, sounds like something is blocking it. Good luck. Interested to see what you find.

 

[willie59]

The 680E is set up just like a W series wheel loader. The add air pressure to the hydraulic tank to force oil to the pump. There is a pressure protection valve, a pressure reduction valve and a shut off valve in the line going to the tank. Make sure someone didnt shut of the valve going to the tank.

Good to see a Case technician jump in here. :notworthy

 

[Tinkerer]

The hydraulic filter is in the hydraulic tank and the filter is held in place by a spring steel wire. That wire holds a screen against the filter. The hydraulic oil has to go thru the screen to enter the filter. If oil came out when you loosened the filler cap the tank is way over full. I am guessing you have a plugged screen. That would explain why the tank is so full and the inlet hose to the pump is collapsed. The tank should have a minimum of 15psi air pressure. The 680E air system is almost identical to my 680C. The air compressors are a different design on the two of them.

 

[Tinkerer]

The hydraulic oil has to go thru the screen to enter the filter.

This part of my post was incorrect. The hydraulic oil does not go thru the screen first to enter the filter. The screen is actually referred to as a relief valve in the parts book. When the filter plugs from contamination the relief valve with the screen allows the oil to bypass the clogged filter. Before I bought my 680 someone must have had a badly plugged filter and screen. The first time I changed the hydraulic filter I found that someone had tried to repair the screen by soldering it . The solder repair had failed. That created a potential disaster for the hydraulic pump if the filter plugged again. A new relief valve was available thru the local Case /CNH dealer.

 

[soapstoneguy]

This part of my post was incorrect. The hydraulic oil does not go thru the screen first to enter the filter. The screen is actually referred to as a relief valve in the parts book. When the filter plugs from contamination the relief valve with the screen allows the oil to bypass the clogged filter. Before I bought my 680 someone must have had a badly plugged filter and screen. The first time I changed the hydraulic filter I found that someone had tried to repair the screen by soldering it . The solder repair had failed. That created a potential disaster for the hydraulic pump if the filter plugged again. A new relief valve was available thru the local Case /CNH dealer.

thank you for the reply and help. Sorry i haven't been on in a while, been waiting for the weather to clear (don't have a shop, work on everything outside). anyway, the pump was rebuilt, filter was replaced and hydraulic tank was cleaned out THOROUGHLY and new oil put in. Started it up, still had the grinding noise so I took the hydraulic tank cap off and the grinding sound kept going...looked at the main hydraulic line that feeds to the pump and it was still collapsed right where it connects to the pump....?? Anyone got any ideas? I can't imagine it would be the main hydraulic line that is bad and I know no one has shut any valves because I'm the only one who works on and runs the machine...

Thanks for the help everyone. Been trying to figure this thing out.

 

[willie59]

I know you stated "filter was replaced and hyd tank was cleaned thoroughly", but if you're still collapsing the suction line going to the pump there almost has to be something blocking that line.

I worked on a Komatsu D41P-6 dozer once, main pump was trashed. Fitted a new pump, within a few hrs the oil heated up and trashed the new pump. Somewhat baffled at this point, and being a load sensing system and a gear pump, I replaced the load sensing and control parts in the main control valve. Fitted (another) new pump, within a few hrs oil heated up and trashed (another) new pump. :Banghead

Mad as hell at this point, I told my helper "we're going to take every hose, every fitting, every part of this hydraulic system apart until I find what's causing this problem. Started with draining and removing the hyd tank. Upon removal of tank, found a stick, yes, a stick, inside the first elbow of feed line from tank to pump. There's no way a person would have seen or found this stick in the line until tank was removed.

The stick was causing severe restriction of oil flowing to pump, restriction was causing cavitation in pump, cavitation was causing rapid destruction of pump. Once it was removed and sorted out, haven't heard from that machine since. :drinkup

 

[alrman]

Is this suction hose very long? Is it still the original? There is the possibility it may have been replaced & not be a hose suitable for oil.
If it has gone soft it will colapse as the oil is sucked through it - without any restriction.

 

[Tinkerer]

Started it up, still had the grinding noise so I took the hydraulic tank cap off and the grinding sound kept going...looked at the main hydraulic line that feeds to the pump and it was still collapsed right where it connects to the pump....?? Anyone got any ideas?

First do not run the engine until determine what is causing the suction hose to be collapsing. Or you will be trashing the pump if it isn't already. I would unhook the discharge air line from the compressor on the engine. Next hook a shop air compressor onto that line and put about 100 PSI into your entire air system. With the engine shut off and the hydraulic tank cap OFF, determine if you are getting air into the hydraulic tank. You should be able to hear a loud hissing as the air enters the tank. If you don't hear it or it doesn't sound like much air is coming in you need to find the problem in the air regulator that is next to the tank or if somehow the shut off valve is restricted or even closed. If all is good in the air supply and proper pressure can be put into the tank you have it narrowed down to the suction pipe and the hose that couples it to the pump. That coupling hose should NOT be collapsed with the system up to 20 PSI. If it isn't ,start the engine and quickly observe the condition of that hose. And I mean quickly ! Because if the hose collapses you have a real problem in that supply line and you will be on the verge of running the pump dry. Keep us posted what you find.