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Oil coming out of hydraulic tank breather


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#1 5030tinkerer

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Posted 24 January 2006 - 07:02 PM

I have 70's IH3200B skid steer with a Wisconsin Gas 4 cylinder engine (VF4D, if I remember right). Since I have had it, it has pushed hydraulic fluid out of the top-mounted hydraulic reservoir breather when I lower the bucket anything other than very, very slowly. The full line on the dipstick results in the fluid level being very close to the top of the reservoir. Thinking that perhaps it was not the correct dipstick, I allowed the fluid level to drop (by not refilling the reservoir when it would dump fluid out of the breather) so that the reservoir leak would not happen so frequently. This resulted in a noticable loss of loader lift. The fluid itself is not milky in the reservoir. In response to this issue, I have been through the entire machine and replaced all of the orings and hoses throughout (had numerous leaks in other areas before). I also changed the hydraulic return lines that run back to the tank and changed out the hydraulic fluid filter that is mounted in the tank. I also verified that the breather is not obstructed in any way.

Does anyone have any other ideas as to what could be wrong?

#2 5030tinkerer

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Posted 24 January 2006 - 08:44 PM

Some additional information: The fluid is overflowing from the reservoir tank. There are several supply and one return line to/from the reservoir. I have replaced the rubber return line along with all of the rubber pressure supply lines and the various o-rings at the connections. The o-rings were replaced from IH-dealer provided rings specified for this machine (same hardness rating). The only hydraulic filter my manuals show is inside the reservoir tank. I replaced this filter as part of the major parts replacement project that I referenced in my initial post. I have the ops, service, and parts manuals. They don’t show anything hydraulics-plumbing related (other than the metal high-pressure supply lines) that I have not replaced.

The only vent that I am aware of is this one that is overflowing. I can tell you that when the fluid starts coming out, it does so as a result of pressurization of the reservoir tank. When it happens, it will go for 15 – 20 seconds before stopping; about a ˝ to a full quart of fluid is lost each time. If I remove the hydraulic filler cap during one of these sessions, the overflow immediately stops. Basically, removing the filler cap allows the tank to de-pressurize (the filler cap makes a popping noise when it comes off, a lot like opening a bottle of champagne. This noise is NOT heard when the unit is not having an overflow). Air can be heard escaping the breather when I lower the loader slowly. The air changes to fluid when I lower the loader more quickly.

It should be a zero-pressure system. The breather is supposed to keep it that way. I did note that when the unit is on a level surface, powered off, and the hydraulic level is to the “full” line on the dipstick, the oil level is barely under (like an inch or less) the bottom edge of the breather (noted this as a result of taking off the breather, exposing the 3/8” tank opening).

It was just suggested to me that for the fluid to overflow, it must not be returning to the pump correctly, either from a plugged vent or a clogged pickup return filter, etc. Is it possible that my metal supply line leaving the hydraulic tank and feeding the loader hydraulic pump is partially plugged (likely from inadequate hydraulic filter change intervals by the prior owner) and that when I lower my bucket too fast, so much extra hydraulic fluid is attempting to re-enter my tank at once (after all, the return line is somewhere around 1 1/8” and each of my two hydraulic loader cylinders are three inch diameter or so) that the supply line cannot keep up with getting the fluid back to the hydraulic loader pump in time to prevent the tank from overfilling and pressurizing, thus forcing the fluid the only place it can go (the breather vent) and causing my pump to be forced to run dry?

Are there typically vents/screens inside the hydraulic pumps or anywhere else on the supply side? My manuals don't show any on the supply side, but I suppose it's possible that they do exist and one or more of them is plugged (I don't have blown-up diagrams of the pumps). One of the drive pumps had been replaced by the prior owner. The other two pumps are original (there is a pump for the left wheels, the right wheels, and the loader). No clue on the service history outside of that. Maybe a good course of action would be drain the hydraulic tank (oh joy), remove the supply line feeding the loader hydraulic pump, and check it for a blockage. If I don't find one, perhaps the next step would be to remove the loader hydraulic pump and inspect it for a clogged input screen (possibly by taking it apart – more joy). If that isn't it, I’m not terribly sure what is left. Note that starting and stopping suddenly does NOT cause this problem, nor does spinning the skid steer full left or full right and then coming to a quick halt (this leading me to believe that the supply blockage, if that is what the problem is, is not an issue for either of the hydraulic drive pumps).

Any other thoughts before I spend ANOTHER 20 hours or more on this? Am I likely on the right track?

#3 Doc Egor

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Posted 24 January 2006 - 09:03 PM

Ok...I don't remember ever working on a skid loader like this...but I'll take a crack at it.

OK...

In relation to the filler opening .... where is the fitting/opening for the vent located?

Is the opening on the side of the tank or on the top or???

If you could post a pic it would help.

First of all there seems to be something wrong here.

A "full" fluid level of 1" below the vent opening is not going to work. Any movement of the loader would cause sloshing and subsequent loss of fluid through the breather fitting.
How far below the filler opening is the fluid level at the full mark?

Are you sure where the "breather" is now located is correct?
Also...are you sure the dipstick is correct?

How about trying this....
Plug the present vent opening fitting and change the filler cap from a sealed type to a vented type?

My own Bobcat has a "full" fluid level of approximately 1/2 to 2/3rds up the side of the tank....and the breather/filler cap unit is on top (approximately 1' above the oil level.

A skid loader lives a pretty violent life in operation....
It just makes no sense that this vent is where it is on your machine.

#4 5030tinkerer

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Posted 24 January 2006 - 09:49 PM

In relation to the filler opening .... where is the fitting/opening for the vent located?

<{POST_SNAPBACK}>

Picture a rectangular tank with a threaded hole on the top center. This is what the breather screws into. It is flush with the top of the tank.

The filler neck is perhaps five inches further to the front of the skid steer than this breather. The neck extends maybe 8" above the top of the tank and is the sealing type.

Is the opening on the side of the tank or on the top or???  If you could post a pic it would help.

<{POST_SNAPBACK}>

The opening is on the top. I don't have a way to post a pic at the moment, but I can take a picture of it this weekend if need be (the skid steer isn't here).

First of all there seems to be something wrong here.  A "full" fluid level of 1" below the vent opening is not going to work. Any movement of the loader would cause sloshing and subsequent loss of fluid through the breather fitting.
How far below the filler opening is the fluid level at the full mark?

<{POST_SNAPBACK}>


Agreed. It's a lousy design. The fluid level is about 9" below the top of the filler tube.

Are you sure where the "breather" is now located is correct?
Also...are you sure the dipstick is correct?

<{POST_SNAPBACK}>

Both the breather location and the dipstick location and the dipstick location appear to be OEM. My manuals (from antiquetractor.net) depict each of these items as they are where they are.

How about trying this....
Plug the present vent opening fitting and change the filler cap from a sealed type to a vented type?

<{POST_SNAPBACK}>

Good idea.

My own Bobcat has a "full" fluid level of approximately 1/2 to 2/3rds up the side of the tank....and the breather/filler cap unit is on top (approximately 1' above the oil level.

A skid loader lives a pretty violent life in operation....
It just makes no sense that this vent is where it is on your machine.

<{POST_SNAPBACK}>

Your design sounds much more reasonable. This design is unworkable. Note that when the overflow happens, though, it does so even on completely level and smooth ground. Are you thinking that I don't have a blockage at all?

#5 Doc Egor

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Posted 24 January 2006 - 10:51 PM

Now I've got a picture in my mind of this setup....

I honestly have never seen a hydraulic system on a loader (or anything else for that matter) where the hydraulic oil tank was filled (basically) completely full!

Allowing 1" for expansion and fluid movement just doesn't seem to even be remotely reasonable.

I had a number of older DuAll loaders that had a self contained reservour in the frame of the loader....and you never filled one of those to more then 1' from the top or they would overflow when you lowered the loader rapidly.

In your case.....even with the filler tube running that 8" above the tank....that only gives you 1" inside the tank and then the tube itself to contain any sloshing and expansion.

I don't mean to be insulting....
But, do you have the owner's manual for this machine and are you sure you are checking the oil with the proper procedure and under the correct conditions?

Some systems have to be checked with the engine running and the system at the proper operating temperature.

It just seems to me that we are missing something here..... :(

#6 magicmikey

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Posted 24 January 2006 - 11:07 PM

Might there be an internal baffle over the return pipe which is bent or broken.
mike

#7 5030tinkerer

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Posted 24 January 2006 - 11:35 PM

Might there be an internal baffle over the return pipe which is bent or broken.
mike

<{POST_SNAPBACK}>

The return pipe is simply the 1 1/8" rubber hose, which has been replaced. The hose is attached to the reservoir via a conventional radiator hose clamp to a protrusion from the reservoir much like a radiator. I do not know whether the protrusion extends into the tank, but I doubt it.

The only manuals that I have for this machine are from either yesterday's tractors or antique tractor's - I forget where I got them. They are basically photocopies of what was possibly the original manual. There is no reference to having the engine running when checking hydraulic fluid. Bear in mind that when I allowed the hydraulic level to drop far enough to at least somewhat minimize the hydraulic overflow, I saw a considerable decrease in loader lift capability. Adding fluid to within the "full"/"add" hatches resolved the trouble.

I am at this point considering either tearing the unit apart again as mentioned in my second post (looking for a restriction that might not even exist!) or adding an auxiliary reservoir, connected to the original via plumbing established using the existing breather hole in the main reservoir and just attaching the current breather to the top of the new reservoir. I figure that if I give myself a perhaps four quart capacity in this auxiliary reservoir and position it above the existing reservoir and such that it has to fill from the bottom up before the breather would discharge fluid that this may solve my problem. I do continue to have the concern of potentially starving my hydraulic pump, though, if something is indeed clogged. The trouble with the clogged concept, though, is that my lift times seem quite reasonable and quick. I wouldn't think that the pump would be able to do that if I was starving it. Also, I have never heard whining from the pump.

#8 sawmill

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Posted 24 January 2006 - 11:39 PM

Sounds like it should have a breather type cap
on the fill spout,and a one way breather on the
top of the tank. The breather on top of the tank
should only let it pull air in. The breather on the
spout will exaust excess air without loss of fluid.

#9 5030tinkerer

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Posted 24 January 2006 - 11:43 PM

Sounds like it should have a breather type cap
on the fill spout,and a one way breather on the
top of the tank. The breather on top of the tank
should only let it pull air in. The breather on the
spout will exaust excess air without loss of fluid.

<{POST_SNAPBACK}>

I tend to agree with that, but the "manuals" that I have picture exactly what I have. I find it unlikely that someone would have replaced that setup with this one, but then again am also struggling with jerry-rigging this. :(

#10 sawmill

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Posted 24 January 2006 - 11:52 PM

Check the breather on top of the tank, it should
have a spring loaded valve in it. If the spring is
broke or collapsed it will blow fluid out.
I have some tanks like that. In order to save space
some outfits went with snall tanks filled to maximum
capacity. The tank breather is just a backup to keep
the tank from collapsing if the fill breather is plugged.



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