Hi All Having finaly sorted the turning joint on a Case 688 wheeled excavator, we have a further issue. If you press the brake pedal, the wheels twitch as the drive motor operates and when moving, the brakes are applied. A further symptom is that it will not run in high gear. Now the turning joint has been re-built and we did find an issue with some seals inside this. Is there a connection between the brake and accelerator and if so where (I would guess in the pedal box?) I would guess that there is as you would not want the hydraulic drive operating when the brakes are applied. I do have some manuals for the tracked version of this machine but sadly not the wheeled one. Any pointers would be most appreciated. Mark
Ok, still getting no further forward with this sadly. A further description of the symptoms are: The wheel brakes appear to be working ok and we have isolated the transmission brake yet we still get a strong braking force through the transmission. I am assuming this is related to the drive motor (is there some sort of clutch setup between the motor and box?) In addition, when the brake is pressed, the wheels turn in a backwards motion until the brakes apply. Similarly, if traveling backwards slowly and pressing the brake gently, the machine speeds up!. This all seems to point at some cross feed between the brake circuit and reverse drive circuit. So, any thoughts?
I have woked with 1088 and 1188,I will try to tell you in my poor english how i remember that,when you press acelerator the engine go up revolutions,when you release the acelerator the engine go down revolutions,there is some kind of sensor on it,brakes working at independent way between them,the hidraulic transmision engine needs at least 350 psi for working well,check it that,above all when you run at high speed...I don´t remember more, it was a long time
Could it be possible that one or two of the lines going through the swivel may have somehow been crossed?
Anything is possible (although we have checked as best we can, drawings for these wheeled units are hard to get). This fault was present before the swivel was removed (and at the time the diagnosis was a failed swivel joint causing the fault).
I am not familiar with your specific piece of equipment, but will try help you out. A couple questions first: -Is your throttle pedal mechanical linkage, hydraulic piloted, or electronic? -Verify that the drive system is hydraulic motor driven (hydrastatic drive) versus mechanical drivetrain? If so, does it use a rocker type drive pedal? -Does this have a seperate brake pedal for stopping only? -Do you by any chance have a hydraulic schematic for it?
Thanks for the Reply MTI Mark Is your throttle pedal mechanical linkage, hydraulic piloted, or electronic? It is hydraulic piloted -Verify that the drive system is hydraulic motor driven (hydrastatic drive) versus mechanical drivetrain? If so, does it use a rocker type drive pedal? The drive consists of a hydraulic motor with a limter attached, this in turn drives a 2 speed gearbox with prop shaft driving the front and rear axles (it is a wheeled unit). It is not a rocker type drive pedal, it is more ackin to a throttle with direction control being performed by a sperate forward/reverse selector. -Does this have a seperate brake pedal for stopping only? Yes it does. -Do you by any chance have a hydraulic schematic for it? Sadly not, I have a set of manuals for the tracked version but, have not been able to obtain any for the wheeled unit. So far we have been utilising the European Case Parts website for diagrams etc to try to work out the functions. I should add that we have had two Case Techs look at it (at great expense) with the first offering no advice and the second recommending re-build of the turning joint (which has been done by a Case dealer).
Too bad you are overseas, I would have you call. It sounds to me like there is something crossed somewhere, could very well have been before you got the machine. So here are the next questions. -Has it ever worked properly since you have owned it? -If yes, then were there any repairs made to it before this problem started? You mentioned the problem was present before repairing the turret? -Just to clarify, the service brakes are at the wheels and park brake on the gear box (transmission), correct? -One last thing- at least for this round- Is your drive set as a clutch/declutch on the brake pedal or is the drive pedal seperate so that you have a drive pedal, a throttle pedal and a brake pedal?
Thanks again MTI Mark -Has it ever worked properly since you have owned it? Sadly no and we had it checked, serviced and a trailer brake added by an agent before delivery (which we have taken out of the equation at the moment) -If yes, then were there any repairs made to it before this problem started? You mentioned the problem was present before repairing the turret? I have spoken to the original owners and they assure me that it was working ok. -Just to clarify, the service brakes are at the wheels and park brake on the gear box (transmission), correct? That is correct, the service brakes are at the wheels and the Park brake is a pressure relase setup on the end of the gearbox. -One last thing- at least for this round- Is your drive set as a clutch/declutch on the brake pedal or is the drive pedal seperate so that you have a drive pedal, a throttle pedal and a brake pedal The setup is: Seperate brake pedal Throttle pedal Direction control lever The drawings on the Case site show them as seperate with no connection between the two.
I see you are in the good way,good luck
I should add that there is a travel pedal on this unit.
OK, Sorry for so many questions, but I am putting the pieces of the hydraulic system puzzle together in my mind, so I have another question. -When using your drive pedal to start the machine moving, do you have to operate the throttle pedal seperately, or does it automatically gradually increase with drive pedal actuation? I am referring to what it SHOULD DO as proper operation, not necessarily to what it IS doing, as it may be malfunctioning. The reason I ask is that I have seen equipment that has the "inching" pedal tied into the throttle automatically. I cant remember what the equipment brand or type was though. I found the parts diagrams you were referring to on the web, but only for the crawler excavator, same as you. Do you have the actual model # and serial # off your excavator?
Thanks again According to the operators manual we have, you need to operate the travel pedal and throttle pedal. Some further symptoms (having carried out further tests last night) With direction lever in neutral, operate travel pedal: no movement at wheels but load on engine/hydraulics and hozes seen to flex. With direction lever in forward, a bit of ‘throttle’ applied : press travel pedal to go forwards and wheels seem to slow, press to go rearwards and wheels seem to speed up. With forward selected and ‘throttle’ pressed down, wheels spin at speed but as soon as ‘throttle’ is released wheels stop instantly and transmission appears to be locked (wheel brakes are not on, transmission brake is not on, proved by elimination) As for the parts drawings, check out the europe website as they do list the wheeled unit (I noted the US one did not list the wheeled unit). The machine details are: Case 688 Wheeled, Year 1992, Serial CGG0004073
Sorry Mark, I typed out a reply Friday and apparently forgot to post it before getting interrupted. I tried looking on the Europe website and was not allowed access. Perhaps a direct link to the hydraulic component page would work?? "With direction lever in neutral, operate travel pedal: no movement at wheels but load on engine/hydraulics and hozes seen to flex." Depending on how the system is set up, this may normal. I assume by the sounds of your description, the system uses adirectional valve that reverses flow to the drive motor. Probably in neutral, the valve blocks oil flow to the drive motor, but you are still flowing oil through the travel pedal. "With direction lever in forward, a bit of ‘throttle’ applied : press travel pedal to go forwards and wheels seem to slow, press to go rearwards and wheels seem to speed up." This could be due to directional valve leakby, or limited travel. Does your forward/reverse lever attach to the transmission or a hydraulic valve between the travel pedal and drive motor? "With forward selected and ‘throttle’ pressed down, wheels spin at speed but as soon as ‘throttle’ is released wheels stop instantly and transmission appears to be locked (wheel brakes are not on, transmission brake is not on, proved by elimination)" Does it do the same thing in reverse? Is this turning without using the travel pedal? Is the unit sitting on the ground when you are "testing" it, so that there is some rolling restistance, or is the unit blocked up off the ground?
Thanks Mark The website requires that you register to get a login, here is a pic of the travel pedal circuit. "With direction lever in neutral, operate travel pedal: no movement at wheels but load on engine/hydraulics and hozes seen to flex." Depending on how the system is set up, this may normal. I assume by the sounds of your description, the system uses adirectional valve that reverses flow to the drive motor. Probably in neutral, the valve blocks oil flow to the drive motor, but you are still flowing oil through the travel pedal. Ok, thanks, the circuit does infer (from the parts drawings) that this is the case. "With direction lever in forward, a bit of ‘throttle’ applied : press travel pedal to go forwards and wheels seem to slow, press to go rearwards and wheels seem to speed up." This could be due to directional valve leakby, or limited travel. Does your forward/reverse lever attach to the transmission or a hydraulic valve between the travel pedal and drive motor? It attaches to a direction control valve on the underside (via ports 4 and 5 of the rotary) Does it do the same thing in reverse? Is this turning without using the travel pedal? Is the unit sitting on the ground when you are "testing" it, so that there is some rolling restistance, or is the unit blocked up off the ground? The unit has the wheels off the ground (which allows us to check if the wheels are locked) It does the same in forward and reverse and also when moving
"With forward selected and ‘throttle’ pressed down, wheels spin at speed but as soon as ‘throttle’ is released wheels stop instantly and transmission appears to be locked (wheel brakes are not on, transmission brake is not on, proved by elimination)" I assume you have the travel pedal pressed when doing this. As you let off the throttle, this slows pump rotation, therefore oil flow. I am guessing the the pump should put out enough flow and pressure at idle to move the wheels (with them being off the ground), with the travel pedal actuated. If the pump is not flowing sufficient oil, or at too low pressure, then the wheels could stop at idle. Keep in mind when trying by hand to spin the wheels, that you are trying to spin the hydraulic drive motor through gears opposite of the reduction through the gearbox. Hydraulic motors do not turn very easily with oil, in addition you have a drivetrain full of drag from bearings, to brakes, even though they are not engaged. I would not be concerned that you cant turn the wheels. However you may want to do a flow and pressure test on the pump. Any equipment I have seen that uses a travel or inching pedal should move the machine at idle, sitting on level ground. This machine could be different, but I doubt it. I am searching for a hydraulic schematic. I am still puzzled why your machine would speed up while applying the brakes while in reverse. As you originally asked, there may be some point that the drive and brake systems are connected. I will do some research to see if I can come up with something.
I have tried to find any hydraulic schematic for a wheeled excavator to no avail. Unfortunately the only excavators I have ever worked on were Gradalls, which use air brakes and a regular over the road transmission. Not even remotely similar to your machine. Some mining machines I am familiar with that had a hydrastatic drive system, used integral braking. However it was controlled with a single joystick, as you increased joystick travel, it increased pressure and flow to the drive motors. I cant remember the exact hydraulic configuration, but the machine would not move on a decline with the joystick in neutral. The brakes may very well have been tied into the circuit to release as the drive pressure increases, but this would require spring applied, hydraulic release brakes, which you do not have. The hydraulic drive motor(s) would provide effective braking with both hoses blocked off by a valve also. In your case, you said you have hydraulic applied wheel brakes, which indicates your drive system SHOULD be seperate from your pedal braking system, with no ties. It is possible however that there may be common manifold or valve, that IF something cracked or leaked by could possibly allow brake pressure into the drive system, causing your wheels to drive. But without an actual hydraulic schematic, or being able to physically trace the hoses from each component, there is no way I can tell for definite. Sorry, I was hoping to be able to relate your system with something I am familiar with. My recommendation at this point would be to draw a diagram as you trace out the hoses and components. Something may present itself if you get it all on one piece of paper. Look for any place that the brake circuit hoses have a common tie into the drive circuit, and start there. Many times hydraulic valves have a stamped circuit diagram on them which will give you fluid travel through each valve. I wish I could have answered all of your questions. I hope that I have at least provided a little useful information. Should you come up with a hydraulic schematic and still need guidance, feel free to PM me. After rereading your posts, you mentioned that you had Case technicians working on it. Do they not have a hydraulic schematic to share with you? I would think they would share the info with a paying customer. I cant believe a Case dealer does not have the schematic, or access to it.
Ok, its been a while since I posted so I thought I would post an update on the findings so far. The brake issue has been solved. The cause was a set of inorrectly connected hydraulic hoses which we can only infer were messed with when a trailer brake setup had been fitted before we obtained the machine. The high/low gear issue is not fully resolved as yet. We are now at the stage where we understand the hydraulic circuit which operates a valve in the gearbox. This is actuated by a pair of electro hydraulic valves in what we in the electrical buisness would term, a H bridge type arrangement. Having fitted test lamps to the electrical feeds to these, one of them is not receiving a feed and hence the issue (manualy operating the valves allows selection of the high/low ranges and hence proves the hydraulic circuit is good). So its now into the cab to trace wires and check out the associated relays and switches.