Case Draft o Matic Diagnosis

[Music] hydraulics play a major role in the operation of agricultural implements the case draft-o-matic system aids the farmer in the efficient operation of the tractor and implement the draptomatix contribution simply isn't realized until you hear the customer complaint the draft-o-matic doesn't work to ensure minimum customer downtime knowledge in troubleshooting the draft-o-matic system is required so let's break our system down into the five most common areas of customer complaints and then for each of these five areas you'll see how to isolate a particular problem and where to obtain detailed repair instructions now the first area of customer complaint is the draft-o-matic raises and lowers the hitch arms but doesn't sense enough the next is the hitch arms come all the way up and won't cancel another is the hitch arms hiccup when the engine is running or leak down when the engine isn't running still another is the hitch arms won't raise at all and the last area of customer complaint is the hitch arms won't lower now let's take a closer look at each of these five situations the draft-o-matic system doesn't sense enough well remember the hitch arms will raise and lower the problem is the draft sensing does not work in this case the implement load will not be sensed and there will be no transfer of weight to the rear wheels the result will be either a loss of traction or the engine will lug down if the tractor has been overweighted before you can determine where your problem lies there are some things that you and your customer must check to be sure the draft-o-matic can work the way it was designed to first does the operator know how to properly operate the system videotape vtr 4001 draftamatic operation explains proper operation is the tire pressure correct are the hitch arms set to the right height is the tractor weighted properly all of these are explained in vtr 4001. according to vtr 4001 the rear wheels are properly weighted for draft-dramatic field operation when they have a no slip b three to five percent slip c eight to twelve percent slip write down your answer once you have established that the system is being operated properly you are ready to test the system now to do this you'll need a test fixture there are two different size test fixtures that can be constructed the smaller of the two is used on 770 through 1175 tractors and the larger on 1270 through 1570 tractors the specifications for constructing your particular fixture can be found in the draft-o-matic section of the appropriate service manual for the 770-1175 the fixture is found at the back of section 45 and for the 1270 through 1570 look in the back of section 4017 the 17 and a half ton o watana ram and accessories are available through service tools you will also have to install a zero through three thousand psi pressure gauge in place of the original ton calibrated gauge the gauge is available through service tools also all of our testing will be done with this seventeen and a half ton oatana ram the use of any other ram will require a conversion factor the conversion factor an example can be found in the 970 through 1070 service manual section 45 page 24 the first step in checking the draft-o-matic system is to lower the hitch arms then place the draft sensing lever in the maximum sensing position which is towards the rear then start the engine and pull back on the draptomatic lever until the hitch arms just begin to raise at the instant this raising occurs the draptomatic lever should be near the mid position between full rays and full lower then slowly pull the draptomatic lever to the rear the hand lever should be at the full raised position just as the hitch is at full raise if this is the case it is an indication that the control linkage is correctly adjusted if the draptomatic lever is too far forward or the hitch arms are at full rays before the control lever is at the rear of its travel adjust the length of the control cable on the 770 through 1175 the cable adjustment is made of the cover on top of the rock shaft housing the adjustment for the 1270 to 1570 is made at the control box under the transmission the details for making this adjustment will be found in the draptomatic section of your service manual the next step is to check the pounds of pull required to operate the draftomatic system a general rule of thumb to follow is that it takes approximately 200 pounds of pull greater than draft spring preload to activate the draptomatic system thus the 770 through 1175 which has a 300 to 500 pound spring preload will require 500 to 700 pounds pull to activate the draptomatic the 1270 through 1570 has a 1300 to 1500 pound spring preload requiring about 1500 to 1700 pounds of pull to activate the draft-o-matic to measure the pounds of pull required to operate the draft-o-matic it will be necessary to convert the pounds of pull to pounds per square inch so it can be read on a hydraulic pressure gauge remember these conversions are only for the seventeen and a half ton owatana ram the conversion for the 770 through 1175 is 140 to 200 psi this means 140 psi on the gauge will equal 500 pounds pull the 1270 through 1570 converts to 425 through 500 psi that means 425 psi on the gauge will equal 1500 pounds pull in our testing we're using the 770 through 1175 models so with the engine running lower the hitch arms and check that the draft sensing lever is in the maximum sensing position then slowly pull the lever back until the hitch just moves upward now use the test fixture to pull the sensing shaft to the rear the draft pneumatic should sense somewhere between the 140 to 200 psi reading on the pressure gauge if the hitch arms rise slightly and stop use the test fixture to again increase the draft spring tension the hitch arm should again rise slightly and stop increase the pressure rise and stop increase the pressure rise and stop now release the pressure the hitch arms should lower this is how the draptometic system should operate now let's see what must be done if the system did not operate correctly first if the hitch arms raised below 140 psi the draft springs tension is not great enough on the 770 through 1175 tractors this adjustment is made with the cams at the front of the springs there is a cam for each spring on the 1270 to 1570 the spring tension is adjusted with the center set screw and three lock bolts second if more than 200 psi was required to raise the hitch arms or they did not raise it all either the draft spring preload is too great or the sensing linkage will require adjustment we can isolate the draft spring preload problem from the sensing linkage problem by measuring the gap between the sensing cross shaft and the drawbar bracket with 200 psi applied to the cross shaft the gap should measure two thousandths to four thousandths of an inch if the gap measurement does not fall between two thousands and four thousandths the spring tension must be adjusted if the gap measures between two thousands and four thousands the problem is in the sensing linkage details on all these adjustments will be found in your service manual draft-o-matic if sections an occasional 770-1175 tractor you should find that the adjustment cam on the draft spring does not provide enough adjustment range a new can and washer is available and due to the whole relocation provides one-third more adjustment the cam number is a147468 and the washer number is a147637 so remember if the hitch raises and lowers normally but does not sense the problem is in either the sensing linkage or the draft spring tension now that we've discussed the sensing complaint please answer this question when using the test fixture and applying approximately 200 psi over spring preload the hitch arms should a raised to the top b raise slightly and stop or c raise until the load is released write down your answer the next area of customer complaint we will examine is when the hitch arms raise all the way up but won't cancel in this situation the rock shaft piston bottoms out in its stroke before the mechanical linkage can move the valve spool to the hold position although the hitch arms are as high as they can go the valve continues to direct oil to the rock shaft piston this causes the hydraulic system to constantly run against relief the result is heated hydraulic fluid and possible damage to hydraulic and transmission parts the cause of the problem can be either in the mechanical linkage or the draptomatic valve we will begin by looking at the easiest part first the draft-o-matic valve before the valve cover can be removed to gain access to the internal valve parts the hitch arms must be lowered or you will have oil gushing out around the cover as the arms come down now examine the trigger poppet valve located in the control valve of all draft dramatic tractors foreign material sometimes causes the poppet valve to become stuck in the up position remove and clean the poppet valve assembly your service manual will cover the reassembly then make sure that the piston can travel freely in the valve body after you have cleaned and reassembled the trigger poppet valve recheck the hitch arms if the hitch arm still won't cancel then a linkage problem exists on the 770 through 1175 check the valve spool lockout lever may be broken or need to be adjusted on the 1270 through 1570 you must drain the oil from the draft control housing before you remove the cover a word of caution it could be hot about one gallon of oil will be retained in the housing the eccentric pivot nut located inside the linkage box is used to adjust the valve lockout mechanism details of these adjustments are covered in your service manual draptomatic section also check the adjustment of the follow-up linkage the follow-up linkage on the 770-1175 is located under the cover on top of the rock shaft housing on 1270 through 1570 the linkage is located inside the transmission case remember if the hitch arms won't cancel check the easiest first the valve if the trigger puppet is not stuck check the canceling or follow-up linkage now that you have reviewed the canceling problem please answer this question if the hitch arms won't cancel the problem can be in the a sensing cable adjustment or c spring preload adjustment write down your answer the third area of customer complaint is that the hitch arms either jerk or hiccup when the engine is running or lower by themselves when the engine isn't running the first thing to do is to determine whether the problem is located in the draptomatic control valve or in the rock shaft cylinder to isolate the problem raise the hitch arms to the full raise position make sure that the sensing lever is in the maximum sensing position which is towards the rear now block up the hitch arms in this full raised position then turn off the engine again make sure those hitch arms are well blocked or you can have oil squirting all over when you isolate the control valve in the next step be careful isolating the draptomatic control valve will keep oil from returning to the valve from the rock shaft cylinder although similar in appearance the through 1175 model control valves have a different isolation process than the 1270 through 1570 model control valves on the 770 through 1175 models the control valve mounting bolts are loosened and steel shim stock is slipped under the valve this will block the load check ball hole which in turn will prevent oil flow returning from the rock shaft cylinder re-tighten the valve mounting bolts the isolation of the control valve on the 1270 through 1570 is accomplished by disconnecting and capping the external line from the cylinder to the valve and now that we have isolated the valve the rest of the diagnostic procedure will be the same for all tractors first remove the blocks from under the hitch arms and observe if the hitch arms remain raised the problem is located in the control valve if the hitch arms lower the problem is in the rock shaft cylinder so let's start by examining the rock shaft cylinder and piston for scoring and fractures replace any damaged parts as well as the piston wear rings and seals once again consult the draft-o-matic section of the appropriate service manual for details if the problem was traced to the control valve first replace the blocking under the hitch arms then either reconnect the line to the rock shaft cylinders or remove the shim stock from behind the valve next check the control spool movement is outlined in your service manual the chart found in your 1270-1370 service manual will be helpful in making this adjustment while adjusting the control spool movement inspect the lowering piston seat for chipping if the seat is damaged the draptomatic valve will have to be replaced next examine the load check ball and seat for chipping and cracking to replace the seat it will be first necessary to tap the damaged seat for a removal if internal damage is the case the control valve body must be replaced no amount of tests or adjustments can rectify a faulty valve body now reinstall the ball for the lowering piston into the valve body then the lowering piston and then the spring now install the load check ball and spring and be sure to replace all o-rings in the valve body if all previous adjustments and replacements are performed according to the service manual and there is no evidence of internal valve damage the original problem of lowering or hiccuping hitch arms will be eliminated now that we have completed our discussion on the leak down hiccup complaint please answer this question if the hitch arms leak down the problem can be a spool lockout lever b damaged relief valve or c chipped lowering piston seat write down your answer another area of complaint could be that the hitch arms won't raise at all begin your diagnosis by determining whether the problem is in the main hydraulic system or in the draptomatic valve check the remote valve operation to see if they operate normally if the remote valves do not operate in the normal manner you'll have to use a flow meter and check the entire hydraulic system as outlined in your service manual if the remote valves are operating in a normal manner the problem then is in the draft-o-matic system so the first area to examine is the control cables make sure that they are connected and adjusted properly now if the hitch arm still won't raise after the cable adjustment remove the trigger poppet valve assembly from the draptomatic control valve take this assembly apart and thoroughly clean each component after thoroughly cleaning the valve assembly reassemble the trigger pocket seat the needle valve and then back out two turns install the locking screw making sure that the needle valve does not turn while turning in the locking screw the dome side of the plug goes out then install the spring and spring retainer next remove and inspect the lowering piston assembly make sure the lowering piston is clean and will work freely in the valve body your service manual draptomatic section will provide the details of the reassembly and adjustment of the draft-o-matic valve if the hitch arms won't raise after the cable and valve adjustments inspect the rock shaft piston and cylinder assembly as a quick review if the hitch arms won't raise first determine if the remotes work if they do the problem lies in the draptomatic system if they don't the complete hydraulic system will have to be flow tested to isolate pump or valve problems this completes our discussion on the won't raise complaint so please answer this question when the hitch arms won't raise you should check a sensing cable adjustment b trigger poppet adjustment or c spring preload adjustment write down your answer the fifth and last area of customer complaint that we'll discuss is the hitch arms won't lower let's begin our diagnosis by examining the control cables make sure all of the cables are connected and adjusted correctly once the cables are adjusted observe the control spool the spool must be pulled into the valve body when the draft-o-matic lever is moved to the lowering position if it is not it is an indication that the control linkage is broken or disconnected if the arm still will not lower the problem is either in the rock shaft or the draptomatic valve to isolate the problem block up the hitch arms remember block them securely because we're going to remove the valve cover be careful now remove the spring from the lowering piston and then remove the lowering piston assembly and the ball the cover back on the valve without the lowering piston in the valve then remove the blocking from the hitch arms if the arms still will not lower the problem is in the rock shaft assembly probably a scored or stuck piston if the arms did lower the problem is in the draft-o-matic valve lowering piston the procedure for checking the lowering piston is the same as we did for the hiccups this means cleaning and adjusting the screw as described in your service manual draftmatic section now remember when the hitch arms won't lower check the control cable and linkage if the problem is not corrected remove the lowering piston to isolate the draptomatic valve from the rock shaft cylinder now that you have reviewed the won't lower problem please answer this question if the hitch arms don't lower the first step is to block up the arms and a remove the lowering piston b isolate the dom valve and rock shaft or c check the control cables and spool movement write down your answer for each of the five preceding customer complaint situations the case service manual contains valuable information on all of the various inspections and adjustments when used in conjunction with this diagnostic system any draft-dramatic problem can be accurately isolated and confidently solved

Channel: Benjamin Fitz

Views: 144

Rating: 5 out of 5

Keywords: J.I. Case, Case Tractor, Draft-o-Matic, Tractor Service

Id: aarV6TPZLRo

Length: 24min 34sec (1474 seconds)

Published: Fri Feb 12 2021