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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 1148
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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12G Motor grader wont move, also the entire hydraulic

Customer Question

12G Motor grader wont move, also the entire hydraulic systems wont work
Submitted: 2 years ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 2 years ago.
Hello,Can you tell me more about this problem?Theses two systems are completely independent of each other. They share nothing beyond the fact the engine drives them. The hydraulic pump is driven by the front of the engine and the transmission is driven by the rear.Please include the machine's full serial number with your reply.
Customer: replied 2 years ago.
the serial number for the machine is 61M6314. The machine attempts to move but it wont budge. you can not even lift up the blade, we have removed the parking brake as it uses air.
Expert:  catmastertech replied 2 years ago.
Have you checked the transmission filter?Does the transmission oil smell burnt?
Customer: replied 2 years ago.
we have not checked the transmission as we can not determine the exact cause. the entire hydraulic system does not work. the blades will not lift or even tilt. we have checked the main hydraulic pump and pilot pump and everything seems ok. we have tried leaving the machine to run on idle and loosening the hoses to get some air out but that still does not seem to help lift up the blade from the ground.
Expert:  catmastertech replied 2 years ago.
Check the transmission filter for debris or burnt smell.If you find anything, drain the transmission oil and check the suction screens for more debris or metal. For the hydraulic system see if the pressure release valve is stuck down. This is the small rod sticking out of the floor by your left heel.
Customer: replied 2 years ago.
ok, ill check on that and reply soon as possible. my left heel while sitting inside operators seat correct?
Expert:  catmastertech replied 2 years ago.
Does the transmission shifter return to neutral correctly?
Expert:  catmastertech replied 2 years ago.
Yes, when in the seat.
Customer: replied 2 years ago.
yes it returns normally, when you select a speed, you can feel the change.
Expert:  catmastertech replied 2 years ago.
Does the steering work normally?
Customer: replied 2 years ago.
no, the machine does not move. when you turn the steer the tires do not move. its locked in place.
Customer: replied 2 years ago.
this just happend overnight after we parked the machine from a 1 week job
Expert:  catmastertech replied 2 years ago.
Here is a list of possible drivetrain issues. Check List During Operation TransmissionPROBLEM: Transmission does not operate in any speed or does not engage (slips) in all speeds.PROBABLE CAUSE:1. Low oil pressure caused by:a. Low oil level.b. Control linkage loose or adjustment not correct.c. Failure of the oil pump or the pump drive.d. Air leaks on inlet side of pump.e. Leakage inside the transmission.f. Adjustment of the modulating relief valve not correct, or valve does not close.g. Load piston not closing.2. Mechanical failure in transmission.3. Failure of the differential or bevel gear.4. Failure of the final drive planetaries.Review these items to see if any are related to your problem.
Customer: replied 2 years ago.
ive seen this in the repair manuel, i need to get the blades off the ground first. i doubt its a transmission issue as it froze when we were using it to clear debris in the yard. it just froze then the driver dropped the blade on the ground to call the mechanic and we have not been able to raise it of the ground since.
Expert:  catmastertech replied 2 years ago.
Do you mean the drive system LOCKED and stopped the machine?
Customer: replied 2 years ago.
im really not sure but something like that yes. the machine stopped moving and the entire hydraulics stopped working. we have been able to get the cylinders to budge but not able to have it lift the blade off the ground
Expert:  catmastertech replied 2 years ago.
I would check the valve under your left heel. It is called UNLOADER valve in the manual. Sometimes it is called Combination valve too. This valve can divert all oil the the hydraulic tank when the unloader rod is pushed down. It is an option for the unloader rod but, the valve should also supply the steering. (If my memory is correct.)
Expert:  catmastertech replied 2 years ago.
The drive stopping as you described could be a failed tandem chain or the differential.Open the chain cases and inspect all four chains to see if any are broken.
Expert:  catmastertech replied 2 years ago.
If you don't find a failed chain, drain the drain the differential housing and check for metal in that compartment.
Customer: replied 2 years ago.
we did have some chain break a couple of weeks back but we replaced it.. we figured it didn't really effect anything. we will do a more thorough search in the morning and seeee, ill let you know the results asap.
Expert:  catmastertech replied 2 years ago.
Ok, I may be away tomorrow during the day but, I am usually around in the evening. I will be looking for your reply then.
Customer: replied 2 years ago.
thank you.
Expert:  catmastertech replied 2 years ago.
You're welcome.
Customer: replied 2 years ago.
hey sorry for the delay reply. i didnt see the rod you mentioned. only the valve under my left heal. we checked the tranny filter and screen, it wad spotless, no debri or signs of wear. is the rod inside the valve? we did not remove the valve but what we did was try to blead the pump and we saw some particles, when we took apart the pump there was no wear but only signs of heat. the mechanic had also explained that on one of the hydraulic oil and filter changes, they didn't screw on some of the hoses tight enough, so the pump took in some excess air from the tank. further ive never noticed it but how do you check the pressure on this machine, i cant seem to locate a valve for it.
Expert:  catmastertech replied 2 years ago.
The unloader rod and valve section was an option and is not installed on all machines. Your valve would still have the pump pressure control and the steering pressure reducing valves.These older machines do not have pressure taps. You must add them were needed for testing.This is all shown in the service manual, Testing and Adjusting, 12G, 130G & 140G MOTOR GRADERS HYDRAULIC SYSTEM AND STEERING. Media Number -REG01576-03.

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