It started while I was operating it in reverse and when I crossed over neutral the parking brake engaged before I got it into forward… (I was actually looking at the dash and saw the light come on at that moment) after that I tried cycling the parking brake and nothing happens? First thought was maybe the switch is bad, replaced it and nothing changed. so I checked the diagnostic codes via the flashing light indicator and I got codes 255 CID 1699 forward/neutral/reverse and 256 CID 1700 position sensor (steering) both of witch are related to the joystick either getting high/low/intermittent voltage. I checked the battery with a multi meter I borrowed from a friend that wasent really for direct current the only DC option was 300V so I wasent able to get an precise voltage reading.. do I need to get the correct multimeter and make sure the battery and alternator are good before I go replacing the joystick with the controller it sets on?? I only see the light for the battery on the dash when the machine is off and I turn the key once, soon as it starts that light goes away so I don’t know if I still need to be concerned with that or not? Lastly if I do have to replace the joystick will I have to calibrate the new one? Cat wants to charge me $800 just to drive out to me so I’m hoping to avoid that if possible!
Yes. Low output from the alternator is a common cause of electrical/electronic issues on this model. Check the basic stuff such as fan belt condition, tension, etc, while you’re in there. Post a Serial Number. It helps in finding technical information.
Sounds like what I went thru a month or so ago. I think I would advise to check the hyd ports to make sure they have oil PSI to rule out pump coupler. Else for less experienced people they may not know how to go thru and test all the sensors.
are those codes consistent with the pump coupler?? What causes the coupler to fail, do you know?
RKG-prefix D5G. So the earlier comments regarding alternator output are most certainly valid. You should verify the alternator output voltage and everything that might affect it such as fan belt tension, condition, etc, as a first step before you consider doing anything else. The second step (or could be the first if you have the gauge handy) as suggested by Mike is to get it on the test ports and see if there is any pressure. No pressure anywhere - failed drive coupling. See the thread Mike created HERE and how the conclusion was finally arrived at theat the coupling was toast. All the info regarding testing pressures is also there.
I’m happy about the first half of that reply but not the second half….. and the drive coupling gives no warning that it’s about to fail??
Are those codes constant with the drive coupler??
Could be anything TBH. Verify alternator output before moving forward. I'll find some diagnostic procedures for the 1699 & 1700 Component Codes but I would suggest that you don't go digging into them before checking that the machine system voltage is sufficient. As a condition indicator the battery voltage should be around 12.5v with the engine stopped and the alternator should be producing at least 13.5v with it running.
No it does not. In the case of Mike's D5G a lot of time was spent tail-chasing Diagnostic Codes and test procedures when if a pressure gauge is available it's possible to rule out a failed coupling in a few minutes. I was simply suggesting that if you have a pressure gauge it would be an easy test to rule out the possibility.
No signs. Just came to stop and park brake light was on. I didn't realize there was a separate pump that ran the blade. So I thought pump was fine and proceeded to test and change sensors. After that still nothing next test was the hyd port test. No fluid, no psi. Coupler no good. 7800hrs on machine
I'm not trying to cut in on you suggesting how to go about finding a fix. I enjoyed learning the steps to testing. Just time consuming. It was still cheaper then having cat drive out and charge 2k to diagnose. I also could've spent all month doing the coupler and it still would've been cheaper then having Cat do it lol
^^This. G series machines get weird when the voltage drops from weak battery or alternator.
I’m going to get a more accurate multi meter now and I’ll check the voltage in the morning! I see it’s divided on whether to pull the motor or slide the pump back to get the old coupler out and the new one in?? Pros and cons of both methods would be appreciated, even if it’s not the coupler this time the machine has 8500 hrs so I’m sure it’s coming! Thanks you guys have helped a lot
Could you point me in the direction of the pressure gauge I’d need to test the hydraulic ports? I’m headed out to test the alternator and crossing my fingers but if that’s not it I’m gonna need that gauge
Do you have a 500psi pressure gauge.? Hook it up to Test post #7 (should be marked "Park Brake") and with the engine at Low Idle see what the pressure is with the parking brake switch in the OFF position. Try it at High Idle also. Spec is 344 ± 44 psi. If you get pressure with the park brake in the OFF position the pump coupling is OK.
Can you send me a link to the pressure gauge I need?
Cateprillar 8T-0855 (0-600psi) but TBH any gauge with a maximum reading of 5-600psi will do the job. The test procedure calls for a 177-7862 Hose, 2 x 6V-4143 Couplers, and a 6V-3989 fitting to screw into the pressure gauge, but that's using quick couplers at both the machine and gauge ends.
I got the hose made up headed out there now! I had found a thread yesterday or the day before that had guys debating on what was the better route to pull the motor or slide the pump back but I can’t find it again?? You had posted the work over sheet to pull the pump in that thread I think. The majority of guys in my position went for pulling the motor but a cat mechanic commented at the end of the thread and said if it’s a G model you should go for the pump side since there’s enough room to just slide it back and change out the drive coupler. I wanted to try to get in touch with that guy to see if he had any advice or tricks that would be good to know before I tear off into it, if that’s what needs to be done? I’ll know shortly what needs to happen!
I’ve got nothing in any of the test ports
But I checked the the alternator after I checked the test ports and at first it read 13.04v and then it jumped to 14.21v the battery was at 12.02v then jumped to 13.10v so my question is should I have pressure to the parking brake test port no matter what or if the light on the dash isant going off will there not be pressure?
Alternator output sounds OK. I have no idea why it should jump like that. The pressure tests at all those test ports are made with the parking brake released. If the electronics are not giving the signal to release the brakes then it is quite possible that the rest of the hystat system will not function.
Can you send me a diagram of where the parking brake Selniod is at
I'll send you a complete electrical schematic. That shows the wiring as well as component locations. Check your messages.
Welcome, Clear the codes,turn the key on but don’t start it see if it sets 255 again
Thank you guys for all your help! It’s most likely the drive coupler I’m going to pull the pump in the morning. So the dozer belongs to my mothers husband who has taught me everything I know about operating, but he did not trust my mechanicing ability at all (granted I will rig some **** up on my own things to get by, so I have some strikes against me) but we got a cat tech who’s a family friend come out and hook his computer up to it, basically cuz he didn’t trust me and needed a second opinion…. The tech said sounds like you have good help and you might oughta listen to him! So thank you guys, I got some much needed respect outta this whole catastrophe! This was my first time using this forum and I am very impressed at the response times and knowledge people are willing to share! Again thank you!
When we did ours we pulled the engine and left the pump in the machine so you dont have to remove all the lines. I talked to a few cat guys and thats how they do it.
According to the dealer they pulled motor to replace drive coupler. It was a expensive job, 13k $ I probably should've tried to do it myself but didn't really have time
The procedure shown in the service manual is to remove the engine and pump as a unit and split the pump off it once it is out of the machine. There is no procedure just to remove the engine alone. If an experienced technician decided to only remove the engine and leave the pump in situ he's probably the type of guy who has done it before and doesn't need to refer much to a procedure anyway. However for anyone who has not done this before the service manual procedure is probably all they have to go on. My suggestion would be to do it way the book shows because at least you'd have a procedure to work to. This is based on the fact that nobody involved in the job has ever done it before. The difference in weight between just the engine and the engine/pump is not going to be much. Whatever is used for lifting will likely have the capacity to lift either just the engine or the engine/pump.
Im having same issues but drive coupler was fine is there anything else that could cause no pressure at any ports
It's happened before where the hub to which the drive coupling connects has slid away from its position and results in no drive even though everything looks undamaged. Did you investigate that possibility.? Also did you attempt to rotate the pump input shaft.? If you did how hard was it to turn.? What model machine are you working on.? Serial Number.?
Yes everything looked good , and yes I could rotate the hub by hand but it takes a little pressure to make it turn. It’s a cat d3g 2008
That's like saying it's a '08 white Ford F150. Machine Serial Number please. What is the current state of the machine.? Still disassembled.? You literally should need a pipe wrench on the hub to turn it. Where were you testing pressures.? Also did you obtain the list of Diagnostic Codes from the machine electronic control system.?
CATOOD 3GL JMHO 1951 It’s currently put back together to get it home. And yes there is zero pressure at either port other than the auxiliary pump for the blade
Let's get into looking at the electronics, even if only to rule it out. See the attached. Start from Page 4. All you need are a couple of bent paperclips to extract the Codes.
Is there a charge relief valve on the hystat? Could that potentially cause no pressure?
Did you look for Codes yet.? You should really eliminate any possibility of a fault in the electronic side before diving into the hystat system. Attached the hydraulic schematic.
I got code 261
That is for the throttle switch. It needs fixing before proceeding further. The troubleshooting procedure for the code is on Page 172 of the document that I uploaded above. See where that gets you.
Im now getting just 222
From what I read that means no Active codes. So was there something you found that was not okay at the throttle switch. Simon C
See the attached which is the complete System Operation document for the hystat covering both hydraulic and electrical/electronic systems. It will hopefully help you understand a bit more how it works. As per Simon's question. What did you do to get rid of the 261 Blink Code.?
I believe it popped up when I disconnected it and I erased it and never popped back up. So far people telling me it’s gonna be a mechanical problem so I’m gonna take engine and pumps out tmr is there anyway for them to come out together or do I have to take engine out first then pumps?
The engine & pumps are removed together according to the service manual, the. Split apart afterwards. The procedure has been posted somewhere. I’ll see if I can find it. EDIT: See the attached. The special tools listed are not mandatory, they only make the task of removing the assembly easier.
Ok thank you also is there a way to take the sun gear out to get it to roll?
You will need a slide hammer with an adapter that will screw into the thread in the end of the sun gear according to the procedure.
I got the hystat and charge pumps out is there a parts diagram on those? Like how to disassemble the hystat pump to take it apart and put back together
There is. See the attached. I suggest that you should study it carefully and ask yourself do you have both the tools and the required level of technical ability to perform this procedure. There are two identical hystat pumps, one for the left track and the other for the right. For you to have no pressure anywhere this would indicate that likely nothing in the pump stack is turning. So if that is the case, and if the problem is not in the coupling between the engine and the pumps (please post photos. We haven't seen it close up yet) then the focus is that either the input shaft to the hystat pump closest to the engine could be broken, or or maybe the charge pump has failed. Unfortunately there is no D&A procedure for the charge pump. As it is much simpler I suggest that you look at it first to rule it out.