Hello, thanks for considering my question. I have a 1990 Cat D3C Series2 dozer I’m troubleshooting a malfunctioning steering condition. Dozer will not move forward or reverse. No issues before shutting it down. Sat for a month, now will not operate properly. All linkages, brake, and cams have been confirmed as functioning properl. I’m looking into the hydraulic system. What is the hydraulic pump RPM at when the engine is running at idle? My service manual indicates a pump output pressure of 300 psi at 3600 rpm. What does that equate to at idle? Thank you
That is a specification used to bench test the pump off the machine. It cannot be used for diagnostic testing on the machine. Please post a Serial Number so that we can look at the same information you’re looking at.
Thanks for checking into my question. 1PJ00765 is what I’m showing on docs. I’ll be at the machine later this mornin. I’ll be sure to have the sn for future posts. Thank you again.
1PJ00765 is a good Serial Number. Do you have a full copy of the Transmission Testing & Adjusting section of the manual.? First thing that comes to mind on a machine that has sat for a substantial period is an air leak in the suction side of the transmission pump causing it not to prime.
It appears to be there. I have both the Service and Parts manuals. The condition of the machine as follows: Purchased used @ aprox 5200 hours 4 months ago. <2 hours use since purchase, ran fine, no issues whatsoever. After sitting for one month went to use and found it will not move forward or reverse normally. Minimal movement when applying left hand control. Actions taken: Parking brake inspected at cab controls. Hyd oil full, clean, no burned smell. Changed hyd filter Inspected linkage from hand control to valve, no apparent wear. Bled top of filter can by loosening plug with engine running. Added three quarts oil to the bevel gear. My next troubleshooting steps was to investigate the hydraulic oil circuit. Found the hyd circuit diagram in the manual, seeking a description of expected pressures at given points. Other ideas are greatly appreciated! Thank yo.
They are all in the T&A section of the service manual. That’s why I asked if you had it. Is your manual a genuine factory one.? Attached is the T&A from the OEM service manual. TBH if the machine worked fine before it was parked I would be looking very closely for an air leak at the pump suction where it pulls the oil from the transmission case. A couple of time you have use the expression "Hyd oil/hydraulic circuit" but this is the transmission circuit. Do you mean the power train oil.? To me "hydraulic" means the implement (blade/ripper) system.
Thank you. Yes both manuals are original Cat manuals. Also yes the transmission circuit. First dozer I’ve owned so on a steep learning curve. Farm and equipment all my life, never worked on a dozer. I will start with pump as you recommended. Thought it was odd it was running fine, parked, then it wasn’t…. Thanks so much, appreciate your feedback and time.
Thank you for the T&A document it will be very helpful! I didn‘t see this in the books I have.
The T&A document is a “one size fits all” for both direct drive and powershift transmissions. You’ll need to find the section in it that applies to your particular transmissions type.
Good day. I checked the pump out as you recommended. No issues observed. I moved onto the right clutch and brake. It appears moisture in the housing caused the pad to bind to the drum. While inside the case I observed a backed off bolt on the end of the clutch cylinder shaft, not the yoke stop. But also the spring item 38 on the steering clutch linkage. QUESTION should the spring be under tension when the associated linkage is removed? QUESTION From my photo does anything appear out of the ordinary besides the spot surface rust? Thank you. Bill 503-550-0898 Newberg Oregon
Another question. What is item 32 for from the steering clutches and brakes section page 118.01 of the service manual. In a relaxed state the assembly is loose and the spring is slack. Is this normal?
I must admit to being somewhat perplexed. In your OP you said....... I'm still trying to understand why you are messing around with the steering if it won't move in either direction. Attached is the System Operation section of the service manual for the Power Train and steering systems. Seeing as you didn't have the Test & Adjust section I'm assuming you don't have this either.
Thank you for the docs. I switched directions after a service truck mechanic stopped and gave me a few minutes from his booked schedule. Based on the fractional at best movement he felt the brakes were likely adhered to the drum recommending I run the dozer and ”rock” it back and forth. After doing as he suggested the left track began to move about 4”, the right tracks never moved. When I pull the lid on the right side to inspect the brake the band were indeed stuck to the drum. Crows foot broke it free. Like I eluded to before, this IS my first rodeo... Thanks again for your advice and time.
Dozer update. pulled cover on right rear brake and clutch, brake band stuck to drum. Dislodged band from drum, reassembled and the machine moves fine without issue. Thanks to all for their assistance and advice.
I have seen multiple posts on various forums over many years, where someone with a D3 or 931 couldn't get it to move, after it had sat for a while. Despite many discussions, opinions and responses, I have never previously seen a single original poster come back to their thread, and advise what was causing the problem - nor anyone coming forward with the exact solution. It seems obvious to me with the largest percentage of steering clutches and brakes on D3's and 931's being dry - that corrosion, caused by moisture ingress to the steering clutch compartments - has caused the brake bands to stick to steering clutch drums, and thus stopped the tractors from moving. I'm guessing that all the posters with this problem were too embarrassed to post their findings on the threads they started, when they discovered their problem was simply brakes stuck to the drums. I've had exactly the same problem with my 931B, although it sat abandoned for many years, and corrosion destroyed the breather assembly on the cover over the bevel gear compartment - thus letting some moisture into that compartment. I have yet to find if there are any breathers for the steering clutch compartments. I cannot find any in the parts book, so I'm wondering if the bevel gear compartment breather is supposed to suffice for the steering clutch compartments, too? I'm guessing there's openings at the top of the plates between the steering clutch compartments and bevel gear compartment - but I've haven't pulled any of the covers yet, as I'm still working on the engine and transmission, and I don't want to get ahead of myself.
Thanks for your note. The brake/clutch compartments are pretty much sealed, gaskets on lids and linkage components. The bands appeared to be stuck completely around the drum. A crows foot prybar was all it took to free it. my neighbor, a former North slope equipment mechanic said sometimes they’d have lift their tracked machines up to get them to free up. I’m assuming it was ice and rust. If it happens again, that’s what I’ll try first!
Thanks Venturahandyman, I think I'm going to modify my 931B steering clutch compartments and add breathers to them. Can't be too hard to fit one each side, it looks like Cat cheaped out on the design there. Every other Cat I've ever owned or worked on, had breathers for every compartment. I think I might go for some of the 4H6112 or 1F8488, older style, more durable breathers, too. The standard D3/931 breather isn't exactly the most durable thing I've seen.
Good idea and thank you for the parts numbers.
Cat improved the steering clutch compartments by adding a corrosion inhibitor and sealed the cases from the factory. After much searching I came across that nitrogen prevents corrosion so my best educated guess is Cat filled the compartments with nitrogen gas and then sealed them. It's listed in a pamphlet I got from Finning on the improved 931B. I try not to drive in water and since I put up a pole shed I rarely leave the machine outdoors. One of the brake band support bolts on the bottom was almost completely rusted off. Thankfully the threads in the case were OK and I could get it out to replace it.