Komatsu D31

KWood255 · February 03, 2024, 09:10:13 PM

New project around the farm/sawmill....found an old Komatsu D31A with a 6 way blade. Pretty good shape considering it's age but has been sitting for years.

It need its share of TLC but was able to drive it into my shop, but without steering. The bulk of the issues have been resolved, but still need to fine tune the steering clutches/brakes.

mike_belben · February 04, 2024, 12:31:43 AM

I have a d31P and know them pretty well. Pull your floorboards and battery pan and post a pic, i will know right away if its the same.

A description of what it does or doesnt do would help troubleshoot it

KWood255 · February 04, 2024, 07:25:05 AM

Quote from: mike_belben on February 04, 2024, 12:31:43 AMI have a d31P and know them pretty well. Pull your floorboards and battery pan and post a pic, i will know right away if its the same.

A description of what it does or doesnt do would help troubleshoot it

Thanks Mike!
This machine had been sitting for at least 6 years without running. When I picked it up, it started pretty easy and would move forward/backwards but had no steering at all.

Left side brake band was out of adjustment, and the right was worse. I could put the pedal to the floor without resistance.

Both steering clutches were not working. While troubleshooting I cracked open the hydraulic hoses that feed the clutch calliper/slave cylinders. I had essentially zero oil when pushing the pedal or not. I then cracked open the pressure and return hoses from the transmission which feed the steering valve. I had ample supply, but zero return. This sent me to the steering valve.

On full throttle I opened the pressure side hose, which seemed fine. Initially when I opened the hose feeding the left clutch I had very little, until all of a sudden if released. Almost seemed to be air locked for a second. Once the hoses were back in place, I began to have steering.

I did notice that when I turn, it lugs the engine slightly. I do not know if this is normal, or maybe the clutch is not releasing fully. When under load, the left will spin while the right track stops. Upon pushing left brake, the right track will start again. Almost like a limited slip differential.

I feel the steering valve is to blame and will disassemble/inspect/clean today. The right pedal hangs about 1.5" lower then the left, so I'm curious if the steering valve is slightly left of centre, causing some right side clutch input.

Did I mention it needs a bath?

GRANITEstateMP · February 04, 2024, 08:54:52 AM

Whenever I give something a bath, it just reveals more problems :-\. It does make things much nicer to work on

newoodguy78 · February 04, 2024, 09:03:22 AM

GRANITE that made me laugh. Every time I think I'm caught up fixing I'll start washing stuff and the cycle starts all over again.

mike_belben · February 05, 2024, 02:35:01 PM

I see some similarities but the steering is totally different than mine so i dont wanna lead you astray. I will say i have had steer issues that resolved themself while chasing things down. Which i believe indicated air locking in the various circuits. The pump sends oil to the modulator valve which regulates relief pressure to around 300psi with a slow soft ramp up between shifts. From there my oil goes to the steering valve at the back with linkages to move the spools. Then its hardpiped into slave cylinders that when the pedal is pushed opens a path for the slave to extend against a yoke which pushes a diaphragm to uncouple a typical friction clutch. So hydraulic actuation first disengages the track drive power and the a little more stroke mechanically pulls a brake band to sharpen the turn.

But again yours looks totally different. Is it hand steer? Mine is full of linkage rods, yokes and pins and rockers and cam followers that all wear and contribute to erratic steer performance.

Biggest thing is dont operate it if youre driving thru the brakes. If ya gotta stomp to get it to turn theres an issue.

If you put it in neutral, push the pedal down hard then go into gear to make a turn it usually works a bit better. Thats how mine was for a long time but i finally have it working pretty easy effort wise.

KWood255 · February 05, 2024, 03:00:30 PM

Thanks again for your reply Mike. I seemed to have either an air lock or obstruction as well. I took the steering valve apart to clean, and didn't see anything wrong. After reassembling and tuning up the linkages, it's working about perfectly now. I am really impressed. The only other thing is that my 6 way doesn't want to tilt to the left. It tilts right, and comes back to about centre, but won't tilt left. The hydraulic cylinder appears to have plenty of travel remaining and I can't find anything holding it back mechanically.

Wlmedley · February 05, 2024, 05:21:10 PM

Sounds like your transmission pump was airlocked.Probably from setting so long but if it does it again I would suspect bad shaft seal on your transmission pump which will cause it to suck air instead of oil.Common problem on older Komatsu dozers.

Wlmedley · February 05, 2024, 06:02:12 PM

When tilting blade to the right is cylinder extending or retracting?

mike_belben · February 06, 2024, 07:52:43 AM

Crack the lines with a pan underneath and have someone stroke the valve spool left and right. See if it has oil flow from the hoses in each direction.

If so consider it airbound. I would pull the cylinder at each end, lay it down and cycle it while tilting to put the ports up high so the air can get out the hose and back to tank.

I just had that cylinder off last night for port modifications from breaking a fitting off.

If the trans oil is perpetually frothy after running that would suggest sucking air. If the tranny cooler lines are rotted or broken in the 6" of belly pan mud like mine were the trans wont work right either. The oil may hardly come out until mud totally saturates.

moodnacreek · February 06, 2024, 01:23:08 PM

Always consider a blown piston seal, that has confused me a few times [it doesn't take much]. Last summer I thought I had this on a front end loader but someone crossed lines. Funny how it would almost work.

mike_belben · February 06, 2024, 06:20:17 PM

Mine extends to tilt right. Im thinking the rod shaft may have backed the nut off.

Wlmedley · February 06, 2024, 06:47:11 PM

Mike, I agree or packing gone.

Wlmedley · February 06, 2024, 08:12:23 PM

Wanted to add before I forget that if either track quits pulling under load when not steering you have a problem. There should be two 1/8" pipe plugs somewhere on back of steering valve where you can check steering clutch release pressure. If steering clutch slips without pressure you have clutch problems. Clutches are spring applied ,oil released.Hope this helps.

mike_belben · February 06, 2024, 10:18:45 PM

Quote from: Wlmedley on February 06, 2024, 06:47:11 PMMike, I agree or packing gone.

I was thinking that but with cylinder removed i can tip my blade from one side to the other with one hand so even without a piston seal i kinda expect it to tilt. Hopefully the rod thread hasnt tore off.

KWood255 · February 09, 2024, 09:15:37 AM

I pulled the cylinder off yesterday, and it seems fine. While disconnected from the linkage, the ram has full travel. What we noticed is the linkage rod controlling the tilt function has been broken and repaired before. It seems to me that the linkage rod is about 4" too short, so it will not allow ot to tilt left. I'm only guessing it was bent at one time and instead of replacing, someone shortened and welded it back together, or replaced it with a part from a different machine. When the linkage was removed, the blade tilts left and right easily, and the cylinder travels full distance. I can't see any other explanation.

My job today is to weld in a 4" extension to the rod. This will confirm our suspicions, or send me down a new path of head scratching.

mike_belben · February 09, 2024, 09:19:19 AM

Sounds odd. Do you know how to post pics here? If not send me some to mike_belben@yahoo.com. im wondering what this linkage rod even is. Mine is mounted between tabs at each end.

With the cylinder hanging freely does it stroke to its limits by the hydraulic control valve?

mike_belben · February 09, 2024, 09:25:17 AM

Theres a pretty clear view of what it should look like in this vid at about 2 minute mark. Dont mind the solenoid solector valve and that my tilt cylinder body is flipped so the ports face up at the selector.

https://youtu.be/-7pOgg077l4?si=dMO4i68lv-4IR970

KWood255 · February 09, 2024, 03:33:01 PM

Thanks Mike, my assembly looks different then your, in fact the mounts for the rod appears to be rotated from factory by 90*. I will try to add a picture.

mike_belben · February 10, 2024, 12:28:15 PM

Oh yeah totally different. I know mine had the blade break off when it was flipped off a steel trailer ramp and theres quite a bit of fabwork to fix that. My blade is also reskinned and its got a 4 bolt cat d4 trunion ball welded on now which i had to weld back up. Theres no tellin how many hours but i bet its 20k.

Your trunion system is completely different.