Komatsu D31a-16

[Matthew9621]

I’ve got a weird issue going on with my d31-16. Haven’t owned machine maybe 7 months, sat for around 10 years before I got it. Engine was bad, rebuilt and reinstalled everything running great.

The issue at hand now is that the 6 way blade will tilt way to the left and barely past level to the right. What is odd is that it was doing it the opposite direction. All the way right and barely past level to the left. It changed when I was pushing a fence row and went through a low spot and had blade tilted following the terrain. The rod that connects the tilt cylinder to the blade was bent. I cut out that piece and replaced it with new material that was prior to this new issue. I did lengthen it some because it wouldn’t tilt level. Measured cylinder stroke and lengthen accordingly.

I’ve repacked tilt cylinder thinking it was bypassing inside. No difference. Not sure what else to do next.

Any info helps! Sorry for the long post!

 

[epirbalex]

At the back of the blade down the bottom there is a ball mount for the blade to swivel on . On the inside against the back of the blade there is a clamp , they come lose . Check that . I damaged one and needed to heat it to bend it back to fit properly . This is probably not the issue but needs to be checked first .

 

[Matthew9621]

At the back of the blade down the bottom there is a ball mount for the blade to swivel on . On the inside against the back of the blade there is a clamp , they come lose . Check that . I damaged one and needed to heat it to bend it back to fit properly . This is probably not the issue but needs to be checked first .

I checked it this morning it still looks good.

 

[epirbalex]

If there is no worn out mounts for the tilt ram and the main swivel mount for the blade , no cracks to welds to the mount that stands up on the c-frame that the rod connects to the back of the blade check to see if the ram is extending fully and staying fully extended and when its contracted to .If the ram won't hold could be an o-ring in the hydraulic control valve . It would be better for the rod you extended to be factory length . What are the main C-frame mounts like where it mounts to the track frames . Can you post some pictures , I'd like to know if the blade is the same as the one I've used

 

[Matthew9621]

Sure I can post pictures this evening. I would like to know what the length of the rod is supposed to be from factory.
As far as I can tell the cylinder rod is moving full stroke and not bleeding off. You can pickup front of dozer with the blade tilted and it doesn’t push the cylinder back in.

 

[epirbalex]

There is so little to go wrong with it unless something has been modified , there are two rams listed , neither show their length difference . It could be an incorrect ram used to replace the original .
Rod length not mentioned either , thats a pretty heavy bit of kit to bend if its the rod I've seen .

 

[Matthew9621]

It’s a piece of 2” steel. I was surprised the old one was bent. I’m beginning to think it’s the problem. But what I don’t understand is what changed like you flipped a switch ?

 

[epirbalex]

Extending the rod would put more tilt down on the left and reduce the right which you have . I would sort the length of that , little bit of extra length would make a big difference at the tip of the blade , all the pins look good so theres no loss of function with them . Has the pitch of the blade changed ?
The force to compression bend a bit short 2 " steel must have been great . There may be damage to track frames or their mounts maybe a twisted C-frame .

 

[Matthew9621]

You’re right about the extending of it, when I did extend it the blade would not level out. It was twisted to the right even with cylinder extended to push blade to the left. I don’t think the pitch of the blade has changed. Whenever I got this machine the blade was off of it due to the engine being pulled. I looked at the c frame when I took pictures everything “looks” straight. No twist or cracks where it pins to the track frame. I’m tempted to shorten the rod, maybe I extended it too much. Maybe I’m overthinking it ?

 

[epirbalex]

Theres been a fair bit of work done to replace the blade pins . On picture 3 it shows movement of the rod along the pin , its not much but the movement by the time its multiplied to get to the blade tip could make some difference , a couple of collars to stop that movement would fix that . Add to that the difference to the rod length may give you enough tilt both ways . There is no room for a longer ram as the body is close to the swivel mount in picture one so thats more than likely the original . Is the swivel fitted the right way around ?

 

[Matthew9621]

I have no clue if it is or not. It was already on the machine when I got it. I guess I could turn it around and try it

 

[Akrider24]

I’m having the same issue with my D31A-16. I keep making adjustments via the valve on the right side of the “C”. I’m thinking that I have a poor seal in one of the angle cylinders that allows too much fluid on one of the ends.
The adjustment process is simple to do.

 

[Matthew9621]

I’m having the same issue with my D31A-16. I keep making adjustments via the valve on the right side of the “C”. I’m thinking that I have a poor seal in one of the angle cylinders that allows too much fluid on one of the ends.
The adjustment process is simple to do. View attachment 308601View attachment 308602

So that’s some good information there, but I’m talking about the tilt cylinder that tilts corner of blade down left or right. What’s odd about mine I was grubbing mesquites and it was cold that day and it was working just fine tilted to each side evenly until it warmed up. I’m thinking I have a valve problem. Since you have the same machine as me the rod that goes from the top
Of the blade to the knuckle it’s shown in picture 3 that I posted. What’s the length from center of the pins ?

 

[Akrider24]

Unfortunately, the center link on mine was broken in pieces and welded back together before I got it. I understand that the blade tilt isn’t working properly but the instructions that are in the pictures are how you make adjustments to the cylinders. The valve is on the right side of the C, it’s a square box with multiple hoses going to it and multiple bleeder screws. The valve itself looks like a large bolt head, I think I use an 1-1/4” wrench to loosen/tighten. Are you able to read the instructions in the pictures?

 

[BMsuper]

Sure I can post pictures this evening. I would like to know what the length of the rod is supposed to be from factory.
As far as I can tell the cylinder rod is moving full stroke and not bleeding off. You can pickup front of dozer with the blade tilted and it doesn’t push the cylinder back in.

I don't know if you have the same tilt rod setup as my 1978 D31A-16. When I bought mine, only a couple of weeks ago the blade would tilt far to the right but only go back to level to the left. I found the Tilt Rod was bent, probably as a result of using a root rake on the blade. I'll try to post a picture. I have the rod removed an am going to try to heat it and bend it back straight. I'll have to let you know how it works out. Good luck with yours.

 

[epirbalex]

I don't know if you have the same tilt rod setup as my 1978 D31A-16. When I bought mine, only a couple of weeks ago the blade would tilt far to the right but only go back to level to the left. I found the Tilt Rod was bent, probably as a result of using a root rake on the blade. I'll try to post a picture. I have the rod removed an am going to try to heat it and bend it back straight. I'll have to let you know how it works out. Good luck with yours.

It looks more likely that tilting too far to the right caused the bending of the rod . Is the blade fully tilted to the right in that picture ?

 

[BMsuper]

No, I tilted the blade to the right to align the tilt cylinder with the opening where you would be able to drive the pin out holding the tilt cylinder in. It was blocked in that position in case I needed to remove the tilt cylinder. I now have the tilt cylinder rod out and I am going to heat it and try to bend it straight with a 20 ton press. You may be right about bending as a result of tilting too far to the right. The previous owner had a root rake put on this machine and maybe he used the rake in right tilt position to try to remove stumps and bent it? He was in the tree business. He tried to tell me that this year machine only tilted to the right? I don't believe that, we'll see when I get the tilt rod straight and get it re-installed. I'll post pictures when that's done. Bob

 

[BMsuper]

Well, I removed the bent tilt rod, put it on the 20 ton press and straightened it without heating it. I re-installed the tilt rod and was really disappointed that the blade would not tilt further to the left? It appears the angle cylinder is not pulling in all the way on the left side when angled left, and the cylinder on the right should, I think, be extended all the way out when angled left? And, just the opposite when angled right. The right angle cylinder should be all the way retracted and the left angle cylinder should be extended all the way? Am I correct?

The angle cylinders seem to be too far extended and may have caused the tilt rod to bend? If I hold the angle control to the left should the left angle cylinder pull in all the way? For whatever reason the angle cylinders seem to be too far out. I need to hear from someone that has the same blade setup that I have to find out how these angle cylinders work. I gave up today but will get after it on Saturday.

How do the angle cylinders work? Does one pull in while the other extends? If I hold the angle control should the cylinders pull in and extend all the way out? Does the extending cylinder push the other angle cylinder in? Should it go all the way it? Because it does not?

 

[BMsuper]

Doing more research on this 1978 D31A-16. It appears that the angle cylinders are supposed to be a certain length (1760-1780mm) when operating properly. There is a procedure to bleed the angle cylinders. I will try this Saturday to see if that solves my "no tilt to the left problem". I'm learning!

 

[HarleyHappy]

There is also the possibility that there is internal damage on one or both of the cylinders.
Maybe a nut has come off of the rod. If they have been over extended, where are the ports and are there bumpers inside?