Section for komatsu d20,21 and similar grey market dozers

[Curt James]

Komatsu D21 oil pressure warning light at low RPM’s and idle - new behavior:

Hello, I've got a Komatsu D21P-6 dozer works great. It’s a 1992 Put all new engine fluids and filters in it when I got it, and have probably put 20 hours a month on it over last 2 years and about 80 hours on the oils. Unit has about 4000 hours total on it is my guess. When I use it at operating temperature for 1-4 hours the oil pressure warning light will come on at low RPM once it gets warm. When it starts (ambient air in the 70s) the light goes out quickly as expected at fast idle and does not come on even when at slow idle). After warm-up (temp gauge at normal) I start to lightly work the dozer (doing little more than walk it to the work site) and all seems fine. After 10-15 minutes of light work the temp gauge has climbed to mid normal (typical working temp for this machine in my experience), but when I idle down the oil low-pressure light flickers and comes on. If I increase RPM the light goes out. I continue to work the machine for 5 minutes or so more, but make sure the RPMs are high enough to keep the light out. I should mention that dipstick always indicates full of oil (although it is pretty black, as you would expect). In those 5 minutes it seems to me that I have to continually keep adding a little throttle to keep the oil pressure light out. This of course makes me very nervous. Restart after cool-down yields identical results. I'm am going to change the oil even though it is not due yet. My question really is: Does it seem likely that old oil and filter could cause this problem? I'm also wondering if the oil pressure sending unit may be at fault? What are the odds that the oil pump is actually producing insufficient pressure or volume once this old oil gets warm, or is it likely that the switch is becoming faulty as temperature climbs into 'normal' range? I"m sure the engine is not getting too hot in this timeframe. Obviously, I don't want to tear the engine down or do something major unless I absolutely have to. Is this behavior really unusual, and should I even worry about it as long as I operate it with sufficient RPM to keep the light out? The fact that it's not behaved this way in the past is disconcerting. Any other theories or suggestions? (fyi - I kind of plagiarized this because it is the same issue I’m having so I know it’s happened to others.)

THANKS IN ADVANCE FOR ANY HELP!

 

[Welder Dave]

Put a good oil pressure gauge on it so you know exactly what pressure you have. I think oil lights come on at what ever pressure the sending unit is set for. Sending unit could be bad but check with a gauge to verify.

 

[epirbalex]

Komatsu D21 oil pressure warning light at low RPM’s and idle - new behavior:

Hello, I've got a Komatsu D21P-6 dozer works great. It’s a 1992 Put all new engine fluids and filters in it when I got it, and have probably put 20 hours a month on it over last 2 years and about 80 hours on the oils. Unit has about 4000 hours total on it is my guess. When I use it at operating temperature for 1-4 hours the oil pressure warning light will come on at low RPM once it gets warm. When it starts (ambient air in the 70s) the light goes out quickly as expected at fast idle and does not come on even when at slow idle). After warm-up (temp gauge at normal) I start to lightly work the dozer (doing little more than walk it to the work site) and all seems fine. After 10-15 minutes of light work the temp gauge has climbed to mid normal (typical working temp for this machine in my experience), but when I idle down the oil low-pressure light flickers and comes on. If I increase RPM the light goes out. I continue to work the machine for 5 minutes or so more, but make sure the RPMs are high enough to keep the light out. I should mention that dipstick always indicates full of oil (although it is pretty black, as you would expect). In those 5 minutes it seems to me that I have to continually keep adding a little throttle to keep the oil pressure light out. This of course makes me very nervous. Restart after cool-down yields identical results. I'm am going to change the oil even though it is not due yet. My question really is: Does it seem likely that old oil and filter could cause this problem? I'm also wondering if the oil pressure sending unit may be at fault? What are the odds that the oil pump is actually producing insufficient pressure or volume once this old oil gets warm, or is it likely that the switch is becoming faulty as temperature climbs into 'normal' range? I"m sure the engine is not getting too hot in this timeframe. Obviously, I don't want to tear the engine down or do something major unless I absolutely have to. Is this behavior really unusual, and should I even worry about it as long as I operate it with sufficient RPM to keep the light out? The fact that it's not behaved this way in the past is disconcerting. Any other theories or suggestions? (fyi - I kind of plagiarized this because it is the same issue I’m having so I know it’s happened to others.)

THANKS IN ADVANCE FOR ANY HELP!

Best to stop using the dozer till you know the situation . I was warned when I got my Komatsu that the crankshaft can be ruined well before the oil light comes on because of low oil pressure but still high enough not to trigger the light and small horn at working revs . It was suggested to fit manual oil pressure guage permanently , one that has the working pressure about 3/4's of the way around the dial .

 

[Curt James]

OK WelderDave and Epirbalex..... I will watch some youtube and figure out how to ad a manual oil pressure gauge. Thanks for the advice.

 

[Curt James]

Put a good oil pressure gauge on it so you know exactly what pressure you have. I think oil lights come on at what ever pressure the sending unit is set for. Sending unit could be bad but check with a gauge to verify.

OK WelderDave..... I will watch some youtube and figure out how to ad a manual oil pressure gauge. Thanks for the advice.

 

[epirbalex]

OK WelderDave and Epirbalex..... I will watch some youtube and figure out how to ad a manual oil pressure gauge. Thanks for the advice.

Simple brass t fitting screwed into the current sender unit port , I put my sender unit on top and the oil pipe for the guage on the side so I have both . Suggest you use copper rather than plastic line , having a few rings in the pipe twisted like a spring helps absorb shock or vibration to protect the line . Rings about inch and a half be enough . Getting compatible threads on the tee was the hardest bit , easy and cheap job . I do think though going by your first post you will be repairing the motor .

 

[Curt James]

Epirbalex,
Thanks for taking the time to give me some advice. I will take out the current sender and then use it to try to find a T with the correct threads. I think these Komatsu small engines are really Yanmar engines in Komatsu clothes. The Yanmar's are tough as can be (best there is in my opinion) so I hope you are wrong about me toasting the motor. She doesn't smoke a bit now so I hope I am lucky - which is rare when I get lucky!! Thanks a ton.

 

[cxprestige]

Hello everyone--first post here. I've been lurking for a few months; finally decided to share some of my adventures. Lots of good info and advice on this forum--thanks to all who've taken the time to document and photograph all the work they've done!
OK--I bought a D21A-5 in October. Price was right, but it's needed lots of work and needs plenty more to be nice.
Went to look at it first time--undercarriage like new, no wear on sprockets or bushings, plenty of adjustment on the idler. Wow! Let's try to start it. Scrounged a couple of old batteries, charged and ready, but coudn't get the motor to move--stuck fast, even when prying on the U-joint between motor and trans. The owner came down to 2000. I priced Chinese engine rebuild kits and figured WTH might as well give myself another project. We all need more of those!
Pulling it out of the 8" of mud it was sitting in for 4 years was a bit of a challenge. Between a big 12K winch and his small excavator pushing on the tracks from behind, it finally broke free. Then--not one squeak from the tracks as it rolled smoothly onto the trailer! These must be SALT chains--later models have that option, and these were likely replaced along with the UC. Notice the lack of a tin can covering the exhaust stack. Driving rain got all the way into the #3 exhaust port, corroding the valve and filling the cylinder with rain water. Then of course it froze and cracked the liner. Simple precaution would have avoided all that, and the mouse nest too, but then I wouldn't have this machine.
So 8 weeks later, the engine is totally rebuilt--new pistons & liners, bearings, grind valves, etc. Crank was OK; journals measured well, so standard bearings. New water pump. Rebuild aternator. Rebuild U-joint from engine to trans (fun finding the right cross parts & bearing caps). Now it starts and runs smoothly; no leaks-- great hydraulics will hold the blade up for days.

Drive it around and the LH steering clutch is NOT releasing no matter what tricks I use, including filling the whole compartment with diesel for 3 days. Oh well--it was all gonna have to come apart eventually. In my 40+ years of mechanical experience, shortcuts are usually not worth it. Just take it all apart and do it right, and you'll likely find other things that needed fixing anyway.
Now we're into the steering clutches. What a mess. Wish I hadn't put all that diesel in there--even after draining for a day the clutch dust and rust are in a nice slurry, and flammable too, so I don't want to suck it up with the shop vac. RH side is dry, so easier to clean. Lesson learned.
The friction discs are good, measure 6mm llike new. LH throwout bearing is trashed--yoke has 2" of free play in all directions. Brake control shafts in the cover are flapping in the breeze--those needle bearings are shot too. The shafts are well worn and rusty--had to turn them from 25mm to 24, and use smaller bearings and seals. Also grease fittings in the covers, centered between bearings (2 per shaft), with outer seal installed backwards so excess grease goes to the outside.
Sorry no pics of the engine rebuild, but I'm doing pics of the steering clutch work. Everything I've seen in there leads me to think it was designed originally as a wet setup and changed to dry. Not hard to convert, but I'd have to get different friction material and put extra seals on the final drive flanges to keep the oil where it belongs. Thought long and hard about it, and I've decided to keep it dry, but with some mods I made to increase life and (hopefully) reduce corrosion.
Question: has anyone around here ever used or heard of putting VCI capsules (Vapor Corrosion Inhibitor) in the steering clutch compartments? Brands like Zerust--a little plastic box that's supposed to stop corrosion for 2 years in a 2 foot radius, inside a sealed enclosure. If I cut a small access port in the top, covered with a plate, they can be changed every so often.
I'll be trying it out, and will report back in a year or so. I'll keep posting on other progress too, and see how the Chinese engine parts hold up. They looked good and their QC has improved in the last few years, so I'm hopeful.

 

[Don Shilling]

Hello everyone--first post here. I've been lurking for a few months; finally decided to share some of my adventures. Lots of good info and advice on this forum--thanks to all who've taken the time to document and photograph all the work they've done!
OK--I bought a D21A-5 in October. Price was right, but it's needed lots of work and needs plenty more to be nice.
Went to look at it first time--undercarriage like new, no wear on sprockets or bushings, plenty of adjustment on the idler. Wow! Let's try to start it. Scrounged a couple of old batteries, charged and ready, but coudn't get the motor to move--stuck fast, even when prying on the U-joint between motor and trans. The owner came down to 2000. I priced Chinese engine rebuild kits and figured WTH might as well give myself another project. We all need more of those!
Pulling it out of the 8" of mud it was sitting in for 4 years was a bit of a challenge. Between a big 12K winch and his small excavator pushing on the tracks from behind, it finally broke free. Then--not one squeak from the tracks as it rolled smoothly onto the trailer! These must be SALT chains--later models have that option, and these were likely replaced along with the UC. View attachment 205796 Notice the lack of a tin can covering the exhaust stack. Driving rain got all the way into the #3 exhaust port, corroding the valve and filling the cylinder with rain water. Then of course it froze and cracked the liner. Simple precaution would have avoided all that, and the mouse nest too, but then I wouldn't have this machine.
So 8 weeks later, the engine is totally rebuilt--new pistons & liners, bearings, grind valves, etc. Crank was OK; journals measured well, so standard bearings. New water pump. Rebuild aternator. Rebuild U-joint from engine to trans (fun finding the right cross parts & bearing caps). Now it starts and runs smoothly; no leaks-- great hydraulics will hold the blade up for days.

Drive it around and the LH steering clutch is NOT releasing no matter what tricks I use, including filling the whole compartment with diesel for 3 days. Oh well--it was all gonna have to come apart eventually. In my 40+ years of mechanical experience, shortcuts are usually not worth it. Just take it all apart and do it right, and you'll likely find other things that needed fixing anyway.
Now we're into the steering clutches. What a mess. Wish I hadn't put all that diesel in there--even after draining for a day the clutch dust and rust are in a nice slurry, and flammable too, so I don't want to suck it up with the shop vac. RH side is dry, so easier to clean. Lesson learned.
The friction discs are good, measure 6mm llike new. LH throwout bearing is trashed--yoke has 2" of free play in all directions. Brake control shafts in the cover are flapping in the breeze--those needle bearings are shot too. The shafts are well worn and rusty--had to turn them from 25mm to 24, and use smaller bearings and seals. Also grease fittings in the covers, centered between bearings (2 per shaft), with outer seal installed backwards so excess grease goes to the outside.
Sorry no pics of the engine rebuild, but I'm doing pics of the steering clutch work. Everything I've seen in there leads me to think it was designed originally as a wet setup and changed to dry. Not hard to convert, but I'd have to get different friction material and put extra seals on the final drive flanges to keep the oil where it belongs. Thought long and hard about it, and I've decided to keep it dry, but with some mods I made to increase life and (hopefully) reduce corrosion.
Question: has anyone around here ever used or heard of putting VCI capsules (Vapor Corrosion Inhibitor) in the steering clutch compartments? Brands like Zerust--a little plastic box that's supposed to stop corrosion for 2 years in a 2 foot radius, inside a sealed enclosure. If I cut a small access port in the top, covered with a plate, they can be changed every so often.
I'll be trying it out, and will report back in a year or so. I'll keep posting on other progress too, and see how the Chinese engine parts hold up. They looked good and their QC has improved in the last few years, so I'm hopeful.

I'm in the process of trying to remove the inboard flanges to change the throw out bearings on the steering clutches on my D21a-7. What method are you using to remove your inboard flanges?

 

[cxprestige]

I'm in the process of trying to remove the inboard flanges to change the throw out bearings on the steering clutches on my D21a-7. What method are you using to remove your inboard flanges?

There are 2 tapped holes in the flange for "forcing screws" which just means 10mm X 1.5 by about 50mm long, very high grade bolts. One hole was already used for the tab lock-washer that holds that 55mm nut in place. The other was left open-- I ran a tap through both to clean the threads first. Oil the bolt threads too, just like a gear puller.
I made chocks for them to bear against to spread the load. Tightened a little at a time on each side until they were really pushing hard, then got behind the flange with a long wedge and one hard whack popped it free.
This process may hurt the throwout bearing, but it's gonna be replaced anyway.
Word of caution--whenever you're working on a taper fitting like this, screw the big retaining nut back on a couple turns so when the flange breaks free it stays on the shaft instead of exploding into the compartment and crushing whatever's in its path. There's a lot of force there! They're supposed to be pressed back on with 6 tons. Probably have to use a Porto-Power with short cylinder.

The outer flanges are set up the same way, but with 12mm holes. I took those off too, to replace the final drive seals.
Pics show these parts after cleaning and painting--needless to say, it wasn't that nice in there to start with.

More to follow on throwout bearing replacement, with pictures.
In the meantime, a happy Thanksgiving to all!

 

[Don Shilling]

I'm in the process of trying to remove the inboard flanges to change the throw out bearings on the steering clutches on my D21a-7. What method are you using to remove your inboard flanges?

There are 2 tapped holes in the flange for "forcing screws" which just means 10mm X 1.5 by about 50mm long, very high grade bolts. One hole was already used for the tab lock-washer that holds that 55mm nut in place. The other was left open-- I ran a tap through both to clean the threads first. Oil the bolt threads too, just like a gear puller.
I made chocks for them to bear against to spread the load. Tightened a little at a time on each side until they were really pushing hard, then got behind the flange with a long wedge and one hard whack popped it free.
This process may hurt the throwout bearing, but it's gonna be replaced anyway.
Word of caution--whenever you're working on a taper fitting like this, screw the big retaining nut back on a couple turns so when the flange breaks free it stays on the shaft instead of exploding into the compartment and crushing whatever's in its path. There's a lot of force there! They're supposed to be pressed back on with 6 tons. Probably have to use a Porto-Power with short cylinder.
View attachment 205855 View attachment 205856View attachment 205857
The outer flanges are set up the same way, but with 12mm holes. I took those off too, to replace the final drive seals.
Pics show these parts after cleaning and painting--needless to say, it wasn't that nice in there to start with.

More to follow on throwout bearing replacement, with pictures.
In the meantime, a happy Thanksgiving to all!

So far, you have provided more info than all the videos on youtube! How much is involved in replacing the two oil seals?

 

[cxprestige]

How much is involved in replacing the two oil seals?

Well, in the 5 series, the final drive seal and inner bearing come out through the steering case. I just pried it out and pressed the new one in, also dressed the sealing surface on the flange. If that face is really worn it might need a speedi-sleeve and smaller seal.
From looking at the parts books, it appears the 6 series and up have a different setup, and all that stuff is accessed through the final drive case itself, which means pulling tracks and sprockets. If the seal isn't leaking it's probably not worth the trouble to replace unless you've already got the tracks off. That seal is above the level of oil in the final anyway, so it's not under static pressure--only wet when the track is moving.
The inner seal on the bevel gear shaft (behind the throwout assembly), comes out through the steering housing on both series, and could likely be done pretty easily. I'm not doing mine 'cause they don't leak, and this project is taking long enough as it is !

 

[Don Shilling]

Doing some more cleaning and painting of Komatsu D21 steering clutches today. Also, studying the blade control valve. I have a leak on the blade up/down spool. The clevis needs to be removed in order to replace the seals. I've been told to heat the top of the shaft in order to soften the lock tight then hold the shaft with a vice grip and unscrew the clevis. Anyone done this before?

 

[cxprestige]

Here's some more on steering clutch throwout bearing work. The wear was pretty severe on all moving parts in that throwout linkage. Original bearings were shielded, not sealed type. One was completely trashed, the other rusted almost solid. I replaced them with double sealed bearings, which seem more appropriate to a dry setup. Drilled and bushed the bearing carrier, where the pivot screws engage it. Had to build up the ball joints on the ends of the yokes and grind them back--manual says 22mm is the new dimension, but the sockets were so worn out I made one 23mm and the other 24.

 

[cxprestige]

The manual says to grease that yoke ball joint when assembling. That grease will hold clutch and brake (and rust) dust, and turn into a nice grinding paste after a few hundred hours, as it already did! I thought, Why not use the same approach as car ball joints and put a boot over it? They can last 100,000 miles in rain, road salt, etc. So I rummaged around on the high shelves and found a box of old VW driveshaft boots. Cut one down to fit over the socket in the bottom of the steering case, and the small end snaps nicely over the ball joint. Now the grease and the dirt will hopefully stay in separate places.

 

[Don Shilling]

The manual says to grease that yoke ball joint when assembling. That grease will hold clutch and brake (and rust) dust, and turn into a nice grinding paste after a few hundred hours, as it already did! I thought, Why not use the same approach as car ball joints and put a boot over it? They can last 100,000 miles in rain, road salt, etc. So I rummaged around on the high shelves and found a box of old VW driveshaft boots. Cut one down to fit over the socket in the bottom of the steering case, and the small end snaps nicely over the ball joint. Now the grease and the dirt will hopefully stay in separate places.

Outstanding fix! I was wondering what could be done to protect that socket. I'll get a pair of VW boots for mine today!

 

[cxprestige]

So I rummaged around on the high shelves and found a box of old VW driveshaft boots. Cut one down to fit over the socket in the bottom of the steering case, and the small end snaps nicely over the ball joint. Now the grease and the dirt will hopefully stay in separate places.

The boots I used were for older Rabbit / Jetta from 1970s--I don't know what the part # is, but you could probably take measurements of the socket boss and the ball, and find a generic part at NAPA that would do the job. I had to cut off all but the first 2 pleats, and also cut a flat on the side where it's up against the housing. It's not a perfect seal, but certainly way better than nothing!
Oddly enough, that ball and socket are listed as separate units in the parts book--they would have to be ground off and the new ones welded in, if they were even available.

 

[Don Shilling]

So I rummaged around on the high shelves and found a box of old VW driveshaft boots. Cut one down to fit over the socket in the bottom of the steering case, and the small end snaps nicely over the ball joint. Now the grease and the dirt will hopefully stay in separate places.

The boots I used were for older Rabbit / Jetta from 1970s--I don't know what the part # is, but you could probably take measurements of the socket boss and the ball, and find a generic part at NAPA that would do the job. I had to cut off all but the first 2 pleats, and also cut a flat on the side where it's up against the housing. It's not a perfect seal, but certainly way better than nothing!
Oddly enough, that ball and socket are listed as separate units in the parts book--they would have to be ground off and the new ones welded in, if they were even available.

I'm still looking for the proper boots. The guys at various parts stores can't come up with the suitable size for this application. If you happen to come across a part number or other info, it would be greatly appreciated. These boots are an excellent idea and I would surely like to incorporate them on reassembly.

 

[Don Shilling]

Another item that came to light today, on my D21, The 8 taped holes on the back of the dozer that are drilled into the steering clutch case. I thought they were 16 mm and even run a 16x2 tap thru all of them. When I inserted a 16x2 bolt and snugged it up, the bold pulled back and jumped the threads like it was one size too small. Did I miss-measure the holes? I'm old school and not all that keen on M and M's!

 

[MasterofDiaster221]

Not sure if I am in the correct place but I just got a d65-12 machine has been sitting for several years. I got the machine started up and moving a little after changing all filters and fluids and had to replace all cables for throttle and shifter and drive control cables. Problem I am having with the machine is when in forward only the left side track pulls same goes for reverse it only pulls on left side. The right side will pull track tension in forward and reverse but has no power to turn