Section for komatsu d20,21 and similar grey market dozers

I’d like to point out a very important distinction between the D20 and D21. Although both machines use hydraulic pressure to actuate the steering clutch servo cylinders the D20 gets its pressure from a pump in the oil cooled wet clutch. It operates at a much lower pressure than the D21.
The D21 has an automatic transmission with built in hydraulic pump. The operating pressures for the D21 with the pump in the transmission are much higher than the D20.
The table is on the 2nd and 3rd page of section 22 POWER TRAIN TESTING AND ADJUSTING.
As far as steering clutch slippage there are a number of reasons you may have lost power.
Is there oil or water or rust in the clutch pack?
Are the inner or outer drum splines so worn as to interfere with clutch plate movement?
Are the inner or outer pressure surfaces of the drums worn beyond spec?
Have you measured the thickness of your clutch plates and do they all stack up to what is required. The clutches don’t have much extra material on them.
Have you made the adjustment to the clutch release arms to what the manual recommends?
Are you sure it’s the steering clutches slipping and not the transmission?

Perhaps I’m the only one who bought a D20 that had been used in salt water so that the track frames and tensioners were rusted to all get out. Perhaps I’m the only person who has tried to get track tensioners repaired after the seals blew from rust pitting. Perhaps I’m the only one who found busted springs in my track tensioner. What I can tell yall is that it is a very costly fix. I was able to get the rusty tensioner yoke rod cut off and replaced by a hydraulic repair shop but the spring and cylinder I had to buy new aftermarket. Komatsu prices were astronomical. The big retainer nut at the back of the tensioner cylinder had to be cut off due to rust. The new one from the dealer cost over 100 dollars.
I love the dozer when it’s working but buying parts is the pits. I wish I knew of more aftermarket vendors for the small parts.

matticeandsons said:

Hello, I'm new to your page! I have just purchased a d21a 7 dozer and I am having a issue with machine not wanting to move when I get a load on it or after it worms up for a few minutes. I have purchased the service manual and it's saying the machine should have 844 psi but I'm only getting a reading of just over 300 on my liquid gage! Any help to point me in the right direction would be great. I have dumped all the oil and have cleaned the tranny strainer. I'm at a lose as to what I should be looking at next!

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matticeandsons said:

I have drained all oils and reinstalled sae 30! In tranny and beval gear case. Pulled strainer from tranny( it was clean).i will check inching pedal in morning.

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The problem with the transmission not pulling came about all at once the dozer just stopped pulling have since put all new fluids checked screens ,all new springs in valve body , new clutches on both sides everything is now within spec pump pressure reads correct I believe now thanks attaboy that is probably correct on the discrepancies between the two specs. Now the dozer will pull usually left side (sometimes both) but less than 2 mins later it stops pulling regardless of what speed it's in. I am guessing the valve body has a Crack any insight is apreciated

oldhousehugger said:

Perhaps I’m the only one who bought a D20 that had been used in salt water so that the track frames and tensioners were rusted to all get out. Perhaps I’m the only person who has tried to get track tensioners repaired after the seals blew from rust pitting. Perhaps I’m the only one who found busted springs in my track tensioner. What I can tell yall is that it is a very costly fix. I was able to get the rusty tensioner yoke rod cut off and replaced by a hydraulic repair shop but the spring and cylinder I had to buy new aftermarket. Komatsu prices were astronomical. The big retainer nut at the back of the tensioner cylinder had to be cut off due to rust. The new one from the dealer cost over 100 dollars.
I love the dozer when it’s working but buying parts is the pits. I wish I knew of more aftermarket vendors for the small parts.

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Check the listings Kent Baugh has for the D20/D21's on Machinery Trader. Last I checked he had about two dozen D20/D21's dismantled for parts and those bottom parts are probably common to many years/models. I've ordered several times from him, and while I hate to spend $300 for a new muffler .. it is what it is. They are $40 from China or $90 from Japan, but neither transaction came to fruition.* For large hardware, like the nut, consider just having one made. I was restoring the rear steering cylinder system on my 1950 Austin-Western Super 88H and had both cylinder end pins made for $60, with nuts. My ride here is an '03 Jag and the lower radiator hose was $170 .. ridiculous yes, but it's a premium ride. These little dozers are in that class as well I think, as mine is 30 years old this year with over 28K hours. I figure my grandson will never need to replace my new $300 muffler by the time he's my age .. he just turned 3-1/2. I feel your pain as to parts pricing .. just consider it an investment .. grin and bear it. You'll feel a little better if you check what it would cost you to rent a comparable machine for a week. Cheers!

*The $40 was Chinese vendor Komatsupartsbook .. aka vapor-parts, and the $90 Japanese vendor wanted $168 for shipping.

loggin said:

The problem with the transmission not pulling came about all at once the dozer just stopped pulling have since put all new fluids checked screens ,all new springs in valve body , new clutches on both sides everything is now within spec pump pressure reads correct I believe now thanks attaboy that is probably correct on the discrepancies between the two specs. Now the dozer will pull usually left side (sometimes both) but less than 2 mins later it stops pulling regardless of what speed it's in. I am guessing the valve body has a Crack any insight is apreciated

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I'd definitely resolve that issue before you burn/score/glaze your new clutch packs. Steering is accomplished in two stages. First stage is valving fluid into the steering cylinder to open the clutch pack, and the second stage is engaging the brake band. If you already know this .. no harm done, but better to err on the side of caution. You should have some clearance (free-play) between the mechanical lever that engages the steering cylinder valve .. I forget but 1-3mm or so. Without that clearance, you may have constant pressure trying to open your clutch pack .. like riding the clutch when daddy was teaching you how to drive a stick at 13.

If your valve body has a leak, it's (the oil) gotta go somewhere. But a leak would make clutch pack opening more difficult .. loosing pressure to the cylinder. You should be able to feel the transition from cylinder engagement to brake while pulling back the steering levers, with the engine off. Also check that your inching/clutch pedal has sufficient free-play clearance. The results from steering lever transition should be symmetrical with both levers as well .. mine's off almost an inch .. waiting on some RoundToit's from Amazon.

When clutches slip, they heat up, and fade .. sounds like the 2 minute phenomenon you describe. Good luck with that amigo.

Have Mitsubishi BD2F I need to change the seals in the track tensioner cylinder
What is the best way to remove the cylinder? I have the seals.
Located in Louisiana

Need help in finding out what year my dozer is?
Its a D21P with the powershift transmission.
Pyramiad tracks and 6 way blade.

Need for parts ............anyone?

Hello Spark.... Dont' remove the cylinder but just remove the front idler by removing the tracks and then you can clean everything up an dreplace the seals. Things may be a bit rusty down there but should be a pretty decent job..

Kensmith69 I need your serial number to run for the year built...

darinray said:

Hello Spark.... Dont' remove the cylinder but just remove the front idler by removing the tracks and then you can clean everything up an dreplace the seals. Things may be a bit rusty down there but should be a pretty decent job..

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Thanks for the info. Will try soon.

can anyone provide a price for a new d21a8 and p8
thanks adam

adam35a said:

can anyone provide a price for a new d21a8 and p8
thanks adam

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Here is a used one for $75K, but a long ways to Australia http://www.machinerytrader.com/listingsdetail/detail.aspx?OHID=10942599 Komatsu has a huge presence in Australia for the big stuff, but maybe inquire in your neighborhood anyway. Good luck ..

I have a komatsu D20-P6 ... I have owned it for several years, it has been lightly used during that time.

- I ran the machine yesterday here on my farm... and it started out working fine. But after a bit I noticed that the Left track was not "driving hard"... it does have a little bit of drive to it.... but if any load at all is applied... it does not drive. The right track is driving nice and hard..... it acts as though the clutch is slipping on that side.

- It was dark when I finished up, so didn't have much of a chance to look at it..... not trying to be too lazy here... (well maybe a bit)... I hope to get down and look at it in the daylight this afternoon. I was just hoping for some good pointers from some that had more experience..... hoping for an easier fix than having to tear into the clutch.

Clutch linkage maybe?That would be easy.Ron G

Pull the drain plug from under the steering clutch section, these machines are supposed to have dry clutches and brakes. If you get oil, you'll have to fix the leaking seal and replace the clutch.

I have a D20PL-6. I know those are the numbers and letters, but not neccessarily in that order. One of the hydraulic hoses that goes to the 6way blade, the cylinder on the left side(sitting on the dozer), which pushes the blade out, has a hose that got cut in two. The other thing that is of immediate importance is that the clutch pedal is stuck is stuck to the floor.

You push it maybe an inch and it will engage the NST(seemingly) and then after glowplug warming the engine will start. I have two batteries to make up 24v- one is a 1000ca group 61 and one is a 600ca battery to fit a Honda or small tractor like a Satoh- tight fit, but it cranks it at 30*.

I'm afraid if I try to pry up the clutch pedal, I'll break something, I did that on my John Deere 420c accidentally when I first go it. Is it safe to pry on the pedal with anything more substantial than your hand and arm strength ? I'm fairly strong and I could not not pull it up. Is the hydraulic hose being cut and allowing air into the system related ?

Finally, can anyone tell me what size hose these used ? NPT or JIC, and is it 1/2 or 3/8 ?

Thanks so much

Does anyone know what HP a D21P might be?

Hi Guys and gals I've been a long time lurker here and have got lots of good info here. I've got a D-20 A-6 and I love this machine.
I've had some hard starting issues and shut it down to do all the maintenance and get it back to starting easy again. So far I replaced the glow plug gauge
and checked the plugs 3 out of 4 tested bad. My question is does anybody have a source for the glow plugs. So far I've gotten $100 a piece and I'm hoping someone
knows where to get them cheaper. Please let me know I really need the machine back up.

kensmith69 said:

Does anyone know what HP a D21P might be?

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40hp