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Thread: Komatsu D38E master brake problem

  1. #1
    Super Moderator willie59's Avatar
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    Komatsu D38E master brake problem

    Had a customer bring in a D38E to change oil and filters, replace belt tensioner, and look the machine over kinda stuff. Got everything done, including cleaning his OMG clogged radiator.

    Was driving it on the lot today checking it out and noticed the master brake pedal didn't do anything. Hmm. Now I don't know a whole lot about the D38E, but I know the master brake pedal directly operates a control valve, and I know the valve spool is operating. Hmm. So I tried driving the machine and throwing down the safety lever, still didn't engage master brake/parking brake. Hmm. I'm going to let customer know this on Monday and see if he wants me to look into problem, 'tis a bit dangerous like this. Anybody know the nuts and bolts of the master brake/parking brake operation on this machine? Steering brakes work fine for steering, just a problem with master brake.
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    Member FWD's Avatar
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    In the upper area where the final drive bolts to the frame there is a lock nut (large) I don't remember the size, (over 1") It's on the front upper part of the final drive bolt circle. You loosen the lock nut and tighten the inside bolt, (3/4) I think. There should be several threads remaining or you need to change the brake lining. You don't want to run the brake all the way to the end otherwise it's metal to metal and the metal goes in all the rear end parts.
    Hope this helps. I know Dressers some, D38E should be the same as a TD8-H.
    FWD

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    Super Moderator willie59's Avatar
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    Cool, thanks FWD.
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    If the machine is steering correctly I doubt the brake is out of adjustment. If memory serves me correct they are hydraulically applied brakes not spring.

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    As I recall when those were TD8H machines the single pedal was more a decel pedal and less a brake. I used to make decel pedal as an aftermarket add on for those machine when they were equipped with a winch. The problem was you had to let up on the brake to get the engine rpm up but then the machine was pulled backwards by the winch.

    Again, as I recall the pedal would only stop the machine when it was almost fully depressed because the decel function had to work first. It would not surprise me that the linkage adjustments have worn some and now the brake won't engage. As I recall the linkages had to be adjusted to make it all work proper.

    Good Luck!

  6. #6
    Super Moderator willie59's Avatar
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    Well, the customer didn't want me to check it out, needed the machine.

    I'm certainly not a dozer expert, but the comments here are interesting. Are we saying the Komatsu D38E is an evolution of the TD8? One thing that caught my eye, Aside from the fasteners in the Cummins engine, all the bolt/nuts that assemble the machine are SAE fasteners. Haven't see that on a Komatsu before. And the machine was built in Poland.

    The customer did mention that when he depressed the decal pedal all the way, it would apply the brake. I was curious why the decel had a pedal lock button on the floor plate, that explained that. My question, what is the pedal on the left for, I assumed that would be a master brake pedal, that's the one that didn't seem to do anything. And I also noted the brake didn't apply when you dropped the safety lever. Is that normal?
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    Member FWD's Avatar
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    No brake on when you drop the safety lever. That's normal. The pedal lock is the parking brake. I don't know what the pedal on the left is for. I have run TD8-H's and own a TD9-H. I had a TD8-E it had a separate pedal for braking. It did have a decelerator.
    The Komatsu D32, D38, D39 were made in Poland by Dresser. The tin work was different along with the paint. They used some of the old IH tooling, thus the SAE bolts etc. Dozer made in Poland SAE, engine made in U.S. metric.
    FWD

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    Super Moderator willie59's Avatar
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    Quote Originally Posted by FWD View Post
    Dozer made in Poland SAE, engine made in U.S. metric.
    FWD
    Yup, things that make ya go hmm.
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  9. #9
    Senior Member John Canfield's Avatar
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    I'm not handy to my D39, but I think the left pedal is brake, and the right pedal is deacellerate and brake. Even though my D39 has less than 1300 hours, I need to stand on the pedals for any braking.
    John
    1999 Komatsu D39P-1

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    D39P-1 2001 model. Secondary Brake hydrulic problem. The decelerator/main brake works fine, except that brake is mechanical, so of course is harder to press. The left side brake pedal is hydrulic.
    When I step on it, it does activate a hydrulic control valve. But brake does not work. The brake pedal feels like it is hitting a hard stop, though I cannot see on. Only thing I can guess is that Hydrulic Valve is 'bottoming out'. Does anyone know if the hydrulic brake pedal and the decelerator brake pedal work the same set of brake pads? Does anyone know if there is any adjustment for the hydrulic brake pedal (anywhere between the pedal and the actual brake pad). I cannot seem to find one and the repair manal is not very helpful in diagnosing problems with the Hydrulic brake. Any help is very appreciated. Stacy Whetzell

  11. #11
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    The left brake (hydraulic released and spring applied) works the same pads as steering brakes. You can look in the left door above the battery and see the brake release port to over ride the springs with a dead engine or hydraulics. There are adjustments for spring engagement under the rear cover. Its a balancing of right mechanical and left spring applied(hydraulic release) linkage and steering brakes to pads.

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    Thanks so much IronDirt. Good answer

    I wish there were an easier way to do this than having to remove rear cover - but guess there are no short cuts.

    thanks much
    Stacy

    Quote Originally Posted by Iron@Dirt View Post
    The left brake (hydraulic released and spring applied) works the same pads as steering brakes. You can look in the left door above the battery and see the brake release port to over ride the springs with a dead engine or hydraulics. There are adjustments for spring engagement under the rear cover. Its a balancing of right mechanical and left spring applied(hydraulic release) linkage and steering brakes to pads.

  13. #13
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    Before you pull the cover you could hook up a pressure gage to the emergency port to make sure the pressure falls to zero, this should apply the brakes if working properly.

  14. #14
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    Quote Originally Posted by willie59 View Post
    Had a customer bring in a D38E to change oil and filters, replace belt tensioner, and look the machine over kinda stuff. Got everything done, including cleaning his OMG clogged radiator.

    Was driving it on the lot today checking it out and noticed the master brake pedal didn't do anything. Hmm. Now I don't know a whole lot about the D38E, but I know the master brake pedal directly operates a control valve, and I know the valve spool is operating. Hmm. So I tried driving the machine and throwing down the safety lever, still didn't engage master brake/parking brake. Hmm. I'm going to let customer know this on Monday and see if he wants me to look into problem, 'tis a bit dangerous like this. Anybody know the nuts and bolts of the master brake/parking brake operation on this machine? Steering brakes work fine for steering, just a problem with master brake.
    Dropping the safety lever should put the joy stick in nuetral but not engage the brakes.

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