komatsu 450 wheel loader, hydraulic problem.

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This topic contains 15 replies, has 13 voices, and was last updated by  Aissaoui 1 year, 5 months ago.

Viewing 15 posts - 1 through 15 (of 17 total)
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  • #25509 Reply


    hello everyone. I have a problem with the hydraulic system, the oil overheats. I replaced the filter and water pump, cleaned coolers and still is overheating. What may yet be the cause. Please advice. Thank you.

    #27408 Reply

    Hi Mike,
    There is so many possibility,but let’s start with basic.
    -is your hydraulic fluid in good condition or is it the correct grade?(sae 30 for summer).
    -does it occur all the time or only when specific operation?
    -is there hydraulic cylinders drifting anormaly that would indicate internal by-pass?
    -do you get all the power out of your hydraulic pump?worn pump generates heat due to excessive internal leak.

    Good luck!

    #27409 Reply

    Ron Mellor

    Mike, It’s been my experience that the major cause of heat will be a bypassing relief valve or pressure reducing valve.You should be able to find the cause of the heat by listening to the hydraulics. You will hear a loud hiss if either are these are faulty. If it’s a relief just touching the fittings in the suspect area will give you a good indication of the circuit at fault. If it’s a pressure reducing valve just check at the tank side of the valve bank. Both will be to hot to touch. if it’s a pump, give it the 4 second touch test. If you can keep your hand on the pump for 4 seconds it is most likely good. If not, go to the next step, check case drain flow. The numbers for case drains are often hard to find, use the general rule 1GPM per 1000PSI. or if you fill a twenty Lt. pail in less that a minute. the pump is toast. Let us know what you find.

    #27410 Reply

    Jim Owen

    These suggestions the members have put forward are very, very good. There is very good advice here.

    I had one instance of a piece of equipment overheating and going to high heat Engine shut down. The hydraulic oil temperature was roughly the same temperature as the engine, and I assumed the hydraulics were at fault. I searched through that hydraulic system; I searched for days. I checked every valve, every reducer, the heat exchangers, everything I could think of. I could find no place where the hydraulic system was abnormally hot. The heat gun that I used to search every component could not place any kind of abnormal heat load.

    What I eventually found was the engine was overheating the hydraulic system via the heat exchanger.

    As it turned out the fuel injection pump, a distributor style, was failing to advance the engine timing. Because the engine was running late while loaded, the exhaust gases were heating up the exhaust manifold and the engine head, heating up the water to 200+ degrees which, in turn, heated the hydraulic fluid.

    My point is this: keep your mind open to other possibilities.

    #27411 Reply

    I assume that when you said you cleaned the cooler you mean the outside fins,you may want to do a check on the flow of the cooler also because I have seen a good many coolers plug up inside and restrict flow which instead of cooling the restriction causes more heat.You should check the service manual for a thermal bypass valve also,this keeps the hydraulic flow out of the cooler untill the oil reaches a certain temperature,it may be staying closed and the oil is not getting to the cooler.A heat gun is most valuable as the other guy’s have said,I once had a John Deere loader with a piece of rubber stuck into the steering valve and that drove it’s oil temperature through the roof.Good luck with finding the problem.

    #27413 Reply


    if oil is overheating and coolers woorking good not sure off cooler type you have air or water cooler ,you may have a restiction in the hyd system some wheres listen for oil going over relefe valave continusly or bypssing some wheres , if the cooolers you have are of the air type in front of rad maybe, remove cooler and have checked for flow or be sure they are clean between the rad and cooler, places you cant see and providing this loader has not had the wrong hyd oil put in good luck ,you can use a digital infered temp gun to find where the point of heat is being generated

    #27431 Reply

    Jim Owen

    Regarding the use of a heat gun for troubleshooting: a very necessary tool!

    And to take it a step further, test your machine with the heat gun when everything is up to temperature and working well. Check the inlet and outlet of coolers, pumps, and motors and control valves, all the places that can be heat generating. Mark them with a dot of paint where the temp was taken.
    Record those temperatures and keep them on file. When things start to go wrong, you will know what the temps were and be able to compare to what they are now.

    Base reference points are handy.

    #27462 Reply

    Depending on if its a newer model weather it is a -5 or -6, the dash 6 machines have had factory campagines for hydraulics overheating due an improper casting creating a smaller them required orifice in the pump causing the hydraulics to over heat, so check with your local dealer if it is a newer machine -5 or -6. and see if your machine falls into the capagine

    PS- I work for SMS Equipment in fredericton,NB, Canada and have preformed these pump replacements

    #27804 Reply

    we had a 450 komatsu over heating here in fla. while working for linder mach. you didn`t state -5 or 6 but check the hdy. fan for problems you can go in monitor and demand 100%fan speed and check with a hand held tach . also had one where parts were thrown at the unit took cooler out and had flushed but we were not told of a previous pump failure .we finally took cooler out and cut it open in a band saw the bottom half of the cooler was completely plugged…you see flushing is good but like a a/c condensor the flush will only flow through the less restricted ports..

    #27805 Reply

    John Whelan

    Excellent tips suggested here! I agree with the infrared heat gun approach. You can measure the heat differential throughout the hydraulic and cooling systems possibly pin-pointing the problem area. The engine temperature is relative to oil temperature like Jimo mentioned.

    #27831 Reply

    Than Zaw

    check Head Gasket, Thermostat, Engine Oil pump and Oil Gallereies.

    #27973 Reply

    Scot H

    It drives me nuts when someone takes the time to register and ask a question. A bunch of people try to give advice and the original poster doesn’t come back and say if it has been fixed or what the problem was.

    Maybe I am weird but I enjoy reading threads where someone has a problem and either by themselves or with the help of others they get their problem solved. Most times I actually get to learn something from reading them.

    #28415 Reply

    Bri Guy

    Not sure if you have fixed the problem yet but if it is a -6 loader with piston pump for steering the problem is the steering pump will not return to minimum angle inneutral position causing a horrible overheat there is a campaign for this as described komatsu wheel loaders motly rely on hydraulic tank for cooling the dash -6 loaders have a small hyd cooler on the fan motor return this is just to take care of the heat generated from the motor(fan motor that is)

    #39077 Reply

    Jeff miller

    I am working on a komatsu wa380-6. Work pump failed.
    And I believe that a similar comment is mentioned in a reply that I read. There is an update to the steer pump and work pump due to fluid flow in piston pumps. The Piston hole portion worn from debris in circuit which entered into servo piston. Abnormally worn piston hole leaks servo piston control oil, and pressure is hardly able to rise. Swash plate gets fixed on maximum side, and large pump flow rate continues which causes overheating.

    #44867 Reply


    hello sir i have a probleem with mi komatsu 450 1 it wil not lift on idle

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