Track/travel motor issue.

[theblacksmith]

Hi guys. My PC30-7 track(l/hand )has started to malfunction in the 1st speed. In the fast speed(button pressed) its all good - no gear noises - no change from what it should do. So gears must be all good hopefully. Im picking up machine later on today to bring to yard for washing and checking this problem out. To me it sounds like an o-ring/hydraulic leaking problem somewhere. When I lift track off ground and track in slow speed its really struggling for some reason- both ways. Sounds like oil is not completing the circuit and pressurizing against itself somewhere. Sometimes it comes right if I play with the 2 speed button. I was just wondering if any of you have come across this problem before? When I have the machine back here i will remove case drain from the drive motor and see what happens then.Also I will need to rule out the center rotary coupling. I went to see the mechanics at Komatsu here yesterday and a couple of them mentioned it could be the swash plate in the motor assy not moving properly maybe?The other side motor functions as it should.Any help or info or ideas would be greatly appreciated.The machine is well maintained always.All oil and filter changes done as per Komatsu recommendations.The machine has done 4600hrs.Thanks in advance.

 

[DanRooks]

How much does Komatsu want for a new motor? Do they offer a rebuilt one? If so how much $? Did they offer to rebuild your motor? If so how much $?

 

[Zed]

Check the brake pressure at low and high speed. Not sure about the small Komatsu's but Hitachi use the same supply to release brakes and change motor swash plate angle for low and high speed. So low speed has enough pressure to release the brake, then when high speed is switched, the pressure increases to change motor angle to high speed. It's a lot more complicated than that with numerous valves, but thats about it in a nutshell.

it may not be the same system but its always good to check and confirm pressures.

 

[John C.]

You need to pull the suction strainer in the tank before you start pulling motors and doing a lot of tests. If you find a bunch of brass in the basket I would probably then do the case drain test. A lot of brass and lots of oil out the case drain pretty well set you up to pull the motor. All I recall the motor and final drive on those are all one piece.

Do you have rubber tracks?

 

[theblacksmith]

Check the brake pressure at low and high speed. Not sure about the small Komatsu's but Hitachi use the same supply to release brakes and change motor swash plate angle for low and high speed. So low speed has enough pressure to release the brake, then when high speed is switched, the pressure increases to change motor angle to high speed. It's a lot more complicated than that with numerous valves, but thats about it in a nutshell.

it may not be the same system but its always good to check and confirm pressures.

Your theory makes sense mate - I will investigate that - it only a 3 tonner so very handy to work on. I never thought of the brakes-cheers.

 

[theblacksmith]

How much does Komatsu want for a new motor? Do they offer a rebuilt one? If so how much $? Did they offer to rebuild your motor? If so how much $?

I didnt ask mate - I have a fair idea.(lots)
Thats why I want to fix the thing myself.
If we all ran to the manufacturers-forums like these would die in my opinion. They wanted to charge me for some diagrams even(3xA4 sheets lol)!! Im a time served engineer and coded welder so it s not nuclear science really,and for the next couple of weeks - time is on my side.Cheers.

 

[DanRooks]

Maybe in 20 years the OEM.s will have their service info on the internet

 

[John C.]

The brakes work off the supply oil to the motor. There is no brake oil pressure to test. The two speed travel works off a solenoid that sends oil to a piston that changes the swash plate angle. Pressure makes the travel motor swash plate go to minimum stroke for high speed.

Most all the manufacturers of heavy equipment have had their info on line for some time now. They just want to charge you for the use of it. Some will provide parts pages for free but I don't know of any that provide service information unless you subscribe to a service.

Good Luck!

 

[theblacksmith]

Cheers Guys-Im off to a motorcycle rally over the weekend - I will get my hands dirty with it next week. I ll keep you s posted.

 

[PD Mech Steve]

Could also be a swivel joint issue. After a while they leak internally and oil is bypassed to other ports causing symptoms you describe as well as others. Good luck. Steve. www.pdmechanical.com

 

[kb1]

Reviving an old post, for others who may come looking.

The service manual says that the travel speed of the PHX300N-33 track motor is varied by varying the configuration of the ports in valve plate that oil is delivered to and removed from rather than varying the stroke of the pistons. The speed selection occurs within the motor body.

Low Speed ... all the pressure oil from the travel control valve is supplied to valve plate port A, A1 and A2 in parallel (or B, B1, and B2, depending on direction of rotation), so the piston becomes a large capacity motor that acts from the top dead point to the bottom dead point.

High Speed ... the supply of pressure oil from the travel control valve to valve plate port A1 and A2 (or B1 and B2) is shut off, and pressure oil is supplied only to port A (or port B). As a result, the piston becomes a small capacity motor that acts only on a fixed part in the stroke.

The valve plate ports can be visualized as disk with, beginning at noon and travelling clockwise, ports B1, B, B2 and then ports A2, A and A1.

When high-speed is selected ports A1, A2, B1 and B2 are connected to each other with balanced pressure, so perhaps the stationary valve plate has been damaged between either ports A1 and B1 or B2 and A2 and when pressure is applied to those ports in low-speed the flow is leaking across the plate and oil is bypassing the pistons.

Alternately, as you mention that fiddling with the 2 speed button sometimes fixes it for a while, perhaps the spool internal to the motor that controls valve configuration is sticking/contaminated/damaged.

I'd be interested to know what the final diagnosis was.

 

[Hydash NZ]

Hi,
Jeremy from Travel Motors Direct in Tauranga, NZ. If you've eliminated everything else and believe it to be your final drive at fault then give me a call and we can discuss further final drive troubleshooting . We specialize in excavator final drives and have had a lot to do over the past 20 years with komatsu, specifically Hydash and Nachi.Our contact details are located on our website, look forward to talking to you. Jeremy