Komatsu PC300LC-5 Travel Motor problem

[Cliff Smallwood]

New Member. I have a Komatsu PC 300LC-5, Ser# A20416, Travel motor type #HMV280ADT. The travel motor blows the shaft seal and pressurizes the final drive.

I ran time test, H.O. and H high idling, at low speed 56.4 sec (book standard value 53.8 +/- 3 sec) and at high speed 58 sec (book standard value 33.3 +/-2 sec) .

I ran travel motor case drain leakage test, H.O and H high idling pin locked sprocket for 1 minute, and got 1 cup of oil from the case drain. (book standard value of 20 liters per minute and a max permissible value of 40 liters per minute)

Could the safety valves or the balance valve inside the travel motor prevent the case drain flow from meeting spec? If this is happening would this cause the travel motor to blow the shaft seal?

Thanks
Cliff

 

[Cliff Smallwood]

I have a typo in the above post, ...At high speed 33.7 (book standard value 33.3 +/-2 sec)

Sorry

 

[uffex]

Good day
Often the case drain filter has blockage or the viscosity of the fluid is to high. If you check the pressure at full stall it should not exceed 0.5 bar.
Kind regards
Uffex

 

[Cliff Smallwood]

During the full stall case drain leakage test, the travel motor drain port is open to atmoshpere (no back pressure).

The travel motor case drain flow during the full stall case drain leakage test (1 minute duration) was 1 cup, the Komatsu new travel motor standard drain flow is 20 liters per minute, a huge difference.

Something in the travel motor is preventing the case drain flow from leaving the motor.

 

[John C.]

Does the machine walk straight when you are traveling up a hill? Do both tracks turn with the same amount of power in either direction?
It's possible that the swivel is leaking on the land next to the feed for one of the travel motors and being slugged with too much flow causing a back pressure situation. You might also dig out all the dirt where the hoses go through the carbody. I've seen rocks and dirt in there pinch off a case drain hose. You might also check your return filter and the suction strainer in the tank for shiny things. If the motor has a problem, there will be brass in the tank.

 

[Cliff Smallwood]

John C.
I repacked the swivel joint first, none of the seals where broken or coming apart, just thinner than the new seals from normal wear.

I replaced the face seals on both travel motors last year, and at that time, I sent the travel motor with the blown shaft seal to be repaired. Hydraulic shop disacembled the travel motor and found no damage or replaceable parts other than shaft seal and new o-rings.

After re-installation, the travel motor lasted about a month before the shaft seal started pressurizing the final drive case again.

How can the travel motor case drain flow (1 cup per minute vs. 20 liters per minute/new motor spec) during the full stall case drain leakage test be so for off of Komatsu's new motor design specification? Or is my Shop Manual printed wrong? My shop manual calls for 20 liters per minute (design standard) and up to 40 liters per minute (maximum permissable) of case drain leakage from the travel motor.

 

[Tones]

Well this is a head scratcher, low volume of oil and high pressure. Which way is the shaft seal blowing? Towards the motor or gearbox. I have seen both, not Komatsu though.

 

[John C.]

I'll have to ask you a couple of questions first off. Where did you get that spec for case drain. I have an original PC300 PC400 service manual from the factory and it doesn't have that spec. Can you take a photo of the page that shows it?

In my experience anything more than one liter is a concern and the motor and final would have been removed and torn down for inspection. Was the shop that tore down the motor and resealed it a dealer or a job shop? You say there was nothing to rebuild, but I have done many of those motors and finals and there are many considerations. Was the seal plate lapped to the end of the barrel assembly? What did the piston feet look like? Was the swash plate lapped back to flat? Were the pistons and bores in the block measured and the clearances checked. Was the motor tested on a dyno or just sent back to you without being operationally tested?

At any rate if all the things that you say you have done are good, and I believe what you are saying, then the only obvious answer is that there is something wrong in the motor. If that is the case, then the case drain spec that you are providing is likely wrong. I'm only putting this out for your consideration. The direction that you take to fix the problem is up to you.

 

[Cliff Smallwood]

Tones:

The travel motor shaft seal is blowing out toward the final drive.

 

[Cliff Smallwood]

John C.
Shop Manual CEBM207077, Section 20 Testing and Adjusting, page 20-7, Leakage of travel motor, Standard Value Max. 20 liters per minute, Permissible Value Max. 40 liter per minute.

I will have to send a picture of the page later.

It is a job shop and I watched the motor run on the test stand. The test stand was not set up to the stall the motor. After tear down, the shop Owner called to ask if the motor was new, because as he said, they could not really see any wear other than the blown shaft seal and the o-rings under the small allen head bolts on the final drive side of the case.

The Komatsu Tech at my dealer in Dallas said that the stall case drain test proved that the swash plate, seal plate, barrel assembly, and pistons were good in the travel, but since the motor was blowing the shaft seal I should just order a remain. motor.

I don't think it is a good idea to buy and $8,000 dollar motor and then have the same thing happen to the new motor.

Other than draining the final drive case every so often, the travel motor functions fine in both directions and at both speeds.

 

[heymccall]

On my Cat excavators, the travel case drains tee into the swing drive case drain before returning to the tank.
I'd start by measuring case drain for all 3 units (both finals and the swing).

As for your case drain spec, what volume comes out of the other travel motor?

 

[John C.]

The other question is did you stall the tracks when you checked the case drain. By the way 20 liters is 5.2 gallons. That is totally wrong.

Post the page and I'll do some checking with my contacts.

 

[Cliff Smallwood]

Dear John:

I followed the instructions in my Shop Manual (see attached). H.O. and H. mode, engine at high idling, lock pin installed between sprocket teeth and frame, relieve travel circuit.

 

[Cliff Smallwood]

Dear Heymccall:

I have not tested the other motor yet, the weather has been bad, maybe Thursday. The shaft seal on the other travel motor is not leaking into the final drive.

 

[heymccall]

No, but excess case drain pressure can come from outside the failed motor, such as the other final drive, or the swing motor (or the rotary joint, or a pinched hose).

They all share the same 1/2 hose to the tank. That motor may over pressurize it's case from another motor's case drain (swing or final) and it may just simply be the weakest link.

 

[Cliff Smallwood]

Dear John C.
After reviewing Shop Manual description of the Brake and Safety Valve function of the travel motor, I have the following question.

Can a non-functional safety valve, check valve, and counterbalance valve in the travel motor allow the pressure inside the travel motor case to spike and blowout the travel motor shaft seal? If this is possible, how would you test the travel motor safety valve settings?

 

[John C.]

The travel motor reliefs are checked with the sprocket blocked with a pin and you can install the gauge at the pump to read it.
No they will not cause the seal to blow out unless the motor has a problem as we described before. They relief into the return to tank hose which ever that may be by the direction you choose. The counterbalance valve keeps the motor from turning into a pump and putting a negative pressure on the supply side of the motor. The flow and pressure will stay inside the motor if it is not internally damaged.

 

[Vetech63]

The case drain fluid volume is based on leakage in the high pressure loop of your hydrostatic drive, whether its a motor or pump. Excessive case drain leakage means that there is a leak in the high loop. There is no way a 40 liter case drain spec is right. I'de bet you have a case drain restriction somewhere like Heymccall said. You aren't throwing some cheap ass seal in this thing are you?

 

[Cliff Smallwood]

Dear Vetech63

All o-rings and seals were provided by Komatsu.

 

[Hydraumind]

Also stall the travel motor on reverse and check again for case drain leakage.
You have the A and B main hoses, the case drain hose and the travel speed hose, be sure you disconnect the case drain hose and close it from the machine side while testing