Hello everyone, I have a Komatsu PC90 that overheats after about an hour of use. I have changed all cooling related parts such as new radiator, thermostat, cleaned between radiator and oil cooler, inspected fan and foam seals around fan. Nothing has not improved it. I can run without issues if the outside air temperature is cold, but if it gets hotter than about 50deg F out, I have to take many breaks and run with hood open. In the past I have had a leaking engine oil seal into the bell housing from one side and a leaking hydraulic pump seal into the bell housing from the other but the engine seal has been repaired. I still have the leaking seal in the hydraulic pump that is causing me to have to drain the bellhousing daily before running. After reading many posts on here, I am wondering if this leaking hydraulic pump seal is related to my engine overheating issue. Any guidance would be appreciated. I have been dealing with this issue for >10 years. Thanks! I have had a couple people come out to look at it but they couldnt figure it out. One guy thought it might be a blown head gasket but it doesn't consume any engine oil and I dont have any air or bubbles in my coolant so I think that is ok. Any ideas? (I have seen some similar issues on here and many knowledgable members chimed in to help. I look forward to hearing from John C. as well as others.) Thanks everyone!
What engine is in there? My PC95 had a Yanmar 3TNV** something or other. What are the temperatures at the top and bottom of the radiator?
Do you have a serial number on this machine. Is it on tracks or a wheel machine? The oil in the damper case is a big problem. I have customers that have pulled the drain plugs out and packed diapers under there in a small pan. The pump will have to come out an the input shaft resealed. The damper and flywheel will have to come off to get to the rear main seal on the engine. The hydraulic pumps could also be overloading the engine. That will take someone who has a lot of time on tune up and troubleshooting.
Regarding the specs: It is a 1993 model with 11,500 hours on it. Komatsu PC90 Serial #1715 Engine: 4D95L-1, Serial #154310 Track machine A mechanic came out to look at it a couple of years ago. He measures the coolant temperature at upper and lower radiator hoses and he said that both the input and output were hotter than he felt was normal, but he didn't elaborate on the exact temperatures. The oil in the damper case has been a problem for a while. We have had it apart to fix the engine-side seal but didn't have any luck repairing the hydraulic side. I figured it would be ok as long as I keep it drained... but is there anything in there that could be damaged or causing the engine to run hot? Thanks!
It's a 1995 year and most likely a US market machine. If you are keeping it drained it shouldn't be the cause of the overheating. If it does fill up and run for any amount of time it will burn out the rear main seal again. You may have a speed sensor that is screwed into the side of the flywheel housing that may be burned out. Usually when that goes bad the electronics default to about 5/8 capacity. Do you know if it is a Dash 5 or Dash 6 model. Can you take and post a photo of the hydraulic pump?
On my PC120-5, I removed the flywheel housing filler plug and installed a hose and ball valve. Could the engine fan be on backwards, reducing its efficiency? Backwards won't change the airflow direction, just lower the efficiency as the blades won't scoop.
Thanks for the response John, all of my documentation indicates that this is a 1993 model PC90-1 with the 4D95L engine. I will try to get a photo of the hydraulic pump tomorrow in the daylight. If the speed sensor was burnt out, would I know it by any indication or operating behavior? It seems to run fine otherwise, but my usage is very infrequent.
Thanks for the reply, I did look at the fan and it appears to be installed correctly. I appreciate the brainstorming here! Please keep the ideas coming! I would love to get this thing fixed so that I can be confident taking it out on jobs again.
Water pump ,temperature gauge or temperature sending unit?
I forgot to mention that we did replace the water pump, but have not checked the gauge or sending unit. I am not quite sure how to check those.
"Nothing HAS improved it"? or has everything improved it? Get a non contact thermometer and tell us what the temp of the coolant outlet from the engine, and coolant inlet from the radiator, and engine block are when it is running as hot as you run it. That might have to wait till next summer, but we can try with the temps you give us now. Also, the air temp going in and out of the radiator. The air temp will be hard to get because you don't want to be anywhere near the spinning fan, but find a piece of painted sheet metal close to the front and back, that should be close enough. What kind of antifreeze and concentration are you running? Has the oil cooler been cleaned to see through it with a light on the other side?
Do you have a monitor panel in the cab? If so take some photos of it as well. Komatsu uses Dash number to denote the build series which can tell us the type of electronics in the machine. The smaller machines were different in that what I recall was the Dash 1 series had the Dash 3 electronics package. My serial number app says its a 1995 which just confuses things more. Komatsu went to the Dash 5 package in the early nineties.
My PC128UU-2 is a 2004. My PC120-LC5 is a 1992. My PC228UU-1 is a 1998. My WA180-1 is a 1988.
Pump from underneith:
That last photo is of the bottom Sorry for the typo, it should have read "nothing has improved it". We have cleaned the oil cooler as well, and running a 50/50 mix of coolant. Unfortunately I cant get the temps for you today, but I will try as soon as I can. Thanks!
Your machine is a Dash 5 model. Under the console on the right side of the operator seat there should be a slotted cutout where you can see the engine control diodes. A green in the middle and a red on each side of the green. Some of those machines had mirrors that tilt out and you could also see the diodes for the machine control computer. If you don't have the tilt out mirror you will need to removed the side panel to reveal everything under the console. Once you get the off you can start the machine and see if there are any flashing codes. Here is a video showing the system on a PC400-5. It works the same way. The computers are just in different places. It is likely the pump is overloading the engine. If you look at the top of the pump you will see some wires going to a solenoid coil on the pump itself. That coil is the TVC solenoid. That can be adjusted to lessen the load on the engine. Here is a video that shows tuning up the pump on the PC400-5. Keep in mind that you have to make sure all the machines systems are working right before ever touching anything on the pump. Good Luck!
Sir, They look like same but they have been a little bit difference!!
.....and LEDs fault code meaning.
Thanks again for the info LACHAU. That PC90 monitor you show doesn't have a machine control computer. It only has a resister that allow current to go to the TVC solenoid in two settings. As I recall the wheeled machines had that monitor panel.
Sorry for my confusion, but does that mean that my PC90-1 doesn't have a machine control computer?
Correct. Your photo of the monitor in your machine only shows the S and L power modes. The machines with a machine control computer will show HO, SO, LO and FO.
Sorry...so sorry Sir; but I should inform that PC90-1 has 02 controllers : one for PUMP and the other for Engine throttle!!!
Attached files are Hydraulic and Electric Circuit diagram in PDF format for more convenience reference.
The other is ENGINE controller.
It does not actively stroke and de-stroke the pumps as the engine load is increased or decreased. Do you see a speed sensor in the schematic? We used to see the same thing in the PW90 machines. The power set switch only has two positions, light load or full load. The TVC solenoid pressure is preset so that the engine can't be overloaded. There are no diodes to indicate faults in the systems. My thought process is the someone turned the screw in a bit or there is something wrong with the solenoid valve. It can probably be tested by running a boom up cycle time. If you are getting boom up cycles at 3.5 seconds or less, the pumps are overloading the engine. Thanks for the schematic! I love that it can be blown up for an easier read.
In this regard, you're right John! But PC90-1 hydraulic control system also has some other functions.
We may go too far!!! Back to main subject is "OVERHEAT". Bobby, Could you inform us about MAX Hydraulic pressure?? A lot of excavator's overheat due to hydraulic pressure set too low!!! Does the machine get OVER-LOAD at heavy load (Engine speed drop down)???