Komatsu D65e-6 overheat

Yep, think i have a handle on how the fluid flows at this point so just a matter of testing pressures at various locations. I figure either my pump is weak or one or more valves upstream are allowing the pressure to drop too much. It seems weird to me that the cooling cicuit would depend on a pressure valve to cool the oil but I am sure there is a good reason for it.

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I have never heard of a thermostat for the torque converter and the valves you are describing sound more like the convertor outlet pressure control. That valve just keeps a minimum amount of oil pressure inside the torque converter impeller, stator and turbine cavities. As I recall it generally ran around 12 PSI at normal operating temperature but could run up to 60 or so when the oil was cold. Problems I have seen are when that pressure is near nothing indicating leakage of fluid getting out of those previously mentioned cavities. The leakage then drops into the torque converter case where a scavenge pump pushed it into the shafts and bearings of the transmission to lube it. Your book should call it lube pressure.

When that leakage becomes excessive the oil fills up the casing and the rotating member has friction against it causing heat. Further compounding the problem is now the oil leakage does not go to the cooler at all and the hot oil is now being pumped directly back into the transmission shafts and bearings hot.

Your are correct about checking your outlet pressure. The book will give you a minimum spec and I can tell you the machine will run with near nothing. You can shim the pressure control and it might help if the pressure is low. I don't think your transmission pump is bad because the transmission is fail safe to go to neutral if there isn't enough flow. The other thing you can check is the torque converter housing has a drain plug on the bottom. After running the machine for awhile you can park the machine and let it sit for a bit. You will need something to hold four or five gallons of oil. Pull the plug and see how much oil comes out of the housing. Normally you should see maybe a gallon. If you get four or five gallons you likely have a torque converter or a scavenge pump that is toast. I've haven't seen much trouble with the coolers except them bleeding fluids into the wrong sides at times. The water sides can get plugs with bits of liner O rings. For some reason the diameter of the O rings is just about the same as the tubes in the coolers and the bits get lodged inside preventing water flow. I seem to remember anything more than 10 degrees drop in temp through the cooler was enough.

Good Luck!

Any reference I made to thermostat was for the cooling system. The problem started as a coolant overheating issue, but that was solved by a thorough cleaning of the radiator. Coolant temps don't get about 180 now. Around that same time I installed temp sensor for the torque converter and discovered that the temp was spiking after about an hour of use. I cracked open the outlet pipe going to the oil cooler and had only a dribble of oil with the machine running, so I know my oil flow to the cooler is pretty low. Tonight I hooked up a gauge at the outlet relief valve to see what the pressure looked like there. The manual calls for 2-3 Kg/cm2 at operating temperature. I started around 6 Kg/cm2 when the fluid was cold and dropped to 3 Kg/cm2 at operating temperature, so I am ok from a pressure standpoint. The other thing that occurred to me tonight is that I have not yet checked the strainer for the transmission. Lord knows this poor machine has had its share of neglect so I doubt the strainer has seen the recommended 1000 hour service intervals. Since I need to drain the fluid for that, I can perform the torque converter fluid amount tests that you are recommending while I'm at it.

Today I performed the converter flood test that was recommended. I only got about a gallon of fluid from the torque converter, but i struggled with the drain plug for bit. I did run the dozer for 3 to 5 minutes just before pulling the plug but never put it in gear or anything. So i am not sure if the test was valid.

Attached are pictures of what i found on the strainers. That is the trans strainer (or lack thereof) on the left. Looks like someone cut it off and just put the end cap and spring back in.

The scavenge pump strainer is on the right. It was moderately clogged but i am not sure it was enough to prevent the pump from doing its job. Either way, I doubt it is going to have much positive impact on the overheating issue.

Zero improvement in the overheat as expected. I am going to experiment with shimming the valve that supplies the cooling loop but I should probably start researching A converter overhaul. Are the parts that cause leakage generally servicable? The service manual lists tolerances for various parts so hoping i can rebuild.

In my experience that amount of oil isn't bad. The red stuff on the strainer basket tells me someone has been in there before. Usually steering clutch covers and such. Any chance a steering brake might be dragging?

I would suggest taking an oil sample next. Usually when the converter is leaking by a lot you will have a real high aluminum reading. The parts that usually go bad are the impeller, turbine and stator. The bearings holding them in place get a little loose and the parts start touching a bit. That is what makes the aluminum in the oil. They are not serviceable. If they touch at all they are junk. Also keep in mind that if you pull the converter you should also pull the cooler and have it checked.

Yea the TC has red rtv all around the perimeter of it so someone obviously took it off at some point. I dont believe I have brake drag because it will keep rolling down an incline in nuetral and i adjusted them to manual specs recently. The shimmed valve didnt make a difference. I am going to recheck the flow to the cooler again today.
I took the intake pipe off of the trans pump and saw something interesting. The oil that was left in the intake port drained through the pump in less than a minute. I dont think a hydraulic pump within tolerances should allow that to happen. I am going to order a new one. If i replace the torque converter i would buy the new pump anyway while i was at it.

You need a large oil flow through the TQ to carry away the heat. You've drained the case as per John C's instruction and only got a gallon out, so although that doesn't completely rule out internal leakage, it kind of suggests that may not be the problem.

I would speculate that because your tranny pump has been running without a suction screen, it's worn out. Even a badly worn gear pump will have no trouble making the lowly pressure a TQ needs, but will not deliver the flow. personally, I would be taking a look at the pump before pulling the torque converter.

Cmark, thanks for the feedback. I am hoping to to have a new pump by early next week. I just replaced the steering pump a few weeks ago due to loosing prime so I know first hand how much difference a good pump can make.
I have been really tempted to see if the new steering pump would bolt in for the trans because they look identical. They are different part numbers though so i guess something is different about them.

Sure would be nice to run the dozer for more than 45 minutes at a time.

I also learned a little about Komatsu price gouging this week. I knew i needed to replace that strainer while i had all the fluid drained. I found it online for $60 but quickest shipping was s2 days. Called the local dealer to see if they had it on hand. I gave him the part number and he told me he could have it by the next day at a cost of $508. I had to make him repeat himself because I didnt believe it. He said he hadnt sold one since 2006....no wonder at that price. Heaven help me if something breaks that doesnt have aftermarket supply.

been there done that with local dealer. track adjuster seals. one seal at dealer cost more the the whole kit after market AND the seal kit parts had the same name as dealer parts

IMO there's no such thing as price gouging, just free market forces at work. All things being equal, if a dealer sees himself losing sales to a competitor with a cheaper price, he will have to lower his price to compete.

Cmark said:

IMO there's no such thing as price gouging, just free market forces at work. All things being equal, if a dealer sees himself losing sales to a competitor with a cheaper price, he will have to lower his price to compete.

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Good point and I'm experiencing a bit of that right now. I've called 4 places looking to order the aftermarket pump. There are apparently none available in the U.S. at this moment. Most are listed around $200, but I've resorted to calling the ones that are listed at $375 to check availability. I guess its all about what its worth to get the part quickly. ;-)

But the Komatsu guy did say he hadn't sold one since 2006....you'd think they would take a hint.

I've found it's always best to Google the part# and look it up on Amazon. Sometimes you can save a bunch of money. That being said I paid $50 extra and $13 in shipping because the local dealer could have a sensor I needed at 8am the next day. Just depends on how bad you need the parts I guess.

I'm having the same overheating torque convertor issues you have except mine only occur when i'm tracking one direction for awhile. I walked it 6KM and had to stop every hour to let the TC cool down. Of course i have those Komatsu Green Good, Red Bad gauges still so i have no idea what temp it was really getting to. When i would do a few turns back a forth on a landing it was fine for some reason.

I still run all the original pumps on mine but did an entire fluid flush of every system before we took it to the bush. i did find excessive build up of grey sludge in my transmission but it didn't concern the HD mechanics that looked at it for me.

My fun ended last week when one of the seals between the final and steer case blew out and now needs to be replaced.

ATCme, that does seem strange. Do you think that the seal that blew out may be somehow related? If you are talking about one of the gaskets between the castings I wouldn't expect those to have any pressure on them. The only variable I have with mine is the harder I work it the quicker it overheats. Even then, its the difference between having to shut it down at 45 minutes verses 1 hour.

I have called like 6 different online aftermarket suppliers trying to find the trans pump and they were all on back order. I'm guessing they must all use the same parts distributor. I finally went to machinerytrader.com and searched for the part number and found a company out of Miami FL that had their own inventory. I paid about $100 more than the going price online but it'll be worth it if it means I can have it running before this weekend.

So have you taken your pump off and looked at it?

jasonharville said:

ATCme, that does seem strange. Do you think that the seal that blew out may be somehow related? If you are talking about one of the gaskets between the castings I wouldn't expect those to have any pressure on them. The only variable I have with mine is the harder I work it the quicker it overheats. Even then, its the difference between having to shut it down at 45 minutes verses 1 hour.

I have called like 6 different online aftermarket suppliers trying to find the trans pump and they were all on back order. I'm guessing they must all use the same parts distributor. I finally went to machinerytrader.com and searched for the part number and found a company out of Miami FL that had their own inventory. I paid about $100 more than the going price online but it'll be worth it if it means I can have it running before this weekend.

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The internal seal that separates the steer oil from the final drive on mine went. There were no obvious signs of leaks on the outside of mine, all internal. I am told it is a common failure. One side of mine was already fixed when i got it. If the seal is gone then most likely the bearing is gone too. I only noticed when i could hear a faint clunk going forwards to reverse. I checked the rear dipsticks and got soaked in oil when i opened one. I don't think mine over heats from this issue. Like yours it will easily roll downhill in neutral. I have an issue with it having trouble moving cold, once hot it moves easily even while idling.

Have you looked at the second strainer in the transmission on yours? Both of mine were clean but my tranny filter was trying to suck fluid through all the goo in the picture i posted above. Once cleaned and new oil was put in there was a definite difference in performance.

I get all my parts through SMS Equipment here in BC. These D65 dozers were really popular in Alberta and i have had zero trouble finding any parts for it. I was going to do my TC pump as well but i have to do the final first before i do anymore damage.