I have a Grey market excavator. It is a MM55sr and in many ways similar to a Cat 305. I have had an overheating problem and it works for about an hour with full rad all fluids good until percolating into overflow tank and hitting red line very quickly on heat gauge. I always shut down immediately and wait 2 hours for cool down before refilling rad which seems in working order. I have no collapsed hoses, fan belt tension is good and I have removed thermostat hoping for cooler running but still exactly same problem. I am moving towards the water pump now but before I do that does anyone have a take on this that may assist me? I have tried to throw into the forum by circulating MM55sr manuals and diagnostic material I have. Exhausted info I have from them. I appreciate the info I get here. Thanks from farmerboy.
It has a Mitsubishi KN 4 cylinder diesel. My trouble shooting path will be water pump > head gasket but I wait for your feedback.
Have you tried flushing the radiator/engine with water? What is the history of this machine? age? hours? when did this overheating start? has any hard water been added? and how long have you owned it? First put the tstat back in, they usually close off the recirculation back through the engine when warmed up. Kinda rare for a water pump to not pump. Have you checked the radiator temps at the top and bottom hoses? Can you see clearly through the radiator from the front to back? Pretty common to get a good mat of junk built up between the oil cooler and radiator, and still have both of them look clean. If the radiator is plugged for airflow the temp going in and out will both be high and close together, if the radiator is plugged internally (or the pump isn't working, or you're thermostat is MISSING) the top of the radiator will be hot and the bottom will be much cooler when the engine is fully hot. The radiator will also be hot on top and cool on bottom if the thermostat is just opening but that doesn't mean anything is wrong. Seems a little odd that it will go a full hour before overheating, can you check the actual temp coming out of the tstat at different points to see if the temp is gradually climbing? and let it idle for a bit to see if it cools down at 30 minutes after startup and every 15 minutes after. edit: Also, any change in the hydraulic functions when it gets hot? I'm still looking for something other than head gasket...
If you can get hold of a heat gun check the temp difference between the inlet hose and outlet hose in the radiator. Should be about 12 DegF or so.
Thanks for your replies Delmer and Nige. I have flushed rad less than 100 hours ago. Overheating started 10 hours ago. The machine has been in my hands for 3 years and has about 3000 hours on a rebuild diesel. We live in a soft water area so hard water not a problem. Rad space between oil cooler cleaned out. I will be trying to borrow a heat sensor gun and proceed. I appreciate your inputs. All the best form farmerboy.
Start at the simplest first. Have you worked on anything else shortly before that? What has changed right before this happened: work conditions, ambient temps, fuel issues, hydraulic issues, operators, etc.? Next, I don't think your water pump is gonna crap out all of a sudden, but possibly it overheated and cracked the head or blew a head gasket.
My Mitsu water pump cost me 700$, it never stopped pumping, just didn't pump enough. Before changing it run the acid rad flush crap in a bottle, that stuff scares me but it did help BEFORE changing the water pump. Mine would only overheat in the summer at full load. Mine went out while paddling a barge so there was no shutting it down, I cranked the heat, idled it down, and started sweating.
I am self taught and just getting brave enough to throw big wrenches. I also am able to admit making a mistake. I had a heavy duty mechanic here to look at things and give me some suggestions and he tested the belt and said it was fine. It may have been my mistake that he was referring to the condition of the fanbelt and not it's tension. I took that to mean that the tension was fine and went on to greater things he suggested. It now seems obvious when I pulled on it today that the belt is slightly loose and that may be my problem. I am at the end of my tensioning arc and am going to replace it with a smaller belt properly tensioned. If that fixes it I will let you know. I will also remember to retension it after a bit of a run in if it seems slack. It has been a good lesson on checking the simplest things first MYSELF. Humbly yours, farmerboy.
Hi farmerboy, I see you said that you cleaned the junk out from between the oil cooler and radiator, did you actually remove one or other of them to do it? I find it's the only way to go so that you can pressure wash them properly and make sure all the fins are clean, as Delmer said they can look clean when they're together. I hope the belts are your problem it's always good when it's something simple. Cheers.
The adventure continues. Changed to 15 series 395 fanbelt which is half inch shorter than the 400 and that gave me a lot more latitude in tensioning. Problem is only slightly better. First thing in am I am taking apart rad and oil cooler and good cleaning. Will do a rad flush at same time and take to rad shop for comments. Looking for a heat sensor gun and have enlisted the help of my good friend, "The Grand Master". Solutions will come if we apply ourselves (his knowledge and my knuckles**. All the best from farmerboy.
When you get the radiator off look inside as well as you can at the tubes. Look for solder bloom that may be closing the tube openings. Solder bloom is corroded solder that looks just like rust on steel except it will be gray in color.
Actually, you should let a hot engine run at idle for a spell before shutting it down, allow the fan to cool the hot coolant somewhat. Immediate shut down will allow temps to continue to rise risking head and cylinder liner damage. In these cases I typically yank the radiator and take it to a radiator service shop, have it either cleaned or core replaced as needed. Even if it's not your problem, you know for certain you now have a good radiator that will serve you trouble free for some time.
I once had a trackhoe do something similar and it drove me near crazy, till I finally found an exhaust leak that was blowing into the radiator, longshot, but something quick I check on all of them now.
Thanks to all who replied. I have a rebuilt rad now and there were blooms in it as suggested by Tinkerer. I will be following the advice of Atco about idling before shutdown and look into mitch504's idea about exhaust systems. One other thing I will be doing is removing and cleaning the fuel tank as I was passing a lot of rust thru my filters after using additive Cfoam. I intend to coat the inside of tank with non rusting tank material. I appreciate the level of information here and learn a lot. All the best from the farmerboy.
Thanks also to you for taking the trouble to report back about what you did to solve the problem. Too many times on here a thread sort of peters out and nobody gets to know what the final fix was.
I see the forum working that way, it is at it's best when people do follow up and be worthy members. I have tried to pass on pdf files of the MM55sr manual and some diagnostic service charts. Most of it was freely given to me by reefermike and I pass it on. Thanks to all those who throw big wrenches as I am a curious apprentice. All the best from farmerboy.
I have a kobelco 120 and had a overheating problem.i replaced cleaned took apart everthing I could think of,but found in the crankshaft pulley there is a clutch set up for your fan. mine was slipping net allowing the fan and water pump to turn properly.has anyone ever heard of that????
I agree with Nige, thanks for the follow up. :notworthy
Welcome to HEF morrbub. :drinkup That's a new one for me. :beatsme
thanx, a hard item to remove, eat your Wheaties, noticed it while watching the engine run and wondering ***? the fan slowed way down and I didn't change the rpm.i first thought a loose belt ...but srarted exploring and found that little jewel , I wondered how many other machines were built like this and how many people were chasing ghosts in the cooling systems? its easy to look past it
Ah, fan clutches. Happy daze when all D10R's were so equipped. A total PITA to both troubleshoot & repair.
yep, took me a week of fornicating fido to find the problem.im not even sure how it works, it bolts on the crank and must be similar to a centrifigal clutch,im no better a mechanic than a speller!!!!
I need information on Mitsubishi MM30SR Mini Excavator. I was older post where you help others. Do you still have the information. I am desperate.