hitachi 225 overheating only under load

This topic contains 9 replies and was last updated by daniel-figueiredo 8 years 6 months ago
July 9th, 2013 2:59am
I'm working on a Hitachi 225 that only overheats under load. I have cleaned all of the screens, radiator, condensor. This seems to help but the machine only is able to load one trailer before it overheats. The machine has 7980 hours it is a 2004 model. I have also replaced the thermostat since the radiator cooling fan never stops working. Now I don't know what to check, since no coolant is consumed I can't call an EGR cooler to replace even it has one, also it does not overheat instantly elemenating the chance of the water pump being the issue. The radiator seems to be working ok since there is a big temperature drop. Only thing that comes to mind is possibly a head gasket in need of replacement, or an electrical problem like coolant sensor or actually the gauge malfunctioning. At this point I don't want to guess at the problem since it can get expensive too quickly. If anyone knows anything on this series of excavators I am very grateful to your help.
July 9th, 2013 6:59am
It sounds like you have done some good troubleshooting so far. How do you know you have a large temperature drop across the rad? Are you using a heat gun? How much temperature drop do you have? If you have a heat gun I would advise you to verify the coolant temperature at the sensor location (usually near the t-stat housing) to make sure the gauge is accurate. Also use the gun to take measurements in and out of major components such as the oil cooler and cylinder head to determine if you might have any restrictions to coolant flow. A large temperature drop across the radiator indicates that the air flow thru the rad is fine, but could also indicate that the coolant flow thru the rad is insufficient. You may need to load the machine down while testing to re-create the conditions. If your water pump is belt driven make sure it isn't slipping as well. If you are still stuck after all of this check water pressure by plumbing a 0-100 psi pressure gauge at the outlet of the water pump. Rev the engine to high idle and record the pressure. I'm not sure of the spec for that engine but I would expect to see 20 psi at a minimum if the water pump is working properly.
July 9th, 2013 11:19pm
Thanks for the feedback. I have no heat gun i just grapped the hoses by hand and noticed that the temperature coming out of the upper rad hose is alot lower than the lower rad hose. The water pump is driven by belt and it does not slip. When I check the temp at the oil cooler, cylinder head the temp should be very to the temp of coolant going back to the radiator. If any of those components temperature is way off that will indicate they need to be replaced right.
July 9th, 2013 11:37pm
If you do have a heat gun, does it have a remote probe, if so insert it into coolant to verify coolant temp, also it is very important to hold gun as close as possible to component being checked, IE top and bottom goose neck of radiator to verify temp drop, do not shoot top metal goose neck and then bottom rubber hose, readings will vary greatly, also are you sure that it is a coolant overheat, I am not very familiar with hitachi but it is possible that overheat warning in cab may be for hydraulics, a weak or broken spring in relief could create alot of heat and not adversely affect performance if excavator is not being run hard, that said check fan speed and if this is a computer controled engine and pump, pull speed sensor at flywheel and look for damage, I hope some of this helped!
July 9th, 2013 11:44pm
Sorry, i just saw your latest post, the top hose should be hotte4r than bottom, but checkingby hand is not very accurate or SAFE, you only have two hands, please take care of them now if bottom hose is hotter than top, was the fan belt changed recently and possibly routed wrong to make water pump turn the wrong way, seems like a simple problem but have seen it before, fan should blow air from engine side through radiator, help yourself out in the long run and invest in a good heat gun, it will simplify alot of problems. GOOD LUCK
July 10th, 2013 6:43am
Robert is right. I would also be more concerned with the fact that the upper rad hose is cooler than the lower rad hose. It should be the other way around. I would start your investigation there. Check with the operator of the machine if anyone else has been working on it recently. Sometimes these sort of details get left out when talking to an operator who is frustrated.
July 11th, 2013 1:12am
I must admit that the thought of a fan belt turning a pump the wrong way never occurred to me. But it is a centrifugal pump; if it is turning, it will be slinging water, maybe not as much or not as efficiently, but it cannot move water the wrong way. Like Jbone says, the upper hose should be hotter.

However, regarding the thermostat, a lot of diesel engines have a long body thermostat that must be present for the bypass water flow to work properly. With the wrong thermostat in the housing, the water will be continuously in bypass and not be forced through the radiator as it should be.

A second thought I have is that if it has a mechanical injection system, and the timing advance is not functioning. When under load and speed the engine could be running late (retarded) causing it to overheat when working hard. You would require a magnetic pick-up and an electronic timing light to diagnose this.
July 11th, 2013 9:38pm
Sounds like a water flow issue, large temp drops of more than 10 to 20 f usually mean not enough coolant is flowing through the rad.( general specs most systems are designed to drop 10 -15 degrees across the rad once at operating temp) Just cause the belt is turning the right way does not mean the pump is moving water. I have seen may impellers slip on the shaft internally.

Hot water will not flow out the top rad hose if there is not flow and heat will build in the system from the lowere rad hose up into the radiator.
July 13th, 2013 4:36am
Well here's hoping that Daniel gets it figured out, and that he reports back to us what he eventually found. Way too often guys do not let everyone know when and what was done.
July 16th, 2013 2:22am
thanks for all of the great tips. The reason why I didn't get back so soon was wanted to make sooner that the problem would not come back. I finally get to look at the excavator when it was acting up. I checked the temperature at the upper rad hose and at the lower rad hose. The temperature at the upper hose was reading 150 degrees fahrenheit and at the lower hose it was reading around 130 degrees fahrenheit. At that moment I knew I couldn't call the water pump. Then took a closer look at the machine and found debris build up on the inside of the tracks. I asked the operator where did the come from and he told me it came from the pit. I went to check the pit. There I found a lot sawdust and fiberglass insulation everywhere, and a lot of dust in the air. Then I looked at the CAC and radiator and there was the answer to problems. I found in between the CAC to the radiator build up sawdust and fiberglass stuck on the radiator fins. So basically what I did was I blew it out with an air blower all three components. I asked that the operator of the equipment to blow out the condensor, radiator, and CAC at three time intervals before he starts the day, half way through their shift and before the end of the day especially if it happens to rain overnight. I told him to do that a few days if the engine continues to overheat while doing the cleaning service I'll have to replace water pump. After a few days the operator calls and tells me that the engine does not overheat, and all along it was the work environment was causing all of the problems.

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