Jinma 284 overheating - thermostat part number?

[nepa]

Hi folks. For the past week I have been cutting hay with my 2004 Jinma 284 with Y385 engine just in mornings and evenings. For four days the engine has been running at 80 degrees until last night when after just a little running the temp shot up all the way in the red. The belt is tight, the antifreeze was up to level, and the radiator was clear of debris or chaff (which I use my air compressor to clean after each running). I have used this tractor for 8 years, but only 350 hours. I figure that the original thermostat is the likely culprit. Is there a common part number that I can pick up locally? Will I need too make my own gasket to install it? I do not believe the problem to be the head gasket because if that much exhaust gas was blowing into the cooling system, then I think that there would have been a lot of antifreeze shooting out of the overflow while it was still running. The overflow did not shoot antifreeze until I turned the overheated engine off. Thanks for your help. Part numbers please.

 

[Rich Waugh]

I don't have a part number or you, as the people I know who have replaced theirs just took the old one to NAPA and found a fit. The important thing is to get one that not only has the right temp rating, but also the proper low pressure rating - these tractors use a 'stat that is rated at about 5-7psi, not the usual 14psi of modern cars. If you put in the higher pressure stat you may blow the water pump seals or the radiator.

First though, I'd seriously clean the radiator. Not just blow it out with a compressor (which, by the way, can bend the fins over), but use a hose and really get the chaff dust out of all the fins. That ldust gets pasted on there like dried mud. I used to do it your way with an air hose and overheated my engine once - then I learned to clean it with a hose and haven't had problems since.

 

[nepa]

Thanks for the reply Rich. I tightened the belt a little more this morning, just in case, but could not go 200 yards before the temp gauge started climbing quickly toward 100. There are no indications of head gasket failure. I am still thinking thermostat, and would still want part numbers from anyone who has replaced it with success. Thanks.

 

[RonMar]

Rich, I think you have thermostat confused with radiator pressure cap. Thermostats do not have a pressure rating, they open and close based purely on their temperature. The pressure cap on the other hand determines the system pressure in the coolant system and opens and closed based purely on system pressure to vent to the overflow.

I have been cleaning radiators for years with compressed air. The only radiators I have ever seen damaged during cleaning were damaged WITH WATER, specifically from a high velocity nozzle. The mass of the water at speed will hammer the fins to **** and fold them over. Other than rinsing it off lightly to flood the passages, which I then blow clear with compressed air, the only real effective way to clean a rad with water IMO is to remove it and immerse it in a tank of rarm soapy water and let it soak... AN effective way to gauge how clean a radiator air passages are, is at night or in a darkened garage. Place a light on one side and look at the light from the other side. A little hard to get light behind the shroud, but this will give you an idea of how clear the passages are. Are you running a screen filter in front of the radiator? The holed plate that came with mine, i wrapped in common aluminum window screen. this is very effective at catching the fine stuff before it wedges it's way into the air passages.

i made up a wand out of an aluminum arrow shaft that allows me to reach nearly all the rear face of the radiator to blow the chaff back out the front, the way it came in.

As to your problem, first thing I would do is pull the thermostat and inspect it. Then put it in a pan of water on the stove and raise it's temp to it's rated temp and above and see if it opens. If not, there is your problem. You could also re-assemble the tractor without the thermostat to see if your symptoms change. Without the thermostat, you can also gauge pump flow by looking into the top of the radiator when you start the engine...

Good luck.

 

[greg_g]

Nothing special about it. Just ask (NAPA) for a standard tractor thermostat, 80 Centigrade (175 Farenheit). Wouldn't hurt to change the pressure cap too, its another standard NAPA item; tractor type/7 PSI. And seriously, chaff is a big problem for these Chinese radiators. Go into an area where you can control the light. Loosen the fan shroud and pull it back pears the engine. Use a flashlight to find all the places that light doesn't come through to the other side. You'll be surprised. Some have even has to pull the radiators for a proper soaking.

The advice to avoid both pressure washers and compressed air is sound. Once completely clean, you should in the future clean the radiator with a low pressure (<50 psi> garden hose. That way you don't have to worry how many PSI your air compressor is hitting that cheap Chinese aluminum with. I for example have a 175 psi compressor. I used it for other radiators (American/European) without issue, but would never consider it on a Chinese compact tractor

//greg//

 

[Rich Waugh]

You're absolutely right, Ron - minor brain malfunction there. Obviously I know better, but you sure wouldn't know it from that post! (grin) Thanks for straightening that out, it could have confused someone not familiar with the things.

 

[quicksandfarmer]

Removing the thermostat and running without it would quickly tell you if that's the problem.

 

[Bob Rooks]

Removing the thermostat and running without it would quickly tell you if that's the problem.

Not necessarily so. I have stated this many times before but my voice is getting hoarse from it. Here is another read from the web:

"The engine is cooled by relatively cool coolant returning from the radiator. The heat capacity is directly related to the product of the flow times the temperature difference between the cylinder head (where the heat is mainly generated) and the returning coolant. When the system is working right the thermostat starts to open when the head gets to the thermostat temperature, say 190F. A stream of hot coolant at almost 200F reaches the radiator and the radiator loses the heat proportionally to the difference between the air temperature and the coolant temperature. That is the critical part: if the air is 100F and the coolant is 200F, twice as much heat is cast off as it would be if the coolant is 150F. Without a thermostat to keep the radiator inlet temperature as high as practical, the radiator can't get rid of heat as fast as it should. When the system becomes saturated with overheated coolant, which is common if the thermostat is removed, the engine is overheated."

In short, don't run without a thermostat, but you will do as you will.

 

[greg_g]

Removing the thermostat and running without it would quickly tell you if that's the problem.

I agree with Bob. Depending upon ambient conditions, running this particular engine w/o the thermostat can actually make it run too cold.

//greg//

 

[Rich Waugh]

Yep, the cooling system is engineered to perform its function and all the parts work together to achieve this. Radiator (heat exchanger), thermostat (regulator), water pump (circulator) and coolant (exchange medium); each has a specific function in the workings of the system and each is necessary for the system to function as designed. The thermostat is there to maintain the proper thermal differential for heat abstraction to occur efficiently and taking it out of the system changes the rate of heat abstracted. At higher ambient temps, removing the thermostat can therefore cause the engine to run too hot. As Greg noted, if the ambient temp is low enough, running without a thermostat will cause the engine to run too cold, and that's also a bad thing for diesel engines. Diesels want to be running at their designed heat, usually around 180-190°F (~80-85°C) - below that and there are problems with condensation in the oil, inefficient combustion, excess soot formation, etc. Above that temp and lubricants break down, tolerances creep, etc.