Jinma 284 Overheating

greg_g · Aug 11, 2005

( Can you please explain to an old engineer how that can happen. )

It's called a bypass hose Harold - that little section of 3/4" rubber hose that's connected to your water pump. When the thermostat is closed, coolant is recirculated through the radiator.

When the coolant inside the engine reaches a temperature sufficient to open the thermostat, coolant from the radiator flows in. When the inflow of coolant from the radiator lowers the engine coolant temp sufficiently, the thermostat closes. That coolant now in the radiator again recirculates via the bypass hose till the thermostat opens again.

Thus, the more time spent in the radiator - the cooler it should be upon mixing with that inside the engine.

//greg//

greg_g · Aug 11, 2005

( Should the fan be closer or farther away from the radiator?)

Again, I can't see your tractor. But typically the fan should be completely inside the shroud.

Forgot to mention that one of my Jinmas had a defective radiator cap. I got a low pressure replacement from AutoZone (7 psi I think) which helped bring the temp down as well.

//greg//

hbaird · Aug 11, 2005

I thought we were talking about having or not having a thermostat .
Harold

Ranch_Hand_Supp · Aug 11, 2005

hbaird, greg g explained how the thermostat / cooling system works and what has to happen to make the cooling system capable of keeping the engine at a safe operating temp.

The only way the system will work and work per design...
It has to have a thermostat. you will get it

Ronald

Soundguy · Aug 11, 2005

Greg and the others nailed it. The comparison to an auto cooling system where you have forced induction of air thru the radiator is a whole different world to a tractor that travels between 1 and 10mph.. in the tractor case.. the fan is the sole source of air movement thrut he radiator.. and that air is the prime heat exchange component for the radiator, aside from some less significant radiated heat inthe form of IR.. etc..

Engines designed with a thermostat need the thermostat... etc.

Soundguy

ToolManRick · Aug 12, 2005

A liquid cooled engine without a thermostat should always run on the cold side. The purpose of the thermostat is to keep the coolant in the engine until it reaches the operating temperature. Running the engine without a thermostat and still running hot is any one or a combination of engine timing, inaccurate temperature gauge, slipping fan belt, coolant passage blockage, radiator pressure too low (mine came with a 15 psi cap), clogged radiator fins or air flow restriction. Unless the coolant is actually boiling I suspect the gauge. 100C is boiling water, but with anti-freeze and a good radiator cap it won't boil at that temp. Is it boiling over?

stroker88 · Aug 12, 2005

your running to many rpms..........try 1st gear high........stay right at 1500 ............your working the engine & not leting the engine work for you........reason i say this .......i was posting the same ? 3 years back..........remember this is a small tractor........also dont run in 4wd or with rear end locked......good luck ...stroke on

greg_g · Aug 12, 2005

( your running to many rpms..........try 1st gear high........stay right at 1500 ............your working the engine & not leting the engine work for you........reason i say this .......i was posting the same ? 3 years back..........remember this is a small tractor........also dont run in 4wd or with rear end locked....)

Disagree. The attachment I uploaded contains the performance curves for the Y385 engine. Look at the Ne curve. You'll note that it is still developing torque until 1700 rpm. Then look at the Me curve. Note that at 1500 rpm, it's barely developed 70% of it's potential horsepower. So working this engine at 1500 rpm fails to take advantage of it's performance characteristics PLUS fails to spin mower blades at design speed. When I still had Y385s, all my mowing was done in either H1 or L3, depending upon terrain. Regardless of which gear, I operated with the tach indicating engine rpms sufficient to produce 540 rpm at the PTO. After taking the previously mentioned precautions, overheating was never an issue.

And I don't see any corelation between 4wd or diff lock - and overheating. The only time I take my tractor out of 4wd is when it's traveling over concrete/ashpalt surfaces. In fact, there are a few places on my property that I must use both 4wd and diff lock simultaneously - without giving a single thought the engine temp.

//greg//

TJW · Aug 12, 2005

Thanks for all the discussion.
I am used to gas engines also, as far as t/stats go. The only difference I noticed was it was a little slower getting to operating temp. I really can't run my tractor in 2wd too much in my field because it is so wet. I only get a few weeks a year to mow it, which is right now. I was also suspecting my radiator cap, I'll try to rplace it. And yes, it does boil over out the overflow hose when it reaches 100. I think a lot of it has to do with air flow, like it has been said, because it operates around 90 under full load with the hood up and lots of air flow.
I don't want to run it under load outside the "green" rpm zone, I agree with the comments about torque. I read the owner's manual and is says that is where to operate.
I think I will also change my oil, since I was running with a collapsed vacuum line for a while in my breather system. It could be thinner than it should be. I'm not sure about timing, that sounds difficult. I'll save that for last.
TJ

bruce1966us · Aug 12, 2005

IMHO I think that if everyone here that has a Chinese tractor were to remove the thermostate, the tractor will not run hot. It will most likely run cooler. If you don't believe it then take your thermostate out and try it! /forums/images/graemlins/grin.gif