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

ToolManRick · Aug 13, 2005

Bingo! The cooling system would be defective if it ever reached operating temperature without a thermostat, unless there's really something else wrong or it's 160 degrees F outside. /forums/images/graemlins/smile.gif

Harrygoodwrench · Aug 13, 2005

I have to side with Bruce, & Toolman on this one. The engine should run cooler with the thermostat removed providing the rest of the cooling system is functional. The only purpose for a theromstat is to allow engine to achieve operating temperature asap and maintain it there for maximum efficiency by modulating the flow. This results in max power output & effiency, longer engine life, etc.
I have worked on hundreds upon hundreds of gas & diesel engines of road design, stationary units as well as marine design and although their cooling sysems may differ they all do the same thing. A tractor is much easier in design.
BTW, the main purpose of the bypass hose system is to permit coolant flow between the block and the suction side of the water pump when the thermostat is closed to provide uniform warming of the block during warm-up. True there are some that may circulate it thru a heater core then the radiator as the bypass but that is only primarilly for the passenger heat.
In my opine removing the thermostat will make the engine run cooler assuming all systems are working properly.
I believe the poster having the overheating concern has a problem in another area. Some areas of concern: clogged radiator fins(maybe internal passages), block/head cooling passages sludged up, defective water pump as in impeller bad or belt slipping. Hose collapsing(lower radiator hose)Head gasket leaking some combustion gases into coolant, radiator cap, intake or exhaust restriction, timing, airflow over radiator. These are just some areas that I thought of quickly at the moment and there may be others. Always check the easy first I always say.
I would first suggest to the poster to verify with a known temp gauge what the temp really is.

greg_g · Aug 13, 2005

( the main purpose of the bypass hose system is to permit coolant flow between the block and the suction side of the water pump when the thermostat is closed to provide uniform warming of the block during warm-up)

I stand corrected Harry. I was considering the bypass hose from the wrong side, and see now that there's no circulation path through the radiator available when the thermostat is closed.

//greg//

Harrygoodwrench · Aug 13, 2005

Greg, others,
I must differ. What you see during warm up with thermostat installed and closed is turbulance due to the water pump impeller attemting to circulate the coolant. The by-pass in effect is only designed to allow circulation of coolant while thermostat is closed.
Many engines will actually overheat if not "burped" or vented after refilling the cooling system. Thats why some manufacturers provide a vent hole(very small drilled hole or a jiggle pin) in the thermostat face to provide circulation to vent air.
Of course the thermostat is necessary as we all will agree but a engine will run cooler with out one which is not desirable due to we want all metals to expand to operating temperture so maximum efficiency can be achieved.
I have run many an engine at part throttle RPM for quite a while( 1/2 hour) after rebuild with a heat enchanger consisting of nothing more than a water pump pipe connected to the water pump inlet and the discharge was dumped overboard and the engine and engine would run cool. It was the increased coolant flow that caused the decreased temperture as Hbaird stated in a earlier post.
I am not trying to prove anyone incorrect I am only trying to inform those interested in the purpose and design and reason of such components. Simply put, if you slow down the media flow then heat transfer will decrease. Its simple physics.
With all said, if the gentlemans concern still exists with the thermostat removed his problem lies elsewhere and not with the thermostat. Most likely I would assume would be clogged/plugged radiator tubes.
As I said, I respect all here but am trying to help a poster solve his problem.

TJW · Aug 14, 2005

Latest Update. Went to the farm an mowed.
Changed the oil, adjusted the shroud again.
Still runs hot. I was able to mow with the hood up, but as the day got towards noon and heated up, I had to stop when I went in the red and cool off. The furnace filter is really catching a lot of stuff. Maybe my field is just too much on the first cutting.
I didn't mention, but about six months ago I lost the belt without knowing and it boiled over while idling and I wasn't with the tractor. It was hard to start before then, I would think because it was still breaking in, but now it starts easy.
I don't know if I possibly damaged something when it overheated?
I still need to try the radiator cap, but after that I'm out of ideas.
TJ

greg_g · Aug 14, 2005

( still need to try the radiator cap, but after that I'm out of ideas. )

Sounds like you haven't gotten around to removing the radiator for a proper cleaning either. Ain't no way you can tell by looking at an installed Jinma radiator to see whether or not your air gun or water hose did any good.

//greg//

pasturesnew · Aug 15, 2005

Good morning,

For what it is worth:
I'm running a new 254T, cutting bramble scrub and tall grass on steep slopes. It has been 28-35C in the shade and I am having to use 4x4 and low 1st or 2nd to keep it safe.

The only time the temp guage goes above 80-90 is when that radiator screen gets blocked - and then the temp rises very quickly unless I do something about it immediately.

I carry a small auto vacuum with me, powered from the cigar lighter. Takes about two minutes to pop the hood, take out and tap the screen, vacuum the radiator and put it all back again. I leave the engine running if it has got above 90 - if that screen is blocked, it will not cool down sufficiently for a safe shutdown. With the cleaned screen, by the time I am back in the seat the temp has dropped to 80 and of we go again. Also, I always give it another clean with the shop vac before putting it away.

Not an elegant solution, but hope it may help.

bluechip · Aug 15, 2005

I didn't carefully read this whole thread to see if anyone suggested this, but a bad head gasket could cause overheating. Especially if the engine got very hot when the belt broke. We have a liquid that changes color with CO but you MAY be able to see if you are getting bubbles in your coolant before you get to 100C (boiling).

Somthing is not right here...

Wayne_Freeman · Aug 15, 2005

Bluechip is right about the head gasket causing overheating. I had this happen on my first Jinma. It would slowly run hot and all the suggested fixes recommended here did no good in solving the problem. The symptom for this however is you slowly lose liquid in the radiator. To diagnose this problem simply fill the radiator, leave the cap off, start the engine and observe the liquid for any sign of bubbles. If it bubbles you have a leak in the head gasket! When you pull the head and observe the gasket footprint the area that has leaked will be obvious. Performing this fix would probably require a 102 mechanic. A 101 mechanic like me would have a 50/50 chance of doing it right the first time in my opinion!

TJW · Aug 15, 2005

I don's see how I could look for bubbles in the radiator. The circulation is so great with the engine running that I wouldn't be able to see any bubbles. I guess that's because I took the t/stat out. I thought about the head gasket also, hoping that it wouldn't come to that. I'll look for the CO detector fluid and a radiator cap. Thanks for all your help. I only get to my tractor on the weekends so I won't be able to give you an update until Saturaday night or so...
TJ