Overheating

   / Overheating #1  

BurningBushFarm

Silver Member
Joined
Nov 23, 2010
Messages
133
Location
WNC
Tractor
YM2000D
I can't find the post I thought I just posted. :confused:

Bush hogged today. :) Fun.

Problem: Temp light came on after about 20 minutes. :(

Before going out we had cleaned the screen in front of the radiator, blew out the air filter, and the level of the radiator water was fine.

Came back inside and checked the manual and this forum.

Will check flow @1500 rpm. Will flush it out.

Any other suggestions?

Thanks.
 
   / Overheating #2  
If what you do doesn't work, check the thermostat. The temp light will have a sending unit, that might be bad. Does the engine seem hot or is the red light simply on?
 
   / Overheating #3  
If the overheating is real you may notice a burned smell. Don't open the radiator cap, that's the same as opening a pressure cooker! The top of the radiator shouldn't be to hot to touch for a moment unless you were running it real hard.

Incidentally these need to be run at good speed, over 1800 rpm or preferably over 2000 to circulate coolant through the radiator when working hard. Pushing it hard at low rpm will cause overheating.

I bought this little Harbor Freight infrared thermometer on sale under $10. Various parts of the radiator and engine show different temperatures but I've never found the radiator over 200 or the engine head over 250 except maybe right at the exhaust manifold. This can verify if you simply have a bad warning light sensor.

This model Yanmar doesn't have a thermostat.

One test you can perform is: with the engine cold then mid-warm, look in the radiator for bubbles (engine running) which would indicate a head gasket leak (or less likely, cracked head). Exhaust leaking into the coolant will overheat it quickly. This might be accompanied by loss of coolant too, but not necessarily. You should see water circulating, showing that the water pump is ok, but not bubbles.

If there is any question of losing coolant be sure to spin the engine before starting using the compression release, to blow any water out of the cylinders since water is incompressible.

It isn't unusual for these 30 year old tractors to have a plugged radiator. A radiator shop can likely rod it out, or a new radiator should be under $300.
 
   / Overheating
  • Thread Starter
#4  
I was making sure I was running at ~ 2400.

I was in 5th, but then went to 3rd the second time out after I read about making making sure I was moving enough coolant through the radiator.

If there is no thermostat what triggers the temp light?

Thanks for the Harbor Freight tip.
 
   / Overheating #5  
A thermostat is a temperature-sensitive valve just before the upper radiator hose that holds water in the engine until the set temperature, maybe 170 - 190. Then it opens to let the coolant reach the radiator. But these old Yanmars don't have one.

The warning light sensor is an electrical switch that closes around 235 degrees warning of imminent boil-over.

And the radiator cap is nearly identical to a pressure cooker regulator - it holds pressure until 13 lbs. This allows up to some 240 - 250 degrees coolant temperature, still liquid, before it boils and spits out the coolant. Engines run more efficiently at higher temperatures.
 
   / Overheating #6  
You should post your model # on every thread. The YM2000 runs notoriously cool, about 160*, and with all things right, should never overheat.
I have a Ym2000B, with a factory temp gauge, and the first tool to go in my toolbox was a whisk broom. When mowing, as soon as I see any rise above normal on the gauge I know it is time to clean the rad screen. It normally never reaches the 1/4 mark.
 
   / Overheating #7  
After years of brush mowing, the actual passages thru the radiator can become plugged. Even though we have the same debris screen, every five years or so I have to remove the radiator from the tractor and carefully hose out all passages. Huge difference.
Mike
 
   / Overheating #8  
If what you do doesn't work, check the thermostat. The temp light will have a sending unit, that might be bad. Does the engine seem hot or is the red light simply on?

Have not read all posts so forgive me if i repost this.

Your tractor does not have a thermostat.
 
   / Overheating #9  
You have a problem, there is no reason to overheat at this temperature unless you have an issue. I would second a head gasket proble, maybe, or most likely a blocked radiator which basically means that only part of it will be cooling right with correct flow. Another thing is make sure your belt is not slipping, it needs to turn the same speed as the crank pully not be slipping causing the waterpump to turn at a slower speed.
 
 
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