Yanmar 135D operating temperature?

gbart14 · Apr 4, 2018

I have a Yanmar 132D 4WD and am using a Mott 48" flail mower on more or less flat land. The previous owner installed a mechanical temperature gauge with the sensor in the block on the upper left side of the engine near the water outlet. When operating the flail the temperature slowly climbs to 230 and sometimes up to 250F. I then go to a lower gear and the temp drops a bit. However, no water is being pushed out of the radiator. It has not used any water in several hours of operation. The radiator is in good shape and I cleaned out the core fins recently. I used an infrared thermo gun to check the radiator temp and the return line was about 180F. When I pointed it to the same area on the block where the sensor is, it read nearly the same as the temp gauge. I looked through the operation manual and it says the warning light is supposed to come on at 220F. I am thinking the gauge sensor was maybe installed where the warning light sensor used to be. Please advise. Thanks

California · Apr 4, 2018

If you are running the proper percentage antifreeze/water and have the correct radiator cap (13 psi), and it doesn't puke - you're doing fine. I think the thermosyphon (no water pump) models like that, have a boilover warning light that should come on around 240 degrees.

That does sound like a big mower for the little guy. I think you're doing the right thing to back off a little to keep it under 230 degrees.

Winston (or anybody) - do you have the specs for when the thermosyphon models' warning light should turn on?

gbart14 · Apr 4, 2018

Yes, correct cap and running antifreeze as installed by local Yanmar dealer when they went through it. I realize the 48" should be run with higher hp tractor but both the tractor and the mower were free with the house. I have only about 1.5 acres of flat grass to mow. With the 48", with brand new blades and well lubricated with very little friction I usually have it in 2nd or 3rd gear in low setting. If it gets hot in 3rd, I go for 2nd.

winston1 · Apr 5, 2018

Out of the 135/155 repair manual:

gbart14 · Apr 5, 2018

OK, excellent. That gives me a number. I just downloaded that book. I do have the operation manual but all the Operation Manual says is the indicator light goes on when the engine is overheating, stop the engine immediately and determine the cause. So, on my gauge, if I keep it around 240 or below, I should be OK. I have been up near 250F (end of the gauge) and backed off on the speed. I guess I will start my mowing in the lower gear until the engine is fully warmed up and then see where it goes. FYI, everything else is working great including the vintage Mott flail. It looked beat up but lubed everything up and replaced all the blades and sounds like a sewing machine. Thanks for the help.

normde2001 · Apr 6, 2018

Anything above 180-190 is too hot, (at or above 1/2 mark on the gauge). If radiator fins are clear you need to backflush the cooling system. Speed, load and ambient temp should have little to no bearing on your coolant temp.

reb · Apr 6, 2018

There have been many discussions here about operating temperature. I am in the camp that says the manufacturer sets the warning light temperature at about 238 degrees and does not provide a gauge on many models, so temperatures approaching that level are acceptable. Mine ran around 220+ for years until I rednecked an electric water pump on it.

gbart14 · Apr 6, 2018

I think I have this right - without a water pump (from my understanding of the system) the water needs to be at high temperature near boiling in order to move (someone correct me if that is not true). At sea level (14.7psi) or 0 gauge pressure, the boiling point is 212F. However if you pressurize the system to 14psi gauge pressure meaning 14psi above ambient (via radiator relief cap), the boiling point raises to 248F (roughly). Turns out that 248F is the set point (per the book) of the temp warning light from the factory. So, my thinking is that with a pressurized system, you need to be up there in temp to make the water move. If the water does not move, then it heats up and moves. So, it is a self compensating system of sorts. Keep in mind that the water temp I am talking about is taken just as the water leaves the block for the radiator. The temp I have measured via IR gun on the radiator outlet is around 180 returning to the block from the radiator. So, I know the radiator is working perfectly. I am I on the right track here? Thanks

reb · Apr 7, 2018

The water does not have to be at the boiling point to circulate. Just temperature difference is all that is required. The fan will cool the water in the radiator, causing it to settle and the warm water from the engine will rise and replace it.

gbart14 · Apr 7, 2018

OK, right. Got it, Reb. Thanks, everyone for comments.

In response to Normde2001, the temp is above 180 / 190 when driving on the flat with no implements working.

I have watched the radiator return temp carefully and it does not change (around 180F) even when the gauge reads 245F at the outlet in the block. So, I believe the radiator is doing its job. Further, I am not loosing any water and I have checked the oil temp and it is under 200F so, I think if I keep it under 240 or so, I should be good. I do not experience any change in performance at that temp. But, just to be more precise, it would be great to hear from someone who has a factory allowable operating temp and where that reading is taken. It seems to me to not be that important, otherwise the factory would have warnings other than the warning light. The only indicator of over temperature is a light that goes on at 248F.