643 Overheating - Stumped

[gladiator175]

Morning all I have a 643 that's a little older but was working great. The machine engine seems fine. I haven't seen the engine overheat to the point where smoke is blowing out. The temp gauge was going all the way to hot after running it up and down the street in full throttle. Changed the temperature sending unit and the gauge - same issue. Checked the thermostat, put in boiling water opens fine. Removed water pump spins and looks fine. Good air flow to radiator. Radiator is fins are clean Oil cooler fins are clean 1. I shot the hoses with infrared heat gun and the pipe going to the thermostat housing was may 180. Nothing more. The bottom hose from the bottom of the water pump area. not all that hot either. 2. I put a 3/4" lawn hose into the top of the thermostat housing to see if water flowed through the engine. It did. 3. Prior to removing everything and with temp gauge showing hot I opened radiator cap and shot the antifreeze with infrared. It was well below 150. 4. with engine running and radiator cap open saw no water movement. Not sure if I really would. One thing of note, I have had the reservoir empty for some time...cant see how that would make a difference. Nothing unusual as far as color in coolant or oil. So I'm just stumped.

 

[gladiator175]

Here are some pictures http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190523736_zpshz1ltpl5.jpg http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190555045_zpswdpqtcrr.jpg http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190542216_zpsx4mrufkz.jpg http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190535466_zpsqfaynior.jpg

 

[Hotrod1830]

Here are some pictures http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190523736_zpshz1ltpl5.jpg http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190555045_zpswdpqtcrr.jpg http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190542216_zpsx4mrufkz.jpg http://i1070.photobucket.com/albums/u481/john_hall10/IMG_20161008_190535466_zpsqfaynior.jpg

Don't rule out a faulty gauge.
If the IR gun is indicating 180 at the hottest point, it may not be overheating. Have you checked all the connections going to the gauge? Probably wouldnt hurt.

 

[Hotrod1830]

Don't rule out a faulty gauge.
If the IR gun is indicating 180 at the hottest point, it may not be overheating. Have you checked all the connections going to the gauge? Probably wouldnt hurt.

Just reread your post and missed the part where you tried a new gauge.
get a cheap mechanical gauge and install it in place of the sender and see what temp it is actually running. With the IR gun indicating 180, I still doubt it is actually overheating, but you cant be too carefull.

 

[gladiator175]

Just reread your post and missed the part where you tried a new gauge.
get a cheap mechanical gauge and install it in place of the sender and see what temp it is actually running. With the IR gun indicating 180, I still doubt it is actually overheating, but you cant be too carefull.

Strange though The old sending unit and old gauge read Hot, the new one did the same. I just can't tell if the coolant is even circulating. The sending unit is right in the thermostat housing. Unlikely that they would both be reading Hot and wrong?? The tap for the sending unit is 1/8" How/what kind of mechanical gauge would I get?

 

[Hotrod1830]

Strange though The old sending unit and old gauge read Hot, the new one did the same. I just can't tell if the coolant is even circulating. The sending unit is right in the thermostat housing. Unlikely that they would both be reading Hot and wrong?? The tap for the sending unit is 1/8" How/what kind of mechanical gauge would I get?

Forgot the kubota's used a smaller temp sender. Unlikely you will find one with an adapter that small.
If you dont have coolant circulating, it WILL get hot enough to boil over and you will hear coolant boiling in the block. If you havent heard that or had coolant errupt( violent boil over) from the cap when you removed it, there is still a chance it is not actually overheating. It may be hard to tell if coolant is circulating by removing the cap.
Is the radiator hot all the way across it? Is there hot air coming from it via cooling fan?
I am saying this because you are measuring temp with the IR gun at the thermostat housing and getting 180. If it where actually overheating, I would expect to see a reading well over 200.
Maybe someone here has a repair manual and can give a ohm reading on the coolant temp sender at 70 deg and 212deg.

 

[gladiator175]

Forgot the kubota's used a smaller temp sender. Unlikely you will find one with an adapter that small.
If you dont have coolant circulating, it WILL get hot enough to boil over and you will hear coolant boiling in the block. If you havent heard that or had coolant errupt( violent boil over) from the cap when you removed it, there is still a chance it is not actually overheating. It may be hard to tell if coolant is circulating by removing the cap.
Is the radiator hot all the way across it? Is there hot air coming from it via cooling fan?
I am saying this because you are measuring temp with the IR gun at the thermostat housing and getting 180. If it where actually overheating, I would expect to see a reading well over 200.
Maybe someone here has a repair manual and can give a ohm reading on the coolant temp sender at 70 deg and 212deg.

I have the ohms sheet as it correlates to temp as these are Faria gauges. The ohms reading is pretty much on the money with the temp reading. I'm wondering if the radiator is a bit plugged.

 

[Tazza]

I have the ohms sheet as it correlates to temp as these are Faria gauges. The ohms reading is pretty much on the money with the temp reading. I'm wondering if the radiator is a bit plugged.

The pump looks good, could the radiator be plugged internally?
I don't remember being able to see any water moving when the radiator cap was off.

 

[gladiator175]

The pump looks good, could the radiator be plugged internally?
I don't remember being able to see any water moving when the radiator cap was off.

Tonight I put a garden hose to the radiator, water moved out the other end pretty good. Checked thermostat again and it opens at 180 like it should. I'm wondering if the radiator cap has anything to do with it. I'm not sure there is any pressure being built up. I'm also wondering if not having anything in the reservoir has anything to do with it, which I doubt.

 

[Tazza]

Tonight I put a garden hose to the radiator, water moved out the other end pretty good. Checked thermostat again and it opens at 180 like it should. I'm wondering if the radiator cap has anything to do with it. I'm not sure there is any pressure being built up. I'm also wondering if not having anything in the reservoir has anything to do with it, which I doubt.

I don't think the cap is the issue. The cap is there ro increase the boiling point of the coolant. The higher the pressure the higher the boiling point is.
Even if the coolant level is a little low, it will still be moving around. The cooling system takes a fair amount of water/coolant. So being a little low wouldn't cause it to over heat.
I'd like to get an IR temerature gun and measure the temperature at the thermostat housing. I have found when having power issues, that the temperature gauge will read wrong.
I had a 743 that i put a new gauge into and the temperature gauge was reading high. There was a flashing light on the top, i removed it and the gauge read correctly. The light must have pulled the power down a bit and messed with the gauge. Hopefully this is all that is wrong with yours.
Any gurgling you may hear could be air in the system from being low on coolant?

 

[Hotrod1830]

I don't think the cap is the issue. The cap is there ro increase the boiling point of the coolant. The higher the pressure the higher the boiling point is.
Even if the coolant level is a little low, it will still be moving around. The cooling system takes a fair amount of water/coolant. So being a little low wouldn't cause it to over heat.
I'd like to get an IR temerature gun and measure the temperature at the thermostat housing. I have found when having power issues, that the temperature gauge will read wrong.
I had a 743 that i put a new gauge into and the temperature gauge was reading high. There was a flashing light on the top, i removed it and the gauge read correctly. The light must have pulled the power down a bit and messed with the gauge. Hopefully this is all that is wrong with yours.
Any gurgling you may hear could be air in the system from being low on coolant?

Be carefull using a generic spec sheet from a manufacturer. Bobcat can have those gauges made to whatever specs they want. Trust but verify.
So does the ohm reading at the sender indicate the 180 you measured or higher, like the gauge reads? If it indicates 180, your not overheating.
If memory serves correct, a bad ground will cause a gauge to read higher than it actually should.

 

[Hotrod1830]

Be carefull using a generic spec sheet from a manufacturer. Bobcat can have those gauges made to whatever specs they want. Trust but verify.
So does the ohm reading at the sender indicate the 180 you measured or higher, like the gauge reads? If it indicates 180, your not overheating.
If memory serves correct, a bad ground will cause a gauge to read higher than it actually should.

btw, if you are using straight water, water boils at 212 degree's with no cap on the radiator. If you removed the cap with the gauge in the hot, it should have boiled over.