Thermostat

[rorschachtested]

I recently got a 642B and am trying to clean it up and make everything right as I'm working it pretty hard. I'm kind of overheating. I stop before it actually reaches hot but my over flow tank keeps filling up and I wait until it cools and put the coolant back in the radiator. This is starting to get time consuming. I have already flushed the system and replaced the coolant. So next I want to replace the thermostat. I checked and there isn't one in there. Napa said to bring them the old one to match it, I can't do this because I don't have the old one. I checked the part # 6632614 on Google and nothing. I guess I need to know is this a very specific part that I need to get from Bobcat or is there a hundred thermostats in any auto parts store that will fit? I was also wondering if the grease zerks are standard, as I have to replace a few of them? Sorry this is all pretty new to me as this is the first time I actually bought a machine as opposed to renting. Thanks, Jeff

 

[OldMachinist]

The 642B has a Mitsubishi 4G32 1.6L engine. See if they can look up the thermostst if you know the engine. The Dodge Colt and several other automobiles used the same engine if they have trouble looking it up by engine. The grease fittings are standard.

 

[Fishfiles]

The 642B has a Mitsubishi 4G32 1.6L engine. See if they can look up the thermostst if you know the engine. The Dodge Colt and several other automobiles used the same engine if they have trouble looking it up by engine. The grease fittings are standard.

what about cleaning the external air passages (fins) of the radiator , did you do that , there should be a set of covers that can be removed from inside the engine compartment and clean the radiator from the bottom side also

 

[Tazza]

what about cleaning the external air passages (fins) of the radiator , did you do that , there should be a set of covers that can be removed from inside the engine compartment and clean the radiator from the bottom side also

You mention you have to put the coolant back into the radiator, are you sure its not combustion gas forcing the coolant out? If you are running coolant, it should have anti-freeze/anti-boil additives. It shouldn't boil unless its over heating badly.
This is where a non contact thermometer is very handy.
As there is no thermostat installed, it has to be a radiator/water pump issue.... Or the engine could even be running lean causing it to run hot.

 

[rorschachtested]

You mention you have to put the coolant back into the radiator, are you sure its not combustion gas forcing the coolant out? If you are running coolant, it should have anti-freeze/anti-boil additives. It shouldn't boil unless its over heating badly.
This is where a non contact thermometer is very handy.
As there is no thermostat installed, it has to be a radiator/water pump issue.... Or the engine could even be running lean causing it to run hot.

Actually when this happens and I turn off the ignition, the engine runs-on, and I have to pull the choke to stop it. Would that be a sign of running lean?

 

[OldMachinist]

Actually when this happens and I turn off the ignition, the engine runs-on, and I have to pull the choke to stop it. Would that be a sign of running lean?

I know the Mitsubishi engine in the 742B had a fuel shut off solenoid on the carburetor to prevent run on. That's the first place I'd check if it has the solenoid. It's supposed to shut off the fuel to the main jet when the key is turned off. If it doesn't have a solenoid then it could be carbon build up in the combustion chamber causing a hot spot and with the alcohol in the fuel these days it doesn't take much of a hot spot to cause it. Winter blend fuels when used in the summer are also a cause.

 

[jerry]

I know the Mitsubishi engine in the 742B had a fuel shut off solenoid on the carburetor to prevent run on. That's the first place I'd check if it has the solenoid. It's supposed to shut off the fuel to the main jet when the key is turned off. If it doesn't have a solenoid then it could be carbon build up in the combustion chamber causing a hot spot and with the alcohol in the fuel these days it doesn't take much of a hot spot to cause it. Winter blend fuels when used in the summer are also a cause.

I doubt that the thermostat not being in there has anything to do with the overheating. Most engines without a thermostat or one stuck open will run cold instead of hot. lean mixture, timing or head gasket leaking may do it though.

 

[rorschachtested]

I doubt that the thermostat not being in there has anything to do with the overheating. Most engines without a thermostat or one stuck open will run cold instead of hot. lean mixture, timing or head gasket leaking may do it though.

That makes sense. I've checked for oil in the coolant or coolant in the oil numerous times, and all looks well, so hopefully not the head gasket. How do I tell if its running lean, and how do I remedy it?

 

[Tazza]

That makes sense. I've checked for oil in the coolant or coolant in the oil numerous times, and all looks well, so hopefully not the head gasket. How do I tell if its running lean, and how do I remedy it?

I don't know how its done properly, but what i do with mowers etc is the smell of the exhaust. You get to know the normal odor, when it smells a little fumey its too much fuel and there is another when its lean. Its really hard to describe.
I'd start with ensuring you have water moving enough. Even that your temperature sender is working properly. Check temoeratures first, see if it is actually boiling water.
As for coolant in the oil, or oil in the coolant, this means nothing. If the crack or leak is between the combustion chamber and the water jacket there will be no oil in your cooling system, you will just get exhaust gases. I had a kubota like this. It didn't use and oil, no water in the oil, on oil in the water. It had cracks from the combustion chamber to the water jacket, it was filling the overflow bottle if the machine was left on a slope when warm.

 

[rorschachtested]

I don't know how its done properly, but what i do with mowers etc is the smell of the exhaust. You get to know the normal odor, when it smells a little fumey its too much fuel and there is another when its lean. Its really hard to describe.
I'd start with ensuring you have water moving enough. Even that your temperature sender is working properly. Check temoeratures first, see if it is actually boiling water.
As for coolant in the oil, or oil in the coolant, this means nothing. If the crack or leak is between the combustion chamber and the water jacket there will be no oil in your cooling system, you will just get exhaust gases. I had a kubota like this. It didn't use and oil, no water in the oil, on oil in the water. It had cracks from the combustion chamber to the water jacket, it was filling the overflow bottle if the machine was left on a slope when warm.

Well I've always wanted one of those non-contact thermometers, now I have a good excuse to tell my wife why I need one. I'm heading off to Florida to visit my parents so I guess I'll start tearing into this when I get back. Thanks to all for the insight so far.

 

[Starkiss 773]

Just a quick thought Hows is the Radiator cap it needs to holds pressure you can test it if the cap dosent hold pressure it will dump coolant to the overflow tank when unit gets to temp.Just my 2cents worth.