843 over heating

[Crash734]

Hey guys, so I purchased this 1990 bobcat 843 about 3 months ago and it has been a work in progress since. It has the isuzu 4jb1 motor. When I purchased it not one of the gauges worked. Well as of right now it has all new gauges that seem to be functioning properly. Now that the temp gauge is actually reading, it seems to peg the gauge after about ten minutes of running wide open. I replaced the thermostat, and the temp sending unit with one physically identical from the auto parts store. I also pulled the inspection plates to see the oil cooler and there were a few mouse nests. So I hosed those out along with the radiator fins to hopefully clean any dirt and debris out. Also noticed the the coolant hose on the right which goes to the thermostat housing gets very hot while the other seems to stay cool. Not sure how to check the fan but with it running in higher rpms, I can feel it blowing air out of the right side of the radiator behind the exhaust tip but I can't feel any air coming out on the left side. Feel like I should be concerned about that. Still having issues with the gauge maxing out. Any recommendations on where to start next?

 

[foton]

if the upper hose is hot the lower cold,(since you replaced the thermostat) I think it is time to check the flow of the radiator and relook at the side that seems to have restricted air flow. BTW did you replace the thermostat with something around 180 degree F.? does it overheat at a idle or half throttle?

 

[Crash734]

if the upper hose is hot the lower cold,(since you replaced the thermostat) I think it is time to check the flow of the radiator and relook at the side that seems to have restricted air flow. BTW did you replace the thermostat with something around 180 degree F.? does it overheat at a idle or half throttle?

The new thermostat is rated at 180* and the temp rises very slowly at idle but fast enough at half throttle where I can sit there and watch the needle climb

 

[foton]

The new thermostat is rated at 180* and the temp rises very slowly at idle but fast enough at half throttle where I can sit there and watch the needle climb

by chance have you checked to make sure there is no exhaust gas making it into the cooling system, there would be a lot of turbulence from a blown head gasket, I think this would be a slim chance of happening without any other problems. kinda takes me back to the radiator having a restricted flow.

 

[Crash734]

by chance have you checked to make sure there is no exhaust gas making it into the cooling system, there would be a lot of turbulence from a blown head gasket, I think this would be a slim chance of happening without any other problems. kinda takes me back to the radiator having a restricted flow.

I have not, how do I go about checking that? So today I've been doing nothing but working on it. Pulled the radiator off completely and hosed it out, seems to have good flow. Also took a wire brush and some degreaser to the oil cooler cause it was pretty gunked up. Also while looking around, I noticed that the fan shroud that goes around the fly wheel has a broken piece that is completely missing, maybe two inches wide by maybe 6 or 8 inches tall and it's right where there air intake is under the cab on the left side of the machine. I don't know how to upload a picture to show you haha. Not sure if that's big enough to cause any issues, feel like it's not seeing how fast the temp gauge rises. Haven't fired it up yet to see if cleaning the coolers fixed it yet, waiting for it to dry so it doesn't fling all the wet gunk back onto it that I washed off. Also got my hands on a laser IR temp gun so I will check the thermostat housing to make sure it matches what the gauge is saying. Also, the antifreeze seems to look as if its brand new concentrated, it is extremely green haha.

 

[Crash734]

I have not, how do I go about checking that? So today I've been doing nothing but working on it. Pulled the radiator off completely and hosed it out, seems to have good flow. Also took a wire brush and some degreaser to the oil cooler cause it was pretty gunked up. Also while looking around, I noticed that the fan shroud that goes around the fly wheel has a broken piece that is completely missing, maybe two inches wide by maybe 6 or 8 inches tall and it's right where there air intake is under the cab on the left side of the machine. I don't know how to upload a picture to show you haha. Not sure if that's big enough to cause any issues, feel like it's not seeing how fast the temp gauge rises. Haven't fired it up yet to see if cleaning the coolers fixed it yet, waiting for it to dry so it doesn't fling all the wet gunk back onto it that I washed off. Also got my hands on a laser IR temp gun so I will check the thermostat housing to make sure it matches what the gauge is saying. Also, the antifreeze seems to look as if its brand new concentrated, it is extremely green haha.

So I fired it up and took it for a test drive. Definitely does not heat up as fast as it did, but it is still pegging the gauge. Based off of the laser IR gun, the hottest spot I could find on the thermostat housing read 198*F. So realistically I don't think it is actually over heating based off of that. Would you agree? If that's the case, what would cause the gauge to max out like it does? I'm stumped seeing how it's a new gauge and a new sending unit, unless the sending unit from the auto parts store doesn't have the right resistance values?

 

[Wayne440]

So I fired it up and took it for a test drive. Definitely does not heat up as fast as it did, but it is still pegging the gauge. Based off of the laser IR gun, the hottest spot I could find on the thermostat housing read 198*F. So realistically I don't think it is actually over heating based off of that. Would you agree? If that's the case, what would cause the gauge to max out like it does? I'm stumped seeing how it's a new gauge and a new sending unit, unless the sending unit from the auto parts store doesn't have the right resistance values?

My experience has been that "physically identical" only means that the sending unit will plug the hole and the wire(s) will plug in to it. Electric gauges function best with the specific sending unit they are designed for.

 

[foton]

My experience has been that "physically identical" only means that the sending unit will plug the hole and the wire(s) will plug in to it. Electric gauges function best with the specific sending unit they are designed for.

I think your best bet is to get a new complete temp package with gauge and matching sending unit, I think your stuff is mismatched. but 198F is about has hot as I would want it to run at. IMO , about the exhaust entering the cooling system it would be blowing some coolant from the radiator cap unless the cap was replaced with a higher psi one to keep it from happening. bad ,but seen it.

 

[foton]

I think your best bet is to get a new complete temp package with gauge and matching sending unit, I think your stuff is mismatched. but 198F is about has hot as I would want it to run at. IMO , about the exhaust entering the cooling system it would be blowing some coolant from the radiator cap unless the cap was replaced with a higher psi one to keep it from happening. bad ,but seen it.

about the anti freeze check it, if someone did not cut concentrate to 50-50 that would make it run hot it needs water to transfer the heat properly. the anti -freeze is to raise the boil-over temp. and to protect from freezing and some water pump lubricant's. but water does the heat transfer.

 

[rodbuilder]

No doubt about it - if ypu have "air" (otherwise know as COMPRESSION gasses) coming out of the radiator the engine has a bown head gasket or cracked head.....or BOTH!! It's not just a thermostat because a bad thermostat isn't going to allow compression to leak between the water jacket and the cylinders - which is what's pushing the water out!!\\Remove the cylinder head and take it to a reputable automotive (head/engine) machine shop and have them magnaflux it. Ahead CAN be welded and rebuilt but it will also need to be resurfaced to make sure it's 100% flat. Add one head gasket set and you'll be good to go! DO NOT USE ANY SEALERS ON A HEAD GASKET. ANYONE WHO TELLS YOU TO IS AN IDIOT!!!

 

[rodbuilder]

IIt has NOTING to do with the antifreeze mixture. BALONEY!!! A more than 50-50 blend of antifreeze will NOT make an engine run hot, it will lessen the antifreeze's ability to protect the engine from freezing in super-low temperatures. It has NOTHING to do with keeping an engine from running hot.

 

[Skookum98]

Having the same problem, with also fluid only travelling out of cap to reservoir as well. If head gasket was leaking would there not be signs of that in the oil? (There is not oil looking clean and level is always fine)