Overheating 743B

[94BC743]

Hello all, Long time lurker here and finally made an account because I'm stumped. About a month ago I bought a 94 743B with 4500 ish hours. It needed a few hydraulic hoses and fuel return lines. I never really ran it for more then 1-2 minutes until about a week ago. The original temp sensor was broken along with the original gauge. I replaced the sensor and gauge with a universal temp gauge. I've done some digging on this forum and found the common head cracking issues with this motor so id like to get it figured out. The motor starts up fine and runs great, good power, oil is clean and stays at the same level, the coolant level stays right at the "full level". The coolant temp steadily rises from 100 to 230, at idle it doesn't get much above 200, but at 1/2 to 3/4 throttle the machine will go right up to 230 degrees and I shut it down. I have replaced the radiator, water pump, coolant and tried it again. With no change, the machine still will raise right up to 230 degrees in about 20 minutes. I have a IR thermometer and the thermostat housing will be 220-230 degrees at some points, the radiator hoses are at around 190 degrees. In a last ditch effort I removed the thermostat as I figured that was the last thing it could be. No change, it still goes to 230 degrees. I have heard some motors can overheat without a thermostat so iI ordered a OEM one and it will be here Sunday. The radiator cap seems to be working fine as the over flow tank will fluctuate and the system does build pressure. The radiator/oil cooler are clean, and the fan seems to be working fine as I can feel plenty of air moving around. Any ideas?!!

 

[foton]

the only thing I can think of is a blocked coolant passage in the engine , unless you have a blown head gasket or cracked head.

 

[Nitro7402]

I had a similar issue with my 743, I believe my biggest problem was the oil cooler was plugged full of dirt and oil and was not letting air flow thru. I also pulled my thermostat, and changed the water pump. changing the pump was easy, fairly cheap and allowed me to get a since of the condition of the water passages. The old pump seamed ok, but it was leaking from the weep hole, the fins on the newer one were slightly different, not sure if that help the efficiency of the pump, but the combination of everything fixed my overheating issues.

 

[Tazza]

I had a similar issue with my 743, I believe my biggest problem was the oil cooler was plugged full of dirt and oil and was not letting air flow thru. I also pulled my thermostat, and changed the water pump. changing the pump was easy, fairly cheap and allowed me to get a since of the condition of the water passages. The old pump seamed ok, but it was leaking from the weep hole, the fins on the newer one were slightly different, not sure if that help the efficiency of the pump, but the combination of everything fixed my overheating issues.

If you're not getting bubbles in your radiator, i'd think your head is not cracked, but have an issue with coolant flow, be it a bad water pump or blocked radiator not being able to get enough heat out of the coolant.
Your inspection panels are in place on the blower housing right? the ones you remove to gain access to the oil cooler?
Without a thermostat, your temperature should never get that high.

 

[94BC743]

If you're not getting bubbles in your radiator, i'd think your head is not cracked, but have an issue with coolant flow, be it a bad water pump or blocked radiator not being able to get enough heat out of the coolant.
Your inspection panels are in place on the blower housing right? the ones you remove to gain access to the oil cooler?
Without a thermostat, your temperature should never get that high.

Update for this issue, I left the machine for a while and just recently started working with it. After looking at some parts diagrams I found what my inspection panels should look like in my blower housing and I had none. After replacing them all is good. Machine runs up to 170ish degrees and stays right there. At times it might get 180-190 if its real hot outside and i'm working it at full rpms but other then that it says cool. Thanks everyone!