Bobcat 773G Turbo Overheating

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clintrobbins

Active member
Joined
May 28, 2009
Messages
36
My 773G Turbo overheats after several minutes of operation. The temperature rises slowly but doesn't stop rising till I shut it off. The coolant system is full, I tested the thermostat (starts opening at ~160 F and is fully open at ~190 F), I adjusted the drive belt and get a lot of air out the side grills, the engine oil level is correct, and both hydraulic reservoirs are full. Does anyone have suggestions on what could be causing the overheating?
 

salsllc

Member
Joined
Jun 5, 2006
Messages
9
are you sure its overheating? turbos run extremely hot that why you have to let them cool down before shutting it down. is your engine oil overheating? you are using engine oil to lube and cool the turbo....check on that first.
 

mrfixitpaul

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Joined
Mar 28, 2009
Messages
365
are you sure its overheating? turbos run extremely hot that why you have to let them cool down before shutting it down. is your engine oil overheating? you are using engine oil to lube and cool the turbo....check on that first.
Have you checked that the radiator is clean....it's under the oil cooler
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
Have you checked that the radiator is clean....it's under the oil cooler
Mine the temp guage is cafuey, have change the sensor, computer and the guage panel and still, after a couple hours the guage will begin to float up and down, ( it moves too fast to be warming and cool of that much that quick, say every 10 seconds) often getting to the yellow, and ocasionally to the red, causing a shutdown. I have installed a standard guage in the machine and the temp is rock steady on the new guage.
I would install a separate guage to see if you really have a temp problem or just a guage problem. So far the only cure for mine has been to unplug the sender in the summer months and pull the glow plug relay (glow plugs cycle 30 seconds if there is no signal from the temp sender.
If you have any sugestions I'm all ears.
Sometime the spring loaded fan belt tensioner becomes frozen and the belt gets loose and slips at higher rpm resulting in a slow fan speed and over heat. The air coming out the two side vents should almost blow your hat off if flowing properly.
Ken
 

Land-Tech

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Joined
May 13, 2008
Messages
160
Mine the temp guage is cafuey, have change the sensor, computer and the guage panel and still, after a couple hours the guage will begin to float up and down, ( it moves too fast to be warming and cool of that much that quick, say every 10 seconds) often getting to the yellow, and ocasionally to the red, causing a shutdown. I have installed a standard guage in the machine and the temp is rock steady on the new guage.
I would install a separate guage to see if you really have a temp problem or just a guage problem. So far the only cure for mine has been to unplug the sender in the summer months and pull the glow plug relay (glow plugs cycle 30 seconds if there is no signal from the temp sender.
If you have any sugestions I'm all ears.
Sometime the spring loaded fan belt tensioner becomes frozen and the belt gets loose and slips at higher rpm resulting in a slow fan speed and over heat. The air coming out the two side vents should almost blow your hat off if flowing properly.
Ken
I've had problems with the sensor, If its telling you its hot and you know it not its easy to check.Or like ken said the guage. Scott
 

m610

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Joined
Apr 1, 2006
Messages
173
I've had problems with the sensor, If its telling you its hot and you know it not its easy to check.Or like ken said the guage. Scott
Don't forget to check the fan/gearbox and belt. I just fixed a 763 that was overheating due to a bad gearbox and smoked the belt. A new gearbox and belt fixed the problem.
 
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C

clintrobbins

Active member
Joined
May 28, 2009
Messages
36
Don't forget to check the fan/gearbox and belt. I just fixed a 763 that was overheating due to a bad gearbox and smoked the belt. A new gearbox and belt fixed the problem.
Update with the solution: After checking everything else, my last step was to flush the radiator. Although the coolant tank was full, I added the flushing liquid to the radiator and found that it took a few quarts to top off the radiator. While flushing, I found that it didn't overheat while working it for about an hour. So, I started watching the coolant and found that when the coolant warmed up, it expanded into the coolant tank as it should. BUT, as it cooled, it didn't return to the radiator - so the coolant tank eventually filled up and started spitting coolant out of the coolant cap vent. I then discovered that the radiator cap gasket between the radiator and atmosphere was shifted to one side and wasn't sealing. Therefore, as the coolant cooled and should have been returning to the radiator, it was sucking air instead! I ordered a new radiator cap but, in the meantime, I shifted the deteriorated gasket into the correct position and that solved the overheating problem.
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
Update with the solution: After checking everything else, my last step was to flush the radiator. Although the coolant tank was full, I added the flushing liquid to the radiator and found that it took a few quarts to top off the radiator. While flushing, I found that it didn't overheat while working it for about an hour. So, I started watching the coolant and found that when the coolant warmed up, it expanded into the coolant tank as it should. BUT, as it cooled, it didn't return to the radiator - so the coolant tank eventually filled up and started spitting coolant out of the coolant cap vent. I then discovered that the radiator cap gasket between the radiator and atmosphere was shifted to one side and wasn't sealing. Therefore, as the coolant cooled and should have been returning to the radiator, it was sucking air instead! I ordered a new radiator cap but, in the meantime, I shifted the deteriorated gasket into the correct position and that solved the overheating problem.
Glad to hear it was a minor problem, Mine is getting worse, going to try removing the sender from the tstat housing and just letting it dangle in the wind near the engine, perhaps glow plugs will still function near normal this way, if it gets a little heat from the motor. Putting a standard 2" temp guage back in the hole. When the stock guage shows hot pulling the trottle baack to a idle will drop the temp just about as fast as the revs come down. Almost like it is feeding back form the rpm sensors or alternator, I at a loss.
Ken
 

Kbolster

Member
Joined
Sep 22, 2014
Messages
8
Mine the temp guage is cafuey, have change the sensor, computer and the guage panel and still, after a couple hours the guage will begin to float up and down, ( it moves too fast to be warming and cool of that much that quick, say every 10 seconds) often getting to the yellow, and ocasionally to the red, causing a shutdown. I have installed a standard guage in the machine and the temp is rock steady on the new guage.
I would install a separate guage to see if you really have a temp problem or just a guage problem. So far the only cure for mine has been to unplug the sender in the summer months and pull the glow plug relay (glow plugs cycle 30 seconds if there is no signal from the temp sender.
If you have any sugestions I'm all ears.
Sometime the spring loaded fan belt tensioner becomes frozen and the belt gets loose and slips at higher rpm resulting in a slow fan speed and over heat. The air coming out the two side vents should almost blow your hat off if flowing properly.
Ken
Hey Ken, Im having the problem of the fan belt loose causing over heating. Could you explain how I can tell if I need a New fan belt or a New tensioner. The belt is extremely loose. How do i tell if The tensioner is stuck?
 

Bobcatdan

Well-known member
Joined
May 3, 2012
Messages
1,684
Hey Ken, Im having the problem of the fan belt loose causing over heating. Could you explain how I can tell if I need a New fan belt or a New tensioner. The belt is extremely loose. How do i tell if The tensioner is stuck?
The tensioner is spring load and can be moved relatively easy by hand. It is pretty common they rust tight.
 
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