I have owned this machine about 7 years now and with the exception of a small hydraulic leak i have had zero issues with it until now. I was feeding the other day when it started steaming bad luckily i got it shut down before it overheated and i got to looking and it blew the small coolant hose running from the thermostat housing to the head. I replaced the hose and the leak was fixed. i refilled the coolant making sure to go through all the steps to insure the cooling system didnt get airlocked and everything seemed to be going fine until i ran it to feed again and it started to heat up on me and upon shutting it down it sounded as though the coolant was boiling in the radiator. My guages all work properly and it didnt get to hot so i believe the head and head gasket are fine. Im thinking the thermostat is stuck shut and was trying to get some further opinions on it. Would a stuck thermostat result in that hose blowing like it did? Any help would be appreciated. Thanks
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OldMachinist
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Stuck thermostat is what I was thinking as I read your post.
7LBSSMALLIE
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alt belt runs water pump, give a visual
The thing is, if the thermostat was bad, it should read as overheating on the gauge.....
I was even thinking radiator cap causing higher than normal pressure.
I'd run it for a little bit to get up to temperature and look in the overflow bottle, look for bubbles. If it continues to bubble, it is a head or gasket, it may just be air trapped in the system making the noises.
I think i got it figured out i worked on it for 8 hours the other day went through the whole cooling system from top to bottom i found the thermostat didnt want to open also the upper radiator hose was bad. I replaced both and tested the temperature gauge and found that it wasnt working properly as well. After i found that out i decided to replace it with a manual gauge and also to add a oil pressure guage. Filled the sysytem with coolant ran it a while and it never got hot so i think its remedied.
One thing with temp gauges on bobcat, if it runs out of coolant, the sender won't read right and the gauge won't move.
For about 30 bucks a infrared thermometer makes it a lot easier to track temperature trouble down. Especially with thermostat trouble.
i went totally away from the bobcat gauges and installed some aftermarket gauges for all other than fuel level. I added an oil pressure and let me say a guage with an actual reading beats a dummy light anyday!
I probally changed 2 thermostats on Bobcats since 1976 and would bet once it really didn't even need a new one ------- it is really easy to test the thermostat if you have it out already , pry it open enough to insert some dental floss or thread thru it , tie that to a stick or large spoon , hand it off the bottom of a pot with water on the stove with a thermometer in it , boil the water and when it falls off the spring note the temp , the number should be on the thermostat at which it opens , probally like 190 degrees F (if memory serves me right ) I have found the most common problem for a 753 running hot is the cooling fan belt stretched out or the plastic pulley gets worn along with the belt width worn down and the belt goes farther down into the pulley making the tension looser ,bad motor mounts will affect belt tension , second most common would be an externally clogged up radiator and or oil cooler , seperate the cooler from the radiator and blow air thru all the fins and see whats amount of dust you throw up , if the machine has been run on water and not coolant then and internal blockage could be the problem , a bad or wrong psi radiator cap will cause problems and the aux hydraulics sticking on will run it hot fast also --------------753's had a low coolant level sensor on the radiator -------------------
