G'day, Have not pulled radiator out of Bobcat before but worked on several vehicle radiators. Pictures to follow shortly. I run the Bobcat running up and down 15 degree hill picking up mulch for about half an hour to an hour. Temp gauge goes up quickly to halfway up normal and then steadily climbs to just on Hot and will go above if I keep operating. On visual inspection the top seam of the radiator appears to be seeping? Photo soon. Is this sufficient to allow to boil? Coolant level is good and coolant pretty new. When stopping and temp is on high you can hear the boiling in the system but no evident overflow. Overflow tank does not get uptake and there is air in top of radiator tank. Hose and overflow tank are sound. Seems like the radiator weeps/seeps/ breathes just enough to start causing this problem. Only weekend hack but was planning on new house site so I need to have it right and don't want to waste the motor which runs fine. Questions - is that weep sufficient to cause the overheating as described? What tricks to getting the radiator out - hydraulic cooler is on top? Would you suspect the water pump? I did tighten belt for water pump inbetween checking overheating. Helped a bit perhaps. Looking forward to wise advices? Regards, MX45.
Should I try Wynns Radiator Seal first??? I have had success other times with this and have lasted many years? Should I just bite the bullet and pull the radiator even if a pain and get it done right? Regards, MX45
If the coolant isn't low, then the problem isn't the leak. That oil cooler looks a bit oily and dusty, I'll bet the radiator isn't getting enough airflow through it, they always look much more plugged up when you can actually see the radiator. Take that oil cooler out of the way and clean the radiator. Or you can check the airflow by measuring the temp drop of the coolant through the radiator when it's in the hot range. Not enough temperature drop in the coolant means there's not enough air flow. Does it cool down if you let it idle? Don't shut it off hot, unless the coolant is too low to cool off.
Coolant is not low. Pulled the cap to inspect on first occasion a few days ago and cap appeared OK and to seal. No evident leak from cap pressure or water. What temp drop would you expect so I can understand? Have temp gun. Regards, MX45
If it's a G Series Bobcat you first need to verify the belt/tensioner for the cooling fan is working properly. If it is, verify (which is not easy to do on these machines) that the thermostat is actually opening and allowing coolant flow. But check that cooling fan belt first.
G'day, thanks for contributing. I just cleaned the radiator and oil cooler from dust and debris - a bit there but not that much. Ran for half an hour. Temp on radiator cap side of tank 41C temp on non rad cap side of radiator ie the RHS was 101C. Let idle and temp dropped from the L on Normal to the A. Turned off and temp dropped on RHS to 90C and rose on LHS to 50C. No bubbling could be heard in cooling system. While standing on the rad cap side of Bobcat can feel the wind externally which would indicate the fan is operating quite well. I previously checked the belt tension on the water pump alternator and it was tightened up as it was a little loose but would not have thought it was not turning the water pump. Does anyone know what temp should be either side of the radiator tanks? Regards, MX45
Any instructions on how to otherwise check the fan belt is tight enough?
I did pull on the tensioner for that fan belt when checking previously and it appeared to not have tensioned the belt but when I checked this time it was working?
Inspected fan belt tonight - easier to see with a torch of a night time. Looks fine = tension is fine. On thinking on probable issues with the radiator cross temperatures looking at 60C difference which is way too much I figure the flow is insufficient. Best place to start is the thermostat - so tomorrow after I have done the first 7 things on the list I will get around to parking the Bobcat where I can service it. Let you know what I find in a few days. Regards, MX45
I would replace the temp sending switch and thermostat regardless .
That's way too much, but it wasn't overheated at 100 so the thermostat should have been open, but might be the issue not opening soon enough or full enough, easy enough to test a thermostat IF you can get it out. If you want, run it until the engine block is 110, and see what the radiator tanks are then. You could also look through the radiator in the dark with a small light on the other side to see through it clearly, that doesn't seem to be the issue anymore though.
fan drive belt has a spring loaded tensioner, it should move freely. make sure your alt belt is tight make sure you have airflow through the radiator and cooler, just because air is blowing out the side doesnt mean it's pulling air through the cooler and radiator. the water pump could be bad, i have seen badly worn impellers and broken shafts, but it's EXTREMELY rare. pulling the radiator is simple, get the hyd cooler out of the way, 2 hoses and 2 bolts (underneath near the muffler) and it lifts out the top. since it's been running hot, i'd suggest when you replace the rad, change out the thermostat and sender. kubota engines dont like to be overheated, it's a sure way to crack the head. bare heads are now running close to $2K
See Below = Pulled drain plug and coolant clean as a whistle. Pulled thermostat housing and pulled thermostat. All photos below are thermostat in 75c, 85c and pretty mush 95c water with no opening at all of the thermostat. Not even with some prodding from my screwdriver. Learned not to get mist on the IR Thermo as it drops the read dramatically. Time for a new thermostat. This one is marked to open at 71C. I am in Sub Tropics. Summer 25 - 40+C = Winter 10 - 20 C generally. Should I just throw away the thermostat and run without? I don't think I have cooked the motor as was running fine and no water in oil or vice versa. Regards, MX45
C series Bobcat.
Put the right thermostat in it. with none, it might run too cold... Sure you could run without, but its always better to run at what the system is designed at. Would make an interesting study, though, take a few readings with no t-stat in it, might still have the over heat problem, and it will lead you to the solution...
Don't run it without a thermostat, most thermostats are designed to bypass when they're closed, and when they open, they close the bypass port. Without a thermostat the bypass is always open. I can't tell from that picture, but just get the same thermostat, or a hotter one if that's what's recommended. 71 is 160 F which is a pretty cool thermostat these days.
Thanks guys, Bobcat thermo about $60A which is exxy considering a standard thermo is maybe $20! Not available until next week. I will run it without thermo as even though it is clearly a fault it does not mean it is the only fault. So knowing time to heat up at current ambient temps and when it got hot I can double check that side of things, radiator condition probably answered by this test. You need a cooler running thermostat over here in OZ - we had long Summer high temps this year. More to come they say. Regards, MX45 - let you know results in comparison with no thermostat in situ.
Again don't over look the temp/heat sending switch .
Will only help you out in the first 15 minutes of operation.. that's not much additional cooling compared to what it will do if you operate the thing year round. Most t stats these days are 180 or higher.
Update = I pulled the radiator hose connected to the thermostat housing and it had corroded to the point of leaking around the hose joint. Could not see that from the engine bay. Anyway re-sealed the radiator hose both ends with RTV and clamps also the thermostat housing less the thermostat. I will put in Radiator Leak Sealant on the test run for leaking/sealing/temperature testing on both sides of radiator and on gauge with current temp sensor in place. I will run for half an hour at least with loads similar to before and give test results. Will wait 24hrs to give sealant strong curing time. Nothing looked that nasty on the inside of the housing or the radiator. Results in a day or two. MX45 PS Biggest problem was wife wanting me to mind my son just after applying sealant with just minutes before it starts to cure and trying to squeeze my hands into these tiny bobcat spaces. Thanks for asking honey!!!!!!!!!!!!!!!!!!!!!!!!
I would never use the sticky tar type radiator stop leak. Solder the radiator up yourself if it's leaking at the seam, unless you can find a shop that still does it.
Ya, I'm not a fan of that stuff either, not like its smart and knows where to go, it just goes everywhere and ultimately would make things worse I always thought. (As in less cooling ability due to coating everything)
G'day Guys, Decided not to wait as Big rain ahead this week. Filled with my sealant and new coolant. Ran for half hour as before on same hill and on flat with larger loads of gravel and not mulch. Took about ten minutes to get to 'O' on normal range and stayed there. So warm up time was the same essentially just did not warm up to the 'A' on normal before & climbing to Hot section. Temp on hot side of radiator 75C = temp on cool side of radiator 70C = small drop would be accounted for with faster flow across radiator with thermostat removed. Let idle - no change. After stop both sides went to 75C. Block temp 83C. Sealant sealed seam in radiator and anywhere else I may not be able to see. Warm day here = high 20's. I share your retiscence about not using chemicals that can seal other small channels and cause issues. However had a Ford 6 cylinder with head leak and this sealant worked for years - started to leak again and renewed sealant - got five years. I trust this particular sealant. Others have been total problems though. I intend to just check my coolant level in main radiator and top up if necessary and continue to use. Regards, Thanks, MX45 = hope the temp figures assist someone one day.
Only other thought I can add to ALL the Wise Words above is to make sure that the Rad Cap is the correct pressure too.. I am not sure on that engine if a few pounds less pressure would be detrimental for any reason, but ' kubota nerds' around here should know for sure.. If it is too high, it will put undue stress on an aged cooling system.. a very well schooled mechanic once taught me that a 12lb Cap instead of a 15lb (where not needed) will stave off issues many times on an older engine.. and NOT having a Thermostat will likely never be a good long-term plan, as any engine LIKES to operate under some amount of 'safe heat' for sure _ Far more Efficient, near the temps of disaster, than not!! Good Luck, and thanks for the updates and info, always looking to learn more!!
G'day, I did not think of that but the radiator cap is 13lb. So on the good side of that range. I have always presumed it is original or the right one? Regards, MX45
And, the other side of that is whether it actually opens up @ proper pressure of course _ undue stress on system if not, and might explain 'weeping areas' if still an issue after all else.. AND, another cheap replacement for sure, once you know what acceptable pressure ratings are for that engine and age!! Thanks again for the Updates, I am smarter again today than I was yesterday.. I think.. Ha!!
13LB was replacement spec on other radiator cap. I will know if this is working as I have marked the overflow tank level and can watch that go up as it warms and then goes down as it cools.