Kubota Thermo Syphon Cooling question

[SteveM]

I have a 78 B6000E with thermo syphon cooling. Last night while mowing in cool temperatures, steam began blowing out the overflow valve. After a quick idle and shutdown, steam blew at high pressure for 2 minutes. After some time to cool, I inspected the radiator (no leaks, fan belt fine) and refilled with water. Tractor started and ran fine for 5 mins to get it back in the barn.

1) Could this have been caused by a low water level in the radiator? (havent checked level in a while)
2) What is the proper water/antifreeze mix for upstate ny winter use?

Thanks for your help!

 

[MJB]

I think that a low level would likely cause the thermo-siphon system to not function properly. I usually use a 50/50 mix of water and antifreeze for winter use here in central New York. Due to the different rates of thermo-expansion between water and anti-freeze, thermo-siphon systems work better with more water than anti-freeze in the mix. I would probably go with a 60/40 water to antifreeze mix on your tractor. I would also drain and flush the cooling system to be sure that the passages in the engine block and radiator are clear. Hope this helps.

 

[Chris99320]

Steve,

I have a mid 70's L185 with the thermo syphon. I would say there are a couple things that would cause the overheating. Low fluid level in the radiator would certainly cause the system to overheat. The cold level should be ~1/2 from the top of the radiator. If the level gets below the inlet for the upper radiator hose water will not circulate. I check mine almost every time I fire her up.
I use a 50/50 mixture in mine year around. We have 100 degree temps in the summer and low teens in the winter.
The second thing to check is for good airflow through the radiator. Keep the screen in front of the radiator clean and occasionally clean out the fins of the radiator with water or air.
Something else that my L185 has is a whistle on the overflow tube. When steam is released it twirps. It starts as an occasional twirp so you know you are starting to run hot. For me it almost always means I need to clean of the radiator screen.
So give the cooling system a good flushing, filler up with fluid and check the level and screen often.

 

[WVBill]

Do you happen to know what the Kubota Part number for the whistle on your overflow tube is? My '78 B6100 doesn't have one and if I ever get it hot, I'd rather hear a whistle than see steam as an over heat warning!

 

[Chris99320]

WVBill,
The whistle was on the L185 when I got it and is described in the owners manual. I imagine a Kubota dealer could look it up.
I will try to look at my manual and the whistle tonight to see if I can spot a part number.

 

[njrqs]

My parts manual is hard to read, but the part number could be.......

15021-7204-0

I have taken mine off and blown into it and it make no noise at all so suggest it doesn't work well.

Fortunately I can see it when seated so could see any steam escaping.

I also check my water level each time as I don't like the thought of another cooked engine after spending $7000 AUS on the engine in my truck !!

Yes also keep that screen really clean !!

Cheers

 

[Turfman]

Ok, Neil, what in US dollars is 7000 AUS? For 7000 US i'd buy a new truck!

 

[njrqs]

About half that so approx $3500 US.

Tell me about it. I wished I had but like all good repair jobs it cost heaps more than it was supposed to !!

 

[WVBill]

Thanks for the part number. I'll get my dealer to order one for me.

 

[SteveM]

Thanks everyone for the pointers. I would like the board's opinion on the best way to flush the radiator, and which antifreeze brand (if it matters) i should be using. I have half a recent bottle of GM antifreeze - would that work?

BTW last night I filled the radiator with 100% water and ran it without incident for about 30mins...looks like it was the coolant level.

Thanks again