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  1. #1

    Default Kubota B-7100 Help - Coolant Blowoff ????

    My kubota 2X4 HST is having some trouble.... Within 5 minutes after start-up it starts to blow cooling fluid out the overfill tube. It then will spit out coolant every so often... especially when mowing thicker grass... I have checked coolant levels and looks fine. Unlike previous usage, today, light smoke was coming from the breather from the engine... definately oil related.... This has me assume that this is beyond a coolant issue!?!? I need help in diagnosing... I'm not the sharpest tool in the shed so I will defer to the experts here... I've decided tractor to stay in garage until repairs are made.. don't want to do any damage... HELP ME PLEASE...

    Thanks ahead of time... [img]/forums/images/graemlins/laugh.gif[/img]

  2. #2
    Elite Member
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    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Lots of questions here. You say it keeps blowing out coolant, yet the coolant level looks fine? What's keeping the coolant level up, oil? Check for oil usage and blown head gasket by removing rad. cap and looking for bubbles in coolant when running cold. Smoke coming from the "breather". Is that the air cleaner or the crankcase vent tube?

  3. #3

    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Thanks for the reply... The coolant level is lower... just marginally so.... I have replenished each time it blows off.. But by no means is all of the coolant exhausted and there is no coolant whatsoever... I have operated it only 10hrs or so with the blow off from the coolant overflow tube (this only happens once in a while - Maybe once every 15 minutes of use)... But during this last hour I noticed light discharge (smoke) from the tube from the engine (more oil smelling)... This really raised the red flag... and I immediately stopped... Thanks for any advice... Ted.

  4. #4

    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Went out and checked the tractor and located the tube that has the light oil smelling smoke coming out. The tube originates out of the top of the engine. Oil level looks good. It registers at the top of the fill line... Really full. Looks normal no unusual colors other than really black (needs a change). [img]/forums/images/graemlins/crazy.gif[/img]

  5. #5
    Elite Member thcri's Avatar
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    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Did you try a new radiator cap. Most radiator caps have a pressure spring in them for when they do get hot, them springs can go bad and they will allow the cooling system to loose all pressure and then your fluid gets a boiling and then will run out the tube.

    Just something to think about.

    murph

  6. #6

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    2001 TN65, 1951 8N Ford

    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    You're not overfilling it, are you? A cooling system without an expansion tank needs an inch or so of expansion space below the top of the radiator. If you fill the radiator all the way to the top it'll push coolant out when it gets warm until it has that space.

  7. #7
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    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Maybe you don't have a problem. You didn't say it was over heating, and if, with no coolant recovery bottle you are only losing minimal coolant, and a little smoke out the breather tube, (that's what it's for), sounds pretty normal to me. I would flush the cooling system, change the rad. cap and change the oil and see what happens. If no coolant bottle, I would add one. That was a great invention.

  8. #8
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    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Captain TedStriker
    The B7100 doesn't have a temp gauge and overheating is signified by coolant blow by with a whistle sound. Mowing think grass (use low gear) could cause overheating and that would explain the coolant loss. You need to check and make sure that your radiator is not clogged up, use compressed air to blow out the debris in the fins. Get a manual to tell you the hot shut down procedures and you should be OK. Hope this helps.
    Lewis

  9. #9
    Platinum Member
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    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Hi,

    Let me say that you do have a problem. Hopefully a MINOR problem, but note it could be serious. My B7100 had all of the symptoms that you describe, and mine turned out to be serious.

    (1) Cooling System. I know that I sound like a broken record on this board, but if I can save an engine or two then it is worth it to me. The B7100 has a "thermo-siphon" cooling system; it has no thermostat or water pump. It is a good design, but a lot of people have problems with it because it is different from normal automotive cooling systems. The thermo-siphon system works because of the natural fluid flow that occurs as the coolant heats up. However, it is CRITICALLY important that no more that 50% antifreeze be used in the coolant (per the owner's manual instructions). Having too much antifreeze stops the natural coolant circulation and an overheated engine will result. It is also very important to keep the radiator clean.

    Note: The B7100's alternator is mounted behing the fan in a way that makes it look similiar to a water pump. If you have doubts as to whether it is a water pump or alternator, note the electrical wires going to it, and also note the lack of any thermostat bypass hoses.

    (3) Blowby. The smoke coming out of the valve cover breather tube is called blow-by. On my B7100 engine that had overheated, the compression rings went bad on two of the three cylinders, allowing cylinder pressure to blow by the piston and into the oil pan, and then through the oil passage ways into the valve cover and out the tube. The blow-by first manifested itself as light smoke, then heavy smoke, then oil dripping out of the tube, then oil pouring out of the tube.

    (4) Whistling Overheat Warning Device: This is a simple design that takes advantage of the coolant overflow tube exhaust to activate an attached whistle to provide an audible warning of an overheat condition. I have seen some (newer?) B7100s that have the whistle installed, but most of the B7100s that I have seen do not have installed.

    You need to minimize engine operation until you correct the overheat condition. Then hope damage to the engine hasn't been too great.

    If I can help any further, let me know.

    Kelvin

  10. #10
    Super Star Member Egon's Avatar
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    Default Re: Kubota B-7100 Help - Coolant Blowoff ????

    Kelvin Has said it all.
    Maybe drain/flush cooling system and fill with just water for test run. If the Rad pluggs up on the outside it'll overheat if working hard.
    Is the fan belt tight and does the fan turn? Mine had a seized dynamo and very quickly overheated.

    Egon

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