# overheating kubota



## mrkeith (Jan 25, 2006)

oops.....sorry in advance for the double post 

hi, any thoughts on this one? i have a kubota 22hp, which had been operating flawlessly for the last 6mths. suddenly its started the following traits- it will run great for about an hour at 2500rpm, engine pressure ok, temp ok, water out the exhaust ok, then for some reason, oil pressure drops, temp goes up, and the engine overheating alarm goes off. i shut the engine off for about 15minutes, then everything is fine again until the next occurence. any suggestions?
btw how do i put that radiator anti corrosion stuff in my engine? do i just add it directly to the radiator w/ some water?

sorry for asking what may be a dumb question. thank you


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## Freesail99 (Feb 13, 2006)

Do you know if you have a open system or a closed system ? I see you mention a radiator, but it sounds like your not sure if you have one.


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## TSOJOURNER (Dec 16, 1999)

mrkeith,... how old is the engine, when was the engine last serviced and what was done. Does this happen at a lower rpm when operated for the same length of time?

....radiator? anti-corrosion? .... are you asking about coolant in the fresh water tank? or about a cleaning agent to remove mineral build up in the heat exchanger?

Have you checked the basics to ensure that the amount of water flowing to the engine has not changed? i.e. clean strainer and through hull, the sea water hose is not restricting flow, impeller blade(s) in the system. Is the fresh water side filled with coolant/water, are you having to refill after running the engine for a while?

... George.


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## Denr (Feb 7, 2001)

one word:

Thermostat


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## mrkeith (Jan 25, 2006)

sorry i wasnt more specific. the engine has a radiator and a fresh water heat exchanger, so there is a closed fresh water system that runs through the engine and an open system that runs through the heat exchanger to cools the fresh water. the radiator has recently been topped up and the oil has recently been changed. i changed the impeller a while ago (3 weeks) and noticed that some of the blades were broken off. the specific engine is a kubota d950. thank you


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## mrkeith (Jan 25, 2006)

also, the engine was new in 98, and i don't think they ever used coolant other than fresh water in the radiator. there is a bottle of radiator anti corrosion liquid in the boat, i guess i m not sure if that is suppose to be put in the radiator or its suppose to only be used to flush the radiator. the over heating used to happen at the lower rpms after the engine had run for a couple hous, but after i changed the oil it seemed to be ok up until this most recent incident. again, we were monitoring the engine temp and oil pretty religiously and it was fine until all of a sudden it went hot and the alarm went off. thanks again for all the info/help


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## TSOJOURNER (Dec 16, 1999)

OK,... First, something caused the impeller to fail, overheat and loose some of the blades. What happened? Has it been corrected?

Second, did you account for all the blades that were missing? Is it possible that a blade is disturbing the flow rate of the s/w. Is the input side of the heat exchanger clean of debris from the impeller?

Third, go to NAPA and pick up a gallon of diesel engine coolant, some come premixed others you will need to mix with DISTILLED water. Replace the fresh water with the coolant. Make sure you bleed the engine's fresh water system at the highest level, run and monitor the level, top off if necessary.

... let us know.


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## camaraderie (May 22, 2002)

*"i changed the impeller a while ago (3 weeks) and noticed that some of the blades were broken off. "

*Mrkeith...did you find those broken off impeller blade pieces? My guess is they are lodged in your heat exchanger and restricting flow.


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## sailingdog (Mar 19, 2006)

My guess would be no... he didn't fish out all the broken impeller pieces...


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## hellosailor (Apr 11, 2006)

Add my vote to impeller pieces being stuck in there someplace and clogging the flow. If you can't see them, you can try hooking up a hose and backflushing the engine coolant passages to try driving them out. (If nothing comes out, also try removing the impeller to do this.)

This is the main reason impellers are "supposed" to be replaced every year as preventive maintenance, so blades that eventually do break off won't cause blockages.

The antifreeze for your engine isn't just there to stop it from freezing, there are also usually water pump lubricants and other compounds in it, so while folks may argue about what is best, running AF instead of water is pretty much always a better way to go.<G>

I'd be somewhat concerned about the oil pressure drop though. Oil actually cools the cylinder walls, and then transfers the heat to the rest of the block and the coolant system. Check your oil level and then try to confirm if the oil pressure gauge is bad (it can happen) or why you really have low oil pressure (often just a failed pressure regulator spring in the oil pump).

The only dumb question is the one that goes unasked!<G>


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## sailingdog (Mar 19, 2006)

Most antifreeze formulations have a fair amount of anti-corrosive additives in them as well. So, timely servicing of the cooling system can help prolong engine life as well.


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## mrkeith (Jan 25, 2006)

thanks for all the suggestions. i know how this weekend will be spent!
i ll let you know how i go. thanks again


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## pigslo (Nov 22, 2004)

I disagree on filling the block with 100% antifreeze. It removes heat slower than water (that is why it does not freeze). It probably does not matter in the colder climes but in Texas it does. I use a 50/50 mix.
pigslo


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## mrkeith (Jan 25, 2006)

does it have to be diesel antifreeze or can it be automotive antifreeze?


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## trantor12020 (Mar 11, 2006)

mrkeith said:


> does it have to be diesel antifreeze or can it be automotive antifreeze?


I don't know where you're at but me, I use automotive antifreeze, Caltex Longlife (Green) or Shell (Amber). More for antirust property than freeze.
Did you changed the luboil filter when you changed the oil ?


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## pigslo (Nov 22, 2004)

I am pretty sure that antifreeze is antifreeze. Ethylene glycol is the old stuff. I don't know what the environmentally freindly stuff is.
pigslo


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## mrkeith (Jan 25, 2006)

i m in a warm climate, it will never freeze here. yes i changed the filter along w/ the oil


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## sailingdog (Mar 19, 2006)

Even if you don't require the anti-freeze properties of anti-freeze, it still pays to use the good stuff and change it out regularly, since the other benefits of the use of a good antifreeze still apply—like the anti-corrosion additives, which do eventually stop working.


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## hellosailor (Apr 11, 2006)

pigslo-
"I disagree on filling the block with 100% antifreeze. " No you don't.<G> You are just misreading "antifreeze" to mean "pure undiluted antifreeze" (whatever that may be) as opposed to "antifreeze" meaning, as most of us do, coolant mixed as indicated on the label. Antifreeze is like coffee: You may order and drink a cup of coffee, but we both know you wouldn't touch it unless there was already water in it.<G>

SOME antifreeze is actually sold premixed, so using it "undiluted" and "pure" will give you a 50-50 mix. Most is sold "pure", but you'd have to be nuts not to follow the instructions and mix it 50-50 (which works pretty well) or as appropriate for the temperature range and use.

The old stuff--the ethylene glycol base--is still a lot of different products. Some are incompatible with aluminum engine parts. Most have silicon silicate ("waterglass") in them or other anti-leak chemicals, which form a thin coating in the coolant passages to prevnt corrosion and leaking, but inhibit cooling. The popular antileak products can be a bad idea--unless you're leaking. The old stuff is almost always tinted green/blue.

The new "orange" stuff is more complicated. It is supposed to last much longer (doesn't break down from engine heat) but there are reports it is dissolving engine hea gaskets and wreaking other mayhem in certain systems, folks might want to search on that topic. Halvoline (Texaco), GM, and others make it and still stand by it, and many new cars are shipped with it. While facts are hard to come by, one thing they tell you up front is NEVER to mix the old and new stuff, an engine should be flushed before using the new stuff and failure to do so, leaving old contaminants, may well be the only real problem.

Then of course there's the 'pink' stuff, that's intended for R/V and summer cabin water supply lines. Non-toxic, breaks down quickly in heat, not for engines at all unless you're pouring it in the raw water intake to winter flush *that*.


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## mrkeith (Jan 25, 2006)

*weekend assessment/fix*

thanks all for the input. after running thru the system, heres what a found

- sediment in the raw water filter
- broken bits of impeller in the heat exchanger
- very dirty radiator water
- no thermostat
- 4 foot mooring line and plastic on the prop

remedies

- cleaned the raw water filter
- removed impeller bits and flushed heat exchanger
- replaced water w/ antifreeze in radiator
- removed rope/plastic off prop

ran it for about 2 hrs this sunday and engine ran cooler than normal and oil pressure kept normal. note i was running only 1500 rpms tho. hopefully this will work for longer motoring days.

thanks again!!!


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## sailingdog (Mar 19, 2006)

LOL.... 

Hmm... reduced flow of raw cooling water, a partially blocked heat exchanger, no thermostat, and crap tangled around the prop shaft... and you're wondering why it was overheating...


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## mrkeith (Jan 25, 2006)

yeah... call me a dumbsh*t. anyway, live and learn. at least i know my engine a bit better now.


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## sailingdog (Mar 19, 2006)

Hey, I wasn't calling you any names... it's actually good that you have had this experience now...since it makes it far more likely that you'll be able to solve any future engine overheating problems in the future...

I'd only call you a dumbsh*t if you hadn't gotten the heat exchanger flushed and gotten the broken impeller blades out of it. Basically, in this one experience you saw pretty much everything than can cause overheating in an engine.... all at once... Any one of those things could have caused it... In fact, I'm not too sure if there was anything that could cause it that you missed experiencing this go round.


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## mrkeith (Jan 25, 2006)

no problem i know you werent calling me anything, infact, *i* was the one calling myself a dumbsh*t! 

like you said i would have never done it if i had not had to and if you guys didnt offer suggestions. i m extremely grateful!


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## sailingdog (Mar 19, 2006)

De nada... I would look into getting a Globe replacement impeller for your boat. They're designed to be able to handle running dry better than most. It is generally a good idea to have a spare impeller aboard in any case, and getting a Globe one might be worth the slightly higher price. Also, if you haven't gotten a replacement impeller cover, I would highly recommend getting one of the quick access design ones.


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## mrkeith (Jan 25, 2006)

funny you should mention that...i was just wondering where i should go to get a spare (s) impeller and cover. any suggestions. the old one is a johnson pump if that matters ...i m guessing these things must have standard replacement conversions...?


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## camaraderie (May 22, 2002)

mrkeith...speedseal is the quick release impeller cover you should consider and here's also a link to the globe impellers which I think Defender carries.
http://www.speedseal.com/speedseal.html
http://www.globerubberworks.com/nav.php?products_impeller


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## sailingdog (Mar 19, 2006)

I forget the name of the company that made the speed impeller cover, but if you look in the back of most of the sailing magazines, you'll see them advertised.


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## mrkeith (Jan 25, 2006)

ugh i m back
i had the engine 'fixed' for the overheating, and the guy took off the cylinder heads and resurfaced them and put on a new gasket. in addition, he put on a coolant overflow tank so i could always watch the coolant level and i would know if i needed water/antifreeze. well, ignorant me i trusted this and i thought it worked pretty flawlessly over the past couple weeks. however, today i ran the engine for about 40 minutes and the dreaded overheat light came on, the engine was around 2300 and the oil pressure was around 20. i quickly shut off the engine and looked at oil.... fine. i quickly looked at overflow tank ...fine. the engine however was noticably hot, i looked at raw water strainer....fine..... so i took off radiator cap w/ a towel around my hand. alot off hissing/etc, but when i took it off and started to add coolant, just to see if it needed any (the overflow tank indicated it didnt but i would check anyway) the engine took about 2.5 ltrs of antifreeze! so clearly (?) the overflow tank doesnt work? anyway, w/ the radiator filled up, we started the engine, and a bunch !!! of green antifreeze came out of the wet exhaust, probably for about the first 45 seconds, then it cleared up again. so my guess is that there is some clue here that the problem never got fixed, the overflow tank doesnt work, and the antifreeze coming out of the exhaust for the first 45 seconds indicates that there is some violation in my fresh water/raw water system? any helpful suggestions? thanks alot again


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## Lancerbye (May 27, 2007)

I have been following this thread with some interest. I am new to this forum but not to boat problems. The only place that the raw water and the FWC system come in close proxiemety is in the heat exchanger. You might want to pressure test the heat exchanger. You might have a leak in a tube.


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## sailingdog (Mar 19, 2006)

Sounds like there's a hole or leak in the heat exchanger. That's the only place that you'd likely get anti-freeze in to the raw water side of the system. If there is a leak there, the overflow tank won't do anything, since it isn't overflowing...it's just leaking out.


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## camaraderie (May 22, 2002)

Keith...did the mechanic remove your heat exchanger and look for those pieces of impeller blades? I believe you have a corrosion problem in your heat exchanger and given the anti-freeze in your exhaust it may need to be replaced as this is the likely place for exhaust water and antifreeze to meet. At the very least, the heat exchanger should be removed and pressure tested and reamed out. Is there a pencil zinc on the heat exchanger....and has it been changed out...what shape was the old one in?


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## mrkeith (Jan 25, 2006)

thanks all, i will take the heat exchanger out again this week and have it retested. the first time we took it out there was not a leak, but they didnt pressure test it. also there were bits of impeller there the first time that were removed, which i originally thought was the problem. i was thinking, the problem really only seems to be an issue when the rpms start to get higher...i m guessing thats logical as the more pressure in the system, the more water is being forced out by the leak?


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## mrkeith (Jan 25, 2006)

one other question, am i correct in believing that when we saw the coolant come out of the exhaust, that this was a pretty good clue? meaning coolant should never come out of the exhaust right? cheers


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## btrayfors (Aug 25, 2006)

Right...you should never see coolant coming out the exhaust. 

There are several other possibilities where fresh (circulating) water can be mixed with the raw cooling water which goes through your exhaust, but let's hope it's just the heat exchanger. These are easy to change and relatively inexpensive 

Bill


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## mrkeith (Jan 25, 2006)

thanks for that. i will keep you updated


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## [email protected] (Apr 13, 2006)

to make you feel good,I operate several boats , my Kubota has operated in all areas from georgian bay to florida since 1973 and is still going good, but remember when it changes its tune ,check it right away it is talking to you..


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