Generator Overheating -- Kubota V1505

[Melbo]

My generator overheated yesterday and shut itself off.  Good thing for it to do -- has done it before so I figured may be low coolant -- no -- the hoses to and from the radiator were actually cool so I figured bad thermostat -- opened it up and the thermostat was open.

What to do next??? --- I removed the radiator and flushed it out --- normal flow and put cleaner in to set over night and flushed again.

Put everything back together and it still wants to over heat --- thought about it for a spell and figured maybe the thermostat IS bad so I replace it --- still starts to run hot.

The fan the radiator hoses and everything else is the same set up for three years now --- haven't changed a thing --- ran the generator earlier this spring to top up the batteries after the winter and it ran fine.

I am out of ideas PLEASE give me yours  (keep them as cheap as possible I don't need a new genset)

Thanks

Melbo

[luvrbus]

Mel, those little water pumps are keyed on the shaft that is probably your problem

good luck

[Melbo]

I thought of that and took it off and it is fine --- the impeller was all there and seemed to be solid with the exterior flange --- so I put it back on --- but I did check on that and the kubota place didn't have one here in town.

Melbo

[luvrbus]

You checked for a air bubble in the system ?

good luck

[Ncbob]

Melbo, does your unit have a 'puller' fan or a 'pusher' fan. It makes a difference. The intake air inlet must be at least the same size as the outlet in either case. Otherwise you're cramming 9 lbs of air into a 5 lb. bag.

If you're picking up your inlet air off the highway (road heat) you might wish to take another look for a better source.

Bob

[JohnEd]

He said the rad hoses were cool.  Water isn't being pumped around.  There are only two things that can do that besides a block that is completely filled with rust to the brim.  One is the thermostat and the other is the water pump.  Besides those you can have a hose fail ad shed the inside cover and it can block the hose be it a fuel or brake or water hose.  Your back is to the wall.....pull the hoses and make sure they are ok inside and nothing is missing that might have been sucked/pushed into the engine.

Some systems need "burped" to get all the air out.  If the block is higher than the rad that will be the case.  Bubbles stop the water pump from functioning.

Try to run the engine without a thermostat.  Make sure the impellor is actually turning with the engine.  Fill the thing with water and put a rag wrapped air nozzle in the hose and see if you can push water thru the block.

Pull the rad hoses and see if you can push air thru the rad like it was an open tube.  have no idea what would plug up the entire rad but this seems a stumper so into the odd ball stuff.

My money is still on the thermostat....remove it.

Wish I were there.  This is interesting.  Sorry for your troubles, mate.


John

[Melbo]

Took my girlfriend out on a date and just got back in --- Clifford the bubble in the system could be there --- I will try to bleed it tomorrow morning --- there is a valve above the thermostat that should do that nicely.

Failing that working I think I will remove the thermostat and both hoses that go to the radiator and run water back from the thermostat outlet so it come out of the lower inlet --- I will put that hose into a bucket to see what comes out.

Over all the system seems very clean -- no debris or "misc stuff" in the coolant so this is a mystery.  I changed the coolant about 3 years ago when I changed the radiator brackets BUT as previously mentioned it has operated properly since then.

I will update tomorrow.

Thanks for all the thoughts.

Melbo

[Melbo]

Well it was as Clifford said an "air bubble"  but not your ordinary everyday air bubble --- this one would not be moved by normal functions that would bleed any other air bubble out  this was a "SUPER" air bubble.

I blew air and or water through every section of the cooling system and even took off the water pump again --- tried to get the system to do a normal purge and when it all failed I knew that it called for drastic measures.

I drained the system down and flushed it with clear water a section at a time and then blew it out with air.

I mixed up a fresh batch of antifreeze and reassembled the system leaving the hose that connects at the thermostat loose. I filled the radiator with new antifreeze and then I blew air into the hose connected to the top of the radiator. Refilled and blew until fresh antifreeze came out the outlet above the thermostat. Then I reconnected the hose and started it up and it operated normally again. So as to avoid this happening again I put a coolant recovery tank on the radiator to "HOPEFULLY" keep any air out of the system.

Just remember when you ask a question and Clifford answers don't be sidetracked by other ideas. Just pay attention and follow directions.

Melbo

[artvonne]

  But what made the bubble?? I had an MGB when I was a kid, it never had heat. I tried everything and eventually gave up. What was interesting, was every time I bled the heater I got air, and momentarily had heat. I sold the car and moved on, but having run into simular occurances with other cars, and finding every single one had a blown head gasket, my money is on a head gasket failure in that MG.

  Anyway, I would keep an eye on it. Glad its working.

[Melbo]

I'm thinking that when running a little coolant was lost -- the configuration is such that the top of the motor is about 2 or 3 inches higher than the radiator.  I have been parked for about 9 months and just ran the generator a couple of hours this spring.  Just sitting let the coolant settle to the bottom and when it air locked I couldn't get it out with a normal purge. At least that is what I am figuring. I installed a coolant recovery system to try and avoid this happening again. I will watch it closely but it has been very reliable and this is the first time topping up the coolant did not get me back up and running. Thanks for all the suggestions. Nice to have it back in service.

Melbo

[niles500]

Melbo - Do you have a surge "tank" on your Genny?

[Dave Siegel]

Melbo that sounds exactly like whats happening on my generator. Ours is a 10KW Onan with a Kuboto motor. I have not used it several months and when I tried to use it it over heated. I have tried all the things you did except the air blast. Let me ask you, when this "super" air bubble released itself did it make a noise so that you knew something was gone?

Dave

[Melbo]

Niles

I have a coolant recovery tank now --- I didn't before --- I would just top up the radiator when this happened --- It only happened twice that I can remember in seven or eight years. I'm guessing that is what you mean by a surge tank.

Dave

I might not have done that except that I had been messing around taking things apart and putting them together --- water pump off then on --- running the system without the thermostat in place --- adding JUST WATER to top up the system --- after hours of checking EVERYTHING I figured it must just be the air bubble I was asked about. I put the entire system back together and filled the radiator with a good mix of antifreeze. If your system is already together just remove the hose above the thermostat housing. I put a clear plastic vinyl tube on the outlet above the thermostat and ran it into a bucket. The first time I blew air into the hose that goes to the top of the radiator of course I used too much pressure and had antifreeze blow back into my face so I had to stop what I was doing and go clean myself up ( I can sometimes be a slow learner ).  Once I got the system down I just gently let air push the antifreeze for a couple of seconds then I would stop open the radiator and top it up ( remember I was fighting an air bubble and did not want MORE AIR into the system ) then push the antifreeze with a little more air ( also the thermostat was in place and I was just forcing the antifreeze past it ) I did this procedure maybe five or six times until I consistently got fresh antifreeze mixture out of the top above the thermostat. Once I was sure there was no air left in the motor I connected the hose topped up the recovery system and fired it up.

Sorry for the long post.

HTH

YMMV

Melbo

[luvrbus]

Mel, you won't have any more problems now a recovery tank is the way I solved my air lock problem  also Dick Wright and I had some good (heated) conversations about air locks on his generators Lol I think he ships a tank with his generators now 



good luck

[JohnEd]

I have this problem with my Lexus V8 SC400. (don't get excited...it's a 93).  My engine has a "purge" plug on the top of the engine.  My first symptom that I have a bubble is that the heater stops putting out any heat.  I think the engine might be running a little hotter but I don't get much of a deflection on the gauge.  If I remove the plug the chamber immediately under it is dry.  Filling it doesn't quite resolve the issue.  I need to fill the system, start the engine and crack the plug till I get coolant out and then I am good to go.  That's the "right way" to do it.  

This heat interruption has happened on the road, in the winter, and at night.  Chilly!  After a half hour of freezing my XXXs off I mashed the gas pedal at 60 mph.  The car will actually go into "low" and smack you in the back as it hits red line and shifts without the slightest hint of subtlety, into second.  YeeHaw, teenager time, again!   Then the wave of heat hit me in the face and all systems were go once again.  Seems you can "blow" the bubble out of the system....at least on my engine.  After that experience I got on the Lexus board and got the answers to my question.  Discovering the "burp" plug, I no longer need to gets ticked of at the car to get heat.   Aren't boards great?

My car does this a couple times a year and it only started a few years ago.  I might have a tiny head gasket leak.  Then again, all cooling systems "out-gas" something....all of them.  My engine and apparently the Kabota are sensitive to that circumstance.  Point being here is "try revving the hot engine with the thermostat wide open to move the bubble".  In the shop the loosening the purge plug or a "high-on-the-block" fitting/union would be more subtle.

HTH,


John