Kubota Radiator Cap Danger...

[Al Barrs]

If you have an older Kubota tractor check the radiator cap. If the rubber gasket is worn or frayed REPLACE it!

I own several Kubotas but on my G1800-S garden tractor w/mower attachment this morning the soldered radiator coolant filler soldered to the top of the radiator blew off and scalded both legs and my left arm. Upon investigating what went wrong and why the pressurized water didn't flow into the over-flow tank and then to the ground as it should and had before on occasion. Instead and apparently the radiator filler fitting soldered to the top of the radiator blew off and the expelled water scalded my legs and arm. Upon investigating why the overflow hot water didn't exited to ground I discovered all water lines were open. First I thought a dirt-dobber might have built a nest in the exit water tube but both exit tubes were open. I then discovered that the radiator cap's rubber gasket was frayed and had no doubt stuck and prevented the water pressure from activating the relief valve in the radiator cap which prevented the hot water from exiting into the overflow tank and then to the ground. I urge all, whether Kubota owners or other tractor owners to check your radiator cap and make sure it is in perfect operating condition... Don't let a few dollars stand in your way of avoiding great pain and suffering... Good Luck! I hope this helps and prevents further accidents...

 

[stevewarner1957]

Thanks for the post Al, I will check mine in the AM.

 

[diesel85]

I replace all my radiator caps at 10 years. Cars, trucks, motorcycles, tractors, etc... they are cheap!

 

[ganeydn]

This happened to my B8200 this morning. There was steam coming from the overflow tube, whistling, on and off as I was doing heavy work, and then all of a sudden, steam was coming out from under the hood in large clouds. When the air cleared and I opened the hood, a silver ring of solder was showing where the filler neck was supposed to be.

What can I do to get this fixed short of a new radiator?

Thanks

If you have an older Kubota tractor check the radiator cap. If the rubber gasket is worn or frayed REPLACE it!

I own several Kubotas but on my G1800-S garden tractor w/mower attachment this morning the soldered radiator coolant filler soldered to the top of the radiator blew off and scalded both legs and my left arm. Upon investigating what went wrong and why the pressurized water didn't flow into the over-flow tank and then to the ground as it should and had before on occasion. Instead and apparently the radiator filler fitting soldered to the top of the radiator blew off and the expelled water scalded my legs and arm. Upon investigating why the overflow hot water didn't exited to ground I discovered all water lines were open. First I thought a dirt-dobber might have built a nest in the exit water tube but both exit tubes were open. I then discovered that the radiator cap's rubber gasket was frayed and had no doubt stuck and prevented the water pressure from activating the relief valve in the radiator cap which prevented the hot water from exiting into the overflow tank and then to the ground. I urge all, whether Kubota owners or other tractor owners to check your radiator cap and make sure it is in perfect operating condition... Don't let a few dollars stand in your way of avoiding great pain and suffering... Good Luck! I hope this helps and prevents further accidents...

 

[Jim Nelson]

Most radiator shops can replace the neck pretty easily.

 

[Oldpath05]

Sounds like one of things that no one ever heard of..... I thought a radiator builds up a little pressure then stays there unless there's a severe engine problem. I'm not even sure why a radiator builds up pressure in the first place.

I only changed my coolant once in 12 years on my tractor when it became 4 years old, then 3 years ago it was down a little and only noticed that because of the temp gauge, maybe it's time to do a radiator check, something that I dont think is hardly mention on this forum.

 

[mrmikey]

I'm not even sure why a radiator builds up pressure in the first place.

If you mean what causes it, it's the water getting hot and expanding as well as creating steam.
If you mean what is the purpose, water under pressure boils at a higher temperature than water at atmospheric pressure. Ever wonder why coffee in an airplane is never as hot as what you make at home, lower pressure in an airplane therefore water boils at a lower pressure i.e....colder coffee......Mike

 

[ganeydn]

Most radiator shops can replace the neck pretty easily.

Thanks, Jim. Now: how to get the radiator out without spilling antifreeze on the field I was tilling.

 

[4570Man]

If you mean what causes it, it's the water getting hot and expanding as well as creating steam.
If you mean what is the purpose, water under pressure boils at a higher temperature than water at atmospheric pressure. Ever wonder why coffee in an airplane is never as hot as what you make at home, lower pressure in an airplane therefore water boils at a lower pressure i.e....colder coffee......Mike

Who heats coffee to the boiling point? And shouldn’t the radiator not be hot enough to boil either?

 

[repete]

If you mean what causes it, it's the water getting hot and expanding as well as creating steam.
If you mean what is the purpose, water under pressure boils at a higher temperature than water at atmospheric pressure. Ever wonder why coffee in an airplane is never as hot as what you make at home, lower pressure in an airplane therefore water boils at a lower pressure i.e....colder coffee......Mike

Good response Mike. It is important to develop this pressure as it, in combination with the proper coolant does raise the boiling temperature. This causes the coolant, as it contacts the cylinder head, to stay in contact as opposed to "vaporizing" as it hits the higher temperature at this location and consequently a better heat transfer occurs.

 

[ganeydn]

I must say I was surprised that the pressure built up enough to blow the filler neck, since steam was escaping through the overflow. When the whistle blew, I took the load off the tiller and let the engine run to cool it down. That worked several times until it didn't. Could the overflow tube have gotten clogged?

 

[repete]

I must say I was surprised that the pressure built up enough to blow the filler neck, since steam was escaping through the overflow. When the whistle blew, I took the load off the tiller and let the engine run to cool it down. That worked several times until it didn't. Could the overflow tube have gotten clogged?

I think it is a case of PSI times square inches = pounds of force. The cap outlet, being smaller in diameter than the top of the filler neck, means that the filler neck in actuality may have more "force" against it than the cap itself. Over time this pressure, no pressure, pressure will take a toll on a solder joint, especially if there is any corrosion attacking the solder joint.

 

[ruffdog]

If the filler neck was forced off, the solder would have a dull torn look. If the temperature was hot enough to melt the solder, it would be shiny. I remember reading about kubota radiators with plastic tanks melting right where the upper hose meets it. Why is the coolant getting that hot?

 

[mrmikey]

Who heats coffee to the boiling point?

I don't heat coffee to the boiling point but I like hot coffee and I heat the water to that point. I always nuke take out coffee......M

 

[ganeydn]

If the filler neck was forced off, the solder would have a dull torn look. If the temperature was hot enough to melt the solder, it would be shiny. I remember reading about kubota radiators with plastic tanks melting right where the upper hose meets it.

It was shiny.

Why is the coolant getting that hot?

My question, too.

 

[JWR]

If the filler neck was forced off, the solder would have a dull torn look. If the temperature was hot enough to melt the solder, it would be shiny. I remember reading about kubota radiators with plastic tanks melting right where the upper hose meets it. Why is the coolant getting that hot?

Water in a radiator cannot get hot enough to melt solder. You will not ever see that. If the radiator was plastic then some crack around the neck below the radiator cap developed and finally blew. If it was metal then it was a very RARE blow off of a neck on a radiator. Many things had to conspire and be wrong at the same time. The cap shold have released the pressure LONG before the neck was damaged. Hoses should have blown before the neck was damaged. etc etc. This is an odd one at best. Probably more to the story of course & no way to know ...

 

[ganeydn]

Water in a radiator cannot get hot enough to melt solder. You will not ever see that. If the radiator was plastic then some crack around the neck below the radiator cap developed and finally blew. If it was metal then it was a very RARE blow off of a neck on a radiator. Many things had to conspire and be wrong at the same time. The cap shold have released the pressure LONG before the neck was damaged. Hoses should have blown before the neck was damaged. etc etc. This is an odd one at best. Probably more to the story of course & no way to know ...

Several things to report:

1. The mechanic who works on my car told me how to drain the radiator - drain plug at the bottom. (Of course, the drain plug fell into the jar, but it won't be to hard to get it out.)

2. He told me about 4 bolts to remove the radiator - turns out there are only two needed to remove it, but of course, all the shrouding needed to be removed first, as well as the hoses, one of which had to be cut.

3. Successfully removed the radiator.

4. He told me about a nearby radiator repair shop where I'll take it within the next couple of days.

5. Although the place where the filler neck came off the radiator was shiny yesterday, today it's dull. Must have oxidized overnight. It's been rainy.

6. JWR, I agree that it's very strange that it got hot enough to melt the solder. There must have still been water in the radiator when it blew because there was a huge cloud of steam when it did blow. Could be that the radiator cap didn't release pressure properly, but just before it blew, the pressure relief tube was whistling, releasing steam. So perhaps the connection between the neck and radiator was weak. I don't remember how long ago the radiator was replaced, but i'm sure it was less than 10 years. Perhaps the radiator repair guy will have some ideas.

Thank you everyone for your thoughts and comments.

 

[Gator6x4]

You have a serious problem. It sounds like you have a blow head gasket that caused the water to heat to boiling and the engine exhaust gases and the boiling water pressurized the radiator to the point of blowing the filler neck out. A very dangerous situation.

Watch this and see what you were probably feet away from.


Electric Water Heater Explosion in Phoenix Arizona and rocketed through the roof of house. - YouTube

 

[ruffdog]

I'm thinking the engine went way above normal temps because of flawed thermostat/head gasket/pump problem, then, as overflow was whistling away coolant violently blasted at high temp steam. Yes, I would be looking at all things for causes.

 

[JWR]

All water heaters come standard with a pressure relief valve besides being required by code. Wonder why that did not work int he You Tube Phoenix AZ case ?