# Overheated - How to tell if engine is damaged



## zdanman

Wondering what the best telltale tests i need to run on a tractor (new kubota 200 hrs) that overheated.

It overheated because kubota doesnt have any protection for the coolant lines and DOES NOT have a temperature warning alarm (just a dumb light on the dash thats extremely hard to see in the sunlight) and a stick got wedged up between the axle and radiator punchering it. By the time i looked down and noticed the temp gauge it was in the red.

*What test should i run to see if i ruined my new tractor forever...? What telltale signs to look for that would tell me that the engine was hurt and will see problems prematurely in the future? Thanks for any info?*


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## Hoodoo Valley

Welcome to the forum zdanman! Depending on the length of time and the amount of coolant lost, it could have blown the head gasket to a varying degree, or set things up for it to blow later down the road. In the long term, it might now use oil.

When you went to add coolant, how much did it take verses what the capacity is? In other words, how much coolant did you loose? All of it, just a quart? It can still over heat and be fine........ because you caught it seconds after the light came on.

Also, I don't know what size Kubota you have, but on the smaller units such as my BX 2200, with hydrostat, they have a plastic fan just ahead of the rear end / hydro that is easily chewed up by brush and sticks.......


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## zdanman

Well heres the thing... I dont know HOW LONG it was in the red. I just know it was...
I cut it off immediately and saw it was leaking coolant under the radiator.

I rushed to go get a jug of water... but who knows how long it was between when it got to red and before i was able to dump water in it and crank the engine back up to cool it down.

I changed the oil and radiator. Did a compression test although I didnt know what I was really watching for.


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## Thomas

Have you try running tractor since than?..if so does the red light come on quick and here any strange noises or signs of fluid seeping out?

Have you clean the outside of radiator...air hose or water?
Some model offer radiator cap that will whistle if high temp should happen.


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## Fedup

So is this post mainly about what signs to look for concerning possible damage, or is it a rant about who's to blame for the current condition of the tractor?
On the first count. Once the coolant leak(s) were addressed, does the coolant level remain constant? Any signs of coolant loss, whether on the ground, out the exhaust or into the oil? Does the engine start as before, sound any different(whether cold or warm), does it smoke more than before(if so what color smoke)? Any increase in blowby or crankcase pressure? Any noticeable loss of power under load? Any increase in oil consumption? If nothing has changed in these areas you may well be all right.
On the second count. The terrain and obstacles you choose to drive through/over are not the fault of Kubota. Neither is your ability(or lack thereof) to keep an eye on the gauges. In addition --- pouring cold water into a hot engine is usually NOT a good plan to begin with. Probably better to just let it cool naturally even if it's low on coolant. If it's too hot to put your hand on it, it's probably too hot for cold water.


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## Hoodoo Valley

I was going to hit upon some of these things or elaborate further, but I figured he might need a buffered moment or two before getting the full realization. (smiling) The bummer here is that on older engines, they are more tolerant of these sorts of things than a newer engine still under warranty. I hope it all works out.


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## zdanman

"Any increase in blowby or crankcase pressure?" what do you mean by this? how to check this? i will post a video of the compression test when i get home.


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## zdanman

ok so i dont notice a dramatic change in sound...

so basically im looking for loss in oil and coolant only? any other things to look for that means the engine is prematurely worn.....?


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## Fedup

Over heating for short periods isn't always fatal. However, it can have ill effects that may take time to show up. In severe severe overheating, the piston/ring to cylinder wall clearances can be reduced to the point that scoring takes place which later affects piston skirt, ring, and cylinder wall surfaces to lose sealing effectiveness. This can allow more compression into the crankcase(blowby) and more oil from the crankcase into the combustion area (blue smoke and oil consumption). 
In addition, headgasket failures can occur allowing coolant into combustion chambers and/or into the crankcase. This may take a few hours or more of operation to show up to a degree they can be noticed. I'm not aware of any particular tests that will be of any great help at this point unless any symptoms appear. Also pay particular attention to how the engine starts, runs, sounds, and performs as compared to what you remember from before this incident.


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## FredM

At the worst, overheating can take the tension out of the piston rings and over time you will notice the engine starting to blow blue smoke, starting may or not become harder to get the engine running.

You could remove the radiator cap and with the radiator full, start the engine and run at idle until this reaches operating temperature, you will have to allow this so the thermostat opens and the water circulates, now watch for bubbles in the water in the neck of the radiator, if these are major bubbles, then you may have a distorted head or unserviceable head gasket.

Your biggest mistake was to pour cold water into a hot motor, you wasn't to know this of course, the effects of cold water in a hot motor is a disaster in that this will crack cast iron heads and at worst, distort aluminium heads, lets hope you don't have these problems and your tractor is ok.


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## zdanman

ok so the telltale sign of blowby is low compression during a compression test?

heres me doing the compression test. did it through the glow plug inlet. it was like this for all cylinders:






after it got to 550 it dropped slowly down to about 540 before i let out the pressure. let me know what you all think.

the telltale sign of oil getting past pistol rings is oil loss? (because its getting burnt in the cylinder)

the telltale sign of coolant getting into crankcase is milky white oil?

the telltale sign of coolant getting into cylinder is loss of coolant?

you said that cold water will crack a hot head. what sign will tell me if i have a cracked head? (im assuming mine is iron... i think my kubota is a 2011)

is it possible that overheating didnt hurt the engine at all or not possible at all and there definitely was damage regardless of severity?


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## sixbales

Howdy zdanman, welcome to the forum.

Your compression test pressure is fine, indicates to me that the engine is in good condition. Put your tractor back to work. My GUESS is that the overheating didn't hurt the engine at all.


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## FredM

sixbales has said what I would have said, run your tractor and work it, if the overheating had of been bad enough, the pistons would have grabbed, I wouldn't be worrying too much.


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## zdanman

thanks but im still curious....

you said that cold water will crack a hot head. what sign will tell me if i have a cracked head? (im assuming mine is iron... i think my kubota is a 2011)

is it possible that overheating didnt hurt the engine at all or not possible at all and there definitely was damage regardless of severity?


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## FredM

A cracked head will show in a couple of ways, --- a crack in the combustion chamber allowing water to enter and this then will cause misfiring if the crack is bad enough, and combustion pressure will show as bubbles in the coolant --- and as I mentioned previously, remove the radiator cap and watch for bubbles breaking in the coolant water,--- bubbles will also show in the coolant if the head gasket has become unserviceable

A crack in the oil passages will allow water to enter the engine oil and this will show up as being milky.

I inverdantly overheated my Kubota through a failed thermostat while mowing, the radiator overflow was making like a steam exhaust when I noticed this, that was at the beginning of this year and so far there has been no problems, I do have very small bubbles in the radiator water, but these were there well before my overheat, and the engine oil is not contaminated.

Use your tractor and watch for signs if you are worried, milky engine oil and lots of bubbles in the radiator water, I would imagine you would check engine oil before each daily use, radiator water has to be heated to check, do this occasionally with the cap removed and allow to warm up, the coolant has to be circulating through the engine.


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## zdanman

will do. 

do you ever worry that when you overheated it burnt the rings or something that will show up a year or two later instead of immediately?


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## FredM

I was more worried about the head getting a crack in it, the older Kubotas were prone to head cracks from overheating, and were known for this, I am not worried if some tension has gone from the rings, a little blue smoke doesn't hurt anything and shows that the lube is working around the pistons, the B2400 starts and runs ok for its age, around 95 vintage.

If you are really worried about the engine, your only option then is for you or the dealer to remove the head and inspect the head surface, and block surface for square and each individual bore for scoring, and matey, that will cost a lot of money if this is not needed to be done.

If your engine is not making any different sounds since the overheat, stop worrying.


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## Hoodoo Valley

zdanman said:


> Do you ever worry that when you overheated it burnt the rings or something that will show up a year or two later instead of immediately?


You mean as in after the warranty is up?

I second what everyone else has said, that you'll be fine.


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