How hot is too hot?

OHLowell

Member
Good afternoon all.

I have a 1947 9N/2N and I think it may be getting too hot.

I have lowered the coolant level to the core and not the cap but when I turn off the tractor is sounds as if the coolant is boiling in the radiator. This usually subsides after a few seconds. Is this normal?

On the other hand... I can bush hog or plow/disc for hours and the above mentioned "boiling sound" is the only indication that I get that there is an issue. However, if I use my finish mower in tall grass for an while the tractor will overheat and blow steam, only after I shut off the tractor.

Any thoughts? Am I getting this old tractor too hot or am I alright?

Thanks!

Lowell in Ohio
 
After working any tractor hard, you should let it run a little faster than low idle for several minutes to let things cool down! You
need to circulate the coolant and let the fan cool the coolant. Real low idle doesn't do that well.
 
Have you ever drained & flushed the radiator & block? It's not all that hard to do & could prevent a minor issue from becoming a real problem.

If the radiator is not overfilled, check for low coolant, a loose fan belt, debris in the radiator fins or a stuck thermostat. A bad water pump will usually squeak or leak. (If you ever have a water pump start leaking or making noise, replace it immediately. A N water pump will come apart & launch the fan into the radiator.) And, unless you have a new/rebuilt water pump from a reputable source, it could have impeller erosion. The pump will turn, it won’t leak, but it isn’t circulating water.

In order to have a stuck thermostat, you need to have one installed. Squeeze the top hose; if it has a t-stat, you can feel it. Sometimes (rarely) the t-stat can migrate in the hose & get stuck closed. Or, in an attempt to keep that from happening, some owners will put a third clamp on the hose & tighten it too much resulting in a stuck t-stat. The OEM top hose came w/ a non-adjustable ban to keep the t-stat in place.

The fan belt should have 1/2" of flex at the mid-point; no more, no less.

Unless you have a pusher fan, blowing out the radiator from the engine side is always a good idea.

But, sometimes you just have to bite the bullet & flush out the block & radiator. To do that, remove the t-stat from the top hose. Then, remove the bottom hose from the radiator, stuff a rag in the bottom radiator hose connection, & stick your garden hose in the top of the radiator. Turn the water on (reverse flush) & the water will flow into the radiator, then the block & out of the disconnected lower hose. Let it run until the water is clear. Then, check the radiator flow. Stick the hose in the top of the radiator; the water should flow out of the bottom w/o backing up in the filler neck. It should flow at 19.5 gallons a minute. As a final flush, put a gallon of white vinegar & about 2 gallons of water in the radiator, run it to operating temp & then drain it again. Don’t forget to put the t-stat back in correctly!

Use 50/50 anti-freeze & distilled water as your coolant. The anti-freeze contains rust inhibitors, pump lubricant & raises the boiling point of the coolant.
75 Tips
 
Finish mower and tall grass is likely to be your problem and your over working the tractor since you can brush hog and not have a problem. A finish mower is a extra large lawn mower and made for short lawn type grass conditions NEVER tall grass.
 
OHLowell.

In answer to "How hot is too hot", my OHV rule of thumb has always been, if you can't hold your hand on the valve cover . . . "Huston, we've got a problem!" :D

I know, sorry, no valve cover. :)
 
I run mine pretty hard and in hot summer temps 90+ with no problems. My radiator fins are smashed shut for about the entire radius of the cooling fan, I can only suspect a failed water pump bearing did this some time ago. Its never given me any signs of running hot with proper level of clean 50% coolant mix, good cap and a 180 t-stat.

If you only hear bubbles for a couple seconds, it doesn't really sound like overheating. When you shut the engine off, the normal hot spots will temporarily get the coolant hotter in that area of the cooling system because its not circulating anymore. Unless I missed it mentioned earlier, check the thermostat for being in backward too, also pressure test the radiator cap, 4psi is not much but it does make a difference in boiling protection. Are you running anti-freeze mix, maybe around 50%?
 
Thanks all for the responses!

I'll get on flushing out the radiator and block and verifying the thermostat and radiator cap are up to snuff and I'll get back to everyone.

Thanks again for the help!
 
running it for a bit, then a swing by the shop to drop a meat thermometer in the neck takes the guesswork out of it.
While waiting for the thermometer, looking in to check circulation with the now should be open thermostat will also tell you some stuff.
 
You can only hold your hand on something hot to about 110 degrees and engines and components are nearer to 200 degrees! Using you
hand to test for something hot doesn't work in the case of tractors!
 
Good grief!

I was only giving a light hearted general answer to the subject line, "How Hot is too Hot". I wasn't providing "advice".

In all of my past experience with overhead valve engines, in every single instance where I couldn't leave my hand on the valve cover for more than a two seconds, there was an overheating problem that had to be immediately dealt with.

So all I was saying was that if someone pulled up and said he thought his engine was overheating, as a quick check I'd go by valve cover temperature BEFORE ALL SERIOUS DIAGNOSTICS.

It's like having torqued so many nuts and bolts that you get to know the difference between what constitutes snug and tight and what the fitting will bear.

All I said was that it was my general rule of thumb that I will continue to use if I suspected overheating. If your OHV was operating normally and you put your hand on the cover a few times, you'd have a measuring guide and could detect serious overheating by feel if it was happening.

But I've only rebuilt about 10 engines complete, and umpteen other valve jobs and "overhauls' so sorry I interrupted the thread with my trivia. I inflated the rebuild number the first time. :)

To each his own.
T
 

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