International Cub - Radiator Overheating and Overflowing

Hello Gentlemen,

First I must admit that I am complete novice when it comes to engines and tractors. I have inherited an International Cub from my father. It is a mid '70s model...the yellow and white variety. It has served my father so well for so many years but the last couple of years it has started to overheat and the fluid/water overflows after about 5-10 minutes of use even if it just sets there.

I have had the radiator rebuilt, the carburator rebuilt and the head gaskets replaced when the head was taken off, it had warped a little but was able to fixed.

It doesn't burn oil. But I have noticed that for a long time that it doesn't have the power it use to.

Primarily I'm concerned about the overflowing fluid and the heat. I really have no idea what to do.

Is there anyone here that might offer a suggestion or some help. I'm willing to answer questions and take pictures if needed.

Thank you for your help in advance.
 
Is the engine actually overheating when the coolant is beginning to overflow? (Does it have a temp gauge, or use a cooking thermometer or infra-red thermometer?

Late ignition timing can cause overheating.

If NOT, you may have a failed head gasket or cracked head.

There"s all sorts of info and on-line manuals over at RudisCubs.com.
 
define overheating-

If you fill the radiator too high - it"ll push out what it doesn"t want as the water warms and expands.

It can spit out a significant amount and give the appearance of "overheating".

Do you have steam shooting out? or is it more just "boiling over"?
 
I admit that I fill the radiator all the way to the top but after 10-15 minutes (and then letting it cool a bit) when I go to refill it I am putting in about half the amount of the radiator to make up for what has been evacuated.

There is no steam just boiling over.
 
The head isn't cracked but it was warped. The head gasket has been replaced

I cannot speak to the actual temperature of the engine. That is a good question. I do feel that after using it for a short time that you can hear this sizzle in the engine which makes me believe that the engine is also very hot. I didn't notice that in years past.
 
well that's definitely a problem - wanted to be sure you weren't just seeing a little overflow from expansion.

If it were me - I'd clear out the radiator - blast it with a hose from behind.

pull the radiator hoses and blast the block out with a garden hose, see what kind of nastiness comes out - check the thermostat.

Been a while since I've touched one of those "newer" cubs - so can't remember too many details of them.

I assume it's got a water pump - be sure the belt's good.
 
You can't fill a Cub radiator right to the top.

The water expands and pushes out as the tractor warms up. It takes approximately 10-15 minutes before this happens.

If you keep filling it right to the top, it will keep pushing water out in a never-ending cycle. It is NOT overheating!

The proper fill level for a Cub radiator is just enough to cover the fins. You will have to shine a light into the radiator neck and look in at an angle to see the proper coolant level.

Cubs do not have a water pump or thermostat. They use a "thermosiphon" system where the water circulates by convection; hot water rises, cold water sinks.

Your power issue may just be a bad memory. The engine is probably down on compression, though, due to sitting so long, and running it will get it loosened up again. Ignition probably needs refreshing too. Valves might stand an adjustment.
 
I would pop the radiator off. Yes, I know there are lots of bolts to remove. I'm betting there is a lot of crap in the cast iron below it. Take off all your hoses to the engine and clean it good. Spray out the inside of the radiator and the engine block. You can use a pressure washer but be careful with the fins on the radiator. Replace the gaskets when you are done. When I rebuilt my cub there was about 4 inches of gunk in the bolster that the radiator bolts too...
 
Thanks for the information on how much to fill up the radiator. Again, I admit that I am a novice and may just be overreacting because of just how much water/fluid gets flushed out (at least half of what should be in the radiator). I worry that it is getting too hot.

The power issue though is real. We use to use the tractor for everything! It was the family workhorse. Now there is no way to even plow the garden. As soon, as the blades get into the ground it stalls out and dies. Using the mower bed underneath was great because you just increased the fuel and you could cut just about any heighth grass with ease. Now it bogs down and can barely make it through what it use to cut with ease.

How do I test/fix the compression?

I've had the had redone with new gaskets all around.

I agree that it sets for a long time between uses.
 
"How do I test/fix the compression?"

Remove all plugs and coil wire.
Open throttle all the way.
Screw in the compression tester in first cylinder.
Crank over engine 3 to 4 times and write down results.
Proceed to next cylinder and repeat.
There should be no more than 10% variance between each cylinder.

Now, squirt approx. 1 tablespoon of oil in each cylinder and repeat test.
If compression increases, it indicates a problem with rings; if no difference, it's a problem with valves.

I would think it would have to be a lot of variance in order to have a big power loss, though.
 
You need to run a cooling system pressure test. Your tractor shows all the symptoms of a blown head gasket. Yes, I know the head gasket has been replaced and I presume the warped head was milled. That doesn't mean it's OK now.

The typical way to check for a blown head gasket is to attach a pressure tester to the radiator and fire up the engine. If the pressure immediately skyrockets, you have a blown gasket or possibly a cracked head. (Turn off the engine quickly so you don't build up more pressure than the cooling system can handle.)
 

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