Super A running hot

I have a 1949 Super A with a C123 engine installed with no water pump(as original C116 did not use one). Radiator is clean, I had it checked for flow at a radiator shop, checked good, engine runs hot regardless of load. Engine is in good condition, good oil pressure, no oil use, starts and runs great, good air flow thru radiator. My question is do I have to install a water pump??? Won't the C123 work with the Thermosiphon cooling system??? that the C116 used. Any Ideas??? Thanks.

Is it losing water? If you fill if level full or close even it will lose water.
Put a thermometer in the top and check the temp. Thermosyphon will naturally run at 180 degrees.
What kind of load are you putting on the tractor?

You need a water pump with a C123. It is my understanding that the water passages are smaller, thus thermosiphon does not word properly. I can be corrected.

likly the cause of you'r overheating is the deposit of rust and sludge at the rear of the block if you' tractor was never equiped with a water pump , if you remove the radiator and lower water outlet you can reach inside the block with along screwdriver and scrape the rear of the water jacket then use a long blower gun with compressed air and force the loose rust out the outlet and keep doing it untill it looks clean. carefull not to knock out the freeze plug at the rear of the block or you will have to remove the engine to reinstall it.

It might depend on what manner of 123 you have. If it was built as a 123, meaning it came out a late C, a SuperC or a Super A-1, then CNKS's point about narrower passages may be in play.

If it started life as a 113 and is now a 123 by virtue of having been overhauled and having the original 3" sleeves replaced with 3-1/8", I shouldn't think the passages are your problem.

Built up sludge at the rear of the block and head as has been mentioned is a common find. In overhauling both my tractors' motors (113 on a BN thermosiphon and 123 on a SuperC with pump), both motors had a wedge of sludge that sloped down from the top of the rear of the water jacket to bury/surround about half the sleeve on #4 and about a third of #3. Similar though not as pronounced in the head.

An easy and not to messy way to estimate whether that's the problem is to start with your coolant at the regular operating level, then drain it into gallon jugs. The system holds 13 qts. If you get too much less than that, and certainly if you get less than three gallons, then it's fair to assume you've got a lot of sludge in there (13 qts minus the quantity drained = the volume of the sludge) causing your overheating. If that's the case a cleaning like el61 described is in order. That's easier to do well if you remove the fan, and then the radiator leaving the hoses right on and unbolting the lower inlet from the block and the outlet from the head so you can see and get air and water in there to clean it out. Air works but so does some scraping with a coathanger or whatever else you can get in there, as well as a high pressure stream of water, even if it's from a garden hose nozzle.

If the block and head are clean, you might have a look at your ignition timing. If it's too far retarded, the gas will still be burning when the exhaust valves pop open and cause you to overheat. On a magneto, that could be caused by your impulse sticking, meaning the motor is firing at TDC instead of 35 degrees before. On a regular battery ignition distibutor, it could simply be misadjusted, or it could be your advance mechanism isn't working properly (a few various causes for that).

I'd check out the sludge situation first. See how much coolant you get out of it and go from there.

Thanks for the reply, It is a C123 block, I can hear the mag impulse clicking when I turn it over with the hand crank, it starts so easy that the timing has to be close, but I have not checked it,I will check out the sludge problem. I bought the tractor from an estate and it has been sitting for years, it appears that the engine was installed some time ago and was worked, so I don't know if the heating problem is new.

Thanks for the reply, I will check out the block for sludge.

Thanks for the reply, I had this same thought, but I could not find anyone that had a similar experience, the local IH dealer didn't know for sure if it required a water pump. This engine appears to have been installed years ago and worked, I don't know if the over heating is an old problem.

Thanks for the reply, It does push a little water out of the over flow until it seeks it's own level, but doesn't get hot enough to boil over. The only load is a 42" Woods belly mower.

If it's not boiling the water out and dropping the level, how do you know it's overheating?

Thanks for the reply. Upon further inspection I found that the over flow tube had been crimped shut in side the fan shroud, not in plain view??? (old auction trick???) after fixing this the rad does lose water when it gets hot. I picked up all the parts to install the water pump today as I think it is sure to solve my problem.

Scotty: I like your suggestion to drain the system and measure to amount of coolent to determine how much sludge is built up inside. Simple... why didn't I think of that.. The rest of your post was good too. ag ret.