Radiator Drain - Spontaneous Leak?

What would make the radiator drain in a TO-20 spontaneously leak, and drain about a quart of coolant?

Background:

1. Last weekend, I drained the old coolant, and flushed the system, using water only, as the old coolant was pretty clean. (I only changed it because I recently bought the tractor, and didn't know when it had been changed last.)

2. I also installed a thermostat - some Previous Owner had removed it.

3. Again, last weekend, put in new coolant/water mix, everything looked fine, no leaks, 'stat seemed to be operating.

4. Yesterday, I installed a new temperature gauge, as the old one wasn't working. (It looked like the cap tube was buggered up.)

NOTE: I didn't open the radiator drain to lower the coolant level - I used the block drain.

5. Ran tractor to confirm new gauge was working. (It was.)

6. An hour later, found about a quart of coolant on the garage floor, that looked to be coming from the radiator drain. It was still dripping, and did so whether drain was open or closed.

7. Replaced lower drain (that was fun) replaced coolant.

8. I haven't run the tractor again yet, because I didn't have time last night.

Please note: the radiator drain hadn't been opened since last weekend, and hadn't leaked until yesterday.

Any ideas? Thermostat stuck? Bad Cap? Or just a bad drain valve, and a coincidence?
 
It may have boiled over after shutdown. If you fill it more than just above the core it will boil over. I'd run it for 20 minutes and see if it boils over again. It'll find the correct level by over flowing. If it continues to over flow after falling below the top of the core, I'd start looking for other problems, ie. tstat in backwards, blocked radiator/passages...etc. As long as the hoses don't collapse, has good flow and it levels out it should be good to go.
HTH
DON TX
 
Checque the drain valve to see if it in fact is closed. IIRC screw IN for off and out for on. Most likely what happened is that when u drained and flushed th system it dislodged stop leak or rust that was plugging it and keeping it from leaking should the valve be bad.

BTW, draining and flushing and replacing coolant is absolutely uneccesary unless some cooling problems develope that have caused the antifreeze to be contaminated. Example such as flood vehicles. PERMANAnT Antifreeze does not loose its freeze protection, EVER. Will loose some water pump lubricant capacity but that is minimal to begin with.

IF the cooling system is not causeing problems then LEAVE it alone!!!!

THe draining and flushing and replacing of antifreeze is strictly an industry gimmick. I have vehicles here i've owned in every day operation for as long as 12 to 30 years, 60K to 190K miles and NEVER changed the coolant.
 
Did you fit the Thermostat the correct way around, that is with the "bellows" to-wards the Engine, if it was fitted the opposite way the engine could overheat as the Thermostat would not be in the hot water from the engine which would cause it not to open. You got it hot enough as you confirmed when you said the gauge was working OK, so it is possible that it did get too hot and this is what caused the problem.The fact that water was dripping from the tap, that could be that the water was dripping out of the radiator itself when you filled it or there is a leak, it would look as though it was coming from the tap as that is the lowest point. There is also the possibility that the leak is why the original owner removed the Thermostat to keep it cooler or to stop it pressurising the system and blowing all the water out like you have now. It could be the Head Gasket that is also the cause of your problems or even a Cracked Head. If you need more help, email me at the address below and I will send it to you, just tell me what you have done...John(UK)[email protected]
 
i always keep my radiator cap loose, takes the pressue off the cooling system, you do not want to blow up that old radiator.

santa might not bring you another one, unless you have been a very good boy.

works fine on my old to-35 for years and old rotten radiator still works fine.
 
Thanks to all for the replies.

Well, except for John (UK), for raising the possibility of a blown head gasket/cracked head! :cry: (Just kidding, John - if that's a possibility, I guess I need to know it now. I really haven't noticed any other symptoms, and the radiator coolant and crankcase oil are both clean.)

I'm sure the thermostat is pointed in the right direction, and that it was operating properly immediately after I installed it, as I could see the water flowing in the radiator.

I'll check it in a pan of hot water this weekend, to ensure that it's still opening.

I also considered the idea that the leak was coming from the radiator itself, and not the valve - I'll try to check that more closely, too.

Finally, I'll take the cap to my local auto parts store to have it tested, and to make sure it's the proper 4 psi cap.

FYI: the radiator has a tag on it, indicating that it paid a visit to Midwest Radiator in Kansas City, which has been the "go to" radiator repair shop in this area for a LONG time. (The tag has been on the radiator a LONG time, too.)

Thanks again. As the new owner of an old tractor, I continue to be amazed at the helpful folks who frequent this board.
 
Update:

1. Thermostat was installed in the right direction.

2. Checked thermostat in a pan of hot water - it opened at the right temperature. (Pretty close, anyway - maybe a little high.)

3. Started tractor - no leaks.

4. Ran for a half-hour or so, grading my driveway, with no problems.

5. Checked radiator, and thermostat looked to be open - water moving nicely in radiator.

6. Parked, let cool - still no leaks.

It must have just been the radiator drain.

Only problem: the newly-installed temperature gauge doesn't register correctly - needle just barely rises off the lower peg (130 degrees F.), but from what I've read in the archives, that's a common problem. (Yes, the gauge works - I checked it by putting the probe in a jar of boiling water.)
 

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