Coolant overflow normal?

Sat Jun 22, 2013 10:53 pm

I finally got my Woods mower attached. Happy to be getting some seat time and admiring how well the cub and mower were working together when after about 15 minutes of cutting I noticed coolant coming from the overflow tube at the base of the radiator. Thinking it was getting ready to overheat I shut it down. The coolant level was just below the base of the filler neck like it says in the manual and the radiator fins aren't clogged with anything. Was it likely to overheat? Or is this possibly just normal expansion?

Thanks, Dan

Re: Coolant overflow normal?

Sat Jun 22, 2013 11:14 pm

Dan, If you had just topped off the radiator it is normal for the coolant to escape, The coolant level will drop to a point then stop. As long as I can see coolant in the radiator I don't worry about it. I have never had one of mine overheat yet and I live in Fla

Re: Coolant overflow normal?

Sun Jun 23, 2013 7:41 am


If you fill it to just below the top of the filler neck (just below the over flow tube) there will be coolant escaping as the Cub warms up to operating temperature. A thermo siphon system does exactly that, the coolant will heat up and over flow until it has reached it's proper level where it will then usually stay. All you need to do is check occasionally to make sure that there is coolant and it is just about even with the top of the rad.

Re: Coolant overflow normal?

Sun Jun 23, 2013 8:01 am

Mowing is tough duty and if your cooling system is marginal, you will overheat. Even if you have the coolant at the recommended level, it will expand enough to overflow and even outright belch. If you are talking a couple of drops-no big deal. If you are talking "I can see the fins after cool down and it needs a quart to cover them" then you need some attention. You should make sure your timing is right as this can impact operating temperature. I doubt that this is an issue but it is always good to check the basics first.
What is more likely is that it is time for a block flush. Download a copy of this cooling system manual and get up inside the block and flush the crud out that is causing hot spots. If you have a pressure washer, that works great! It agitates everything and the crud come pouring out. Others have used a flushing tool wand attached to a garden hose. After the block is clean and topped up with new coolant, make sure you add a bottle of rust inhibitor every year and you will extend the life of your flushing efforts. Coolant does not go bad, but the inhibitors are consumed with time.

Re: Coolant overflow normal?

Sun Jun 23, 2013 8:18 am

Thanks everybody for your responses. I was probably overly cautious. Didn't want it overheating and causing other problems. I'll double check the timing and consider a block flush too.
By the way, If it were overheating what would one likely see, steam from the top of radiator as with a pressurized automotive system?

Re: Coolant overflow normal?

Sun Jun 23, 2013 8:27 am

If you were seeing steam, then some boiling was going on. The hot spots near the top of the cylinder cause localized boiling which has many more times the volume of liquid. This is what causes major belches. You should not be seeing steam coming from a cooling system in good order. Again, mowing works an engine hard. Combine hours of mowing and a hot day and a little expansion out the overflow is to be expected. As long as you can still see coolant covering the fins when it has completely cooled down, you will be fine.