Rad boiled over!

Sun Feb 01, 2004 11:21 pm

Hmmmmm..............Here's what happened:

Finally put my carb back together and installed it on Frank, my '67 Loboy.
Fired right up and sounded great. Took it out for a spin, about 1/4 mile and back to the shop. Just as I got there the rad started to boil over, shut it down and pushed it into the shop. I'm about to rebuild and paint this one so I set about to find out why it boiled over. Before draining the rad, I felt the lower pipe to the engine block, it was cold. There was anti-freeze in it, and the shop has been warm for 3 days so it was not froze. I started to remove the drain plug and was getting ready for hot water, but no, the water coming out was cold, very cold, then started to get hot as it drained out. It was almost all out when I felt the lower pipe again, this time it was very hot. It's almost like there was a blockage, and half the water was cold and half was hot. I removed the rad, the head, the lower pipe, and the short pipe to the steering bolster, NO blockage anywhere, and suprisingly clean. The head gasket shows some sign of blowby, and possibly getting into the water jacket but not sure. Any idea why it would boil over with no blockage? The cylinder walls are not scored, but will need to be de-glazed. The rad itself is not plugged either, as I plugged the top pipe and over flow and was able to blow through the rad with no effort at all. I'm stumped.

Sun Feb 01, 2004 11:30 pm

Ez, You've been around cubs long enough to know you can't keep a cub radiator full to the top, so I won't tell you not to worry. Blowing through a radiator won't ell you if it is plugged. It takes a lot more area for water to flow through than just for air. You may have some tubes blocked, or there may be trash in the radiator blocking the airflow. I would suggest taking your radiator to a radiator shop to be boiled out.

Sun Feb 01, 2004 11:34 pm


Just to rule one possibility out... Did you recently add the coolant, and if so, did you pre-mix it?

Mon Feb 02, 2004 12:44 am

You are right, I have been around these cubbies long enough. Thing is, the rad was not filled to the top. In fact the level was the same as in my '49 and no problems with that one. The rad is in pretty bad shape as there is evidence of an earlier "rad/fan incident/ mishap" no leaks though.

Geo, I will be honest and say, no I did not premix. I poured in a good batch of anti-freeze and then filled the rest with water. This was a few months back after flushing the rad with "rad flush". I was not planning to work it but only filled the rad as it was going to sit awhile before I had time to rebuild the carb I was going to use.

I'm thinking of replacing the rad anyway. Lot's of work ahead swapping out timing cover ( fan "ears" were broke and poorly repaired ) etc....

I'll be picking the brains of you gurus for awhile, and hopefully gain some more knowledge on the way.

Mon Feb 02, 2004 10:09 am


I think you have your answer! The anti-freeze and water (because of their different densities) didn't mix, and your blockage was "hard" water.

Mon Feb 02, 2004 11:42 am

EZ i save an empty gallon antifreeze jug so that i can premix 50/50 and end up with 2 gallons of ready to go -40 antifreeze. mark the jugs with a magic marker. otherwise, my fergetter get's me confused.

Tue Feb 03, 2004 1:42 pm


You may have a point there.
At this point it don't matter much as I'm strippin' er down.
Looking for an engine stand right now.


Keep on Cubbin'

Tue Feb 03, 2004 6:28 pm

EZ, check out Princess Auto for an engine stand. They have em starting from about $50 and working up.

Tue Feb 03, 2004 7:21 pm

:lol: Untill I reacently saw A soft water comercial, I always thought hard water was Ice Cubes"" Hee Hea, That was Good George"" :shock: :lol:

Tue Feb 03, 2004 8:40 pm

EZ wrote:

Geo, I will be honest and say, no I did not premix. I poured in a good batch of anti-freeze and then filled the rest with water..

I always wondered why the stuff wasn't sold premixed. Well, the other day I found some at NAPA premixed, and said, "Aha!" Brought it home and put some in the Ford and some in the Cub, pretty proud of myself. No mixing. Got thinking about it later and realized I'd paid as much for the premix as I did for a gallon of regular AF, which means the premix cost twice as much. My judgment's not as good as it used to be. Also, my judgment's not as good as it used to be.