VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 Radiator efficiency and flow-thru rate

Today I was tinkering with my '49 Chevy 4400 - I wanted to take out the rear block drain fitting and make sure there isn't any gunk build up. I started to do that once before, but I was actually doing something else with the truck at the time and didn't. Today I did and after getting the fitting out and running a small wire in the hole, the engine coolant ran out in a nice, clean stream. This after it had been running for a wihle.

I tinkered with the timing some more then put it back together with new coolant (less than half and half).

Now the truck overheats. It didn't before. I must have stirred up the stuff in the engine block and it got into the radiator, but that seems far-fetched to me.

I will pull the radiator tonight and have it flushed tomorrow at the radiator shop in town. I need a spare, clean radiator like I have for the tractors. With my tractors, if I suspect a radiator, I can just switch it out and see if the radiator is the problem.

It is odd to me that water flows through the radiator as fast as I pour it in. I'm trying to understand how a radiator with a good flow rate can be stopped up to the point that it cools poorly.

It may be this: if, say, 30% of the tubes are unclogged, and that is enough for a good flow-through (from top to bottom) but, say, 70% of the tubes need to be unclogged for efficient cooling, then the 'flow-thru' rate is not a good indicator of the condition of the radiator.


Lee Prairie

(1) What are you considering as an "overheat condition" ...what is actually happening?

(2) Did you retard the timing?

(3) If you are using a t/stat, is it staying closed? Is water flowing through the system? Newer t/stats will fail in the open position.

Bob

Thanks for your post, Bob. No thermostat. The water/coolant boils out. It wasn't doing that before.... The engine runs well - it just overheats and boils out the coolant, which is mostly water now.

Lee

Perhaps there is air in the system.

Loose crud moving to the top of the radiator and/or air in the coolant are definitely the most likely causes.

Did the reverse flush with my '50 216 earlier this summer and that did the trick for my situation. I did the block and radiator separately.

Dean

Dean, before I posted, I went back and read your thread titled "running hotter than normal". The thing that was confusing to me was that water seemed to flow through the radiator well. It looked to me like the water ran out the bottom as fast as I could pour it in the top. With such a good flow-thru rate, it didn't seem like the radiator could be the problem.

I have it back from the radiator shop now, and I will put it back in and test it this morning. The radiator shop said many of the cooling tubes were plugged. It was a 'dirty' radiator despite the good flow-thru rate.

Lee

Even though a radiator has a good flow rate, that doesn't necessary mean that the radiator is still efficient on the heat transfer for cooling.

Well... that was it. With the clean radiator, it doesn't overheat anymore.

This was a big lesson for me because I always used the flow-thru test to judge the condition of the radiator. In this case, the flow-thru was good, but the radiator was dirty enough that if didn't have the cooling capacity it needs.

Lee

Glad you got it solved, Lee.

Dean

Took her out for a 20 mile road test. It's 80 degrees here in (close to) Brookings, SD. Kept her up to 40+ mph and no overheating problem. It was a dirty radiator that had a good flow-thru rate.

I am still unhappy with the timing situation. I can make the engine run very well with about 10 mpg mileage by adjusting the distributor, carburetor settings and choke. I'm not happy with that, but it runs well.


I had a dream that I installed a front wheel bearing backwards when putting the hub/wheel back after putting a kit in the brake cylinder. Is that even possible?

Lee