Radiator flow rate

Great Lakes Greg

Great Lakes Greg

Well-known member
Is there an accepted seconds measure for a radiator to drain it's contents? By this, I mean fill the radiator to the top while holding my hand over the bottom pipe. Remove my hand and count the seconds to a full drain.
 
Just remember flow rate does not mean you have a good radiator. As radiators age, the fins loose contact with the tubes and you loose thermal transfer. In other words, you could have one that flows great but cools like poo.
 
redmodelt said:
Just remember flow rate does not mean you have a good radiator. As radiators age, the fins loose contact with the tubes and you loose thermal transfer. In other words, you could have one that flows great but cools like poo.
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Ditto, ditto, ditto.
 
When I had my radiator out of an engine change, I turned the radiator upside down and tried the flow test. What I found out is the rush of water flushed out about a shot glass of rust flakes! It emptied in about two seconds or less, the radiator may be 80 years old, but low mileage. For me it was a piece of mind wanted the best chance for the freshly rebuilt engine because a new engine needs help removing heat.
 
HA...Greg, I have always wondered that myself!

My thought however would be to take a few known originals which are super clean, fill with water as you suggest, and measure the AMOUNT of water in each.

Then compare those findings with some that have been in use for a while of the same types and just see what the difference would be in the discharge to determine a "clogged" raidator.

Interesting question!

Pluck
 
That filling the radiator and letting it drain is a very poor test of anything. If you question your flow rate, and you are running hot, then that old radiator is plugged. Most are and people try band aids until they buy a new one. Not worth the hassle. You asked about flow rate. It should flow about 36 GPM.
 
The syphon flow design of a Model A engine is 36 to 38 gpm.

This is needed to give you the 20 degree temperature difference between top of engine (outlet) and bottom of engine (inlet). Approximately 180 degrees top, 160 degrees bottom.

Most overheating problems that I have seen were fixed with a correct “new” radiator.

Paint, clogging, loose fins, leaking, anyone one or combination of all could be a problem.

A new radiator is just another item to check off on your “need to have” for a good runner list. Enjoy.
 
the cross section area of the combined tubes it much larger than the hose nipples ---many can be clogged and still get all the flow that can go through the hose nipples
 
When Chief had a radiator out, for awhile, he kept it FACE down & FULL of water. Then backflushed it, before he installed it. "Sometimes" he filled it with a LYE solution, to clean it better.
Chiefs' Son--Bill W.
 
If an 'A' is over heating, then the radiator may be the problem. Also one needs to check timing and it is best to remove the head and vacuum and blow compressed air through the water jackets, paying particular attention to the area at the back of the block. I worked on one yesterday and the water jacket in the engine was pretty full of all sorts of bits of stuff. Once cleaned out, we pressure tested the block with 40 pounds of air and it was fine. A new 'BEST' head gasket with copper coat on both sides and then cleaned out the water jacket in the head the same way and put it back together. About 6 hours work...the old girl fired right up and seemed happy. Ernie in Arizona
 
We have an industrial hot water pressure washer at the shop with quality chemical degreaser.Ive saved two radiators so far by flushing back and forth till the radiator gets good and hot.Water pump grease, debris and even some hard water deposits came out...at 500 bucks plus for a new one its worth a try..
 
Thank you for all of the answers. The car in question does not run hot, but rather pushes out water at high speeds (50 plus). It really makes a mess on the hood and windshield. The overflow tube is not plugged. New gasket on the cap, but it sneaks past the Quail flip top. I wanted to check if the radiator was handling what the pump is throwing at it. We are going to try a 160 thermostat to slow the flow down.
 
Great Lakes Greg said:
Thank you for all of the answers. The car in question does not run hot, but rather pushes out water at high speeds (50 plus). It really makes a mess on the hood and windshield. The overflow tube is not plugged. New gasket on the cap, but it sneaks past the Quail flip top. I wanted to check if the radiator was handling what the pump is throwing at it. We are going to try a 160 thermostat to slow the flow down.
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Be careful with thermostats. Model A’s were not designed to work with one. Remember, the Model A’s cooling system is mainly syphon flow, the pump is really only of any help at higher speeds.

Are you missing the top plate inside the radiator? It sounds to me like it’s not there. Or is your radiator not allowing the flow of coolant to past down and out the bottom equal to the out flow from engine?

Look in your radiator, there should be a plate there so what you are explaining will not happen.
 
Sounds like your main trouble is an ill fitting cap. I've seen some add an additional gasket made from a piece of inner tube to get a tighter fit. Keep working at getting a tight seal and the mess will go away.
Try running with a standard cap and allow the radiator to seek its comfortable water level. Too often a radiator is filled to the top and it will puke coolant out anyplace it can until if settles in at a level it is comfortable with. As long as the tubes in the radiator are covered you don't need to add any coolant.
 
From experience with my A, it sounds like first thing is you need to get your cap TIGHT. I have a repro Quail and NO leaks. Second off, don't refill your radiator over the baffle. I add a quart to mine every spring, when I run it then it pukes some out the overflow and then is fine for the rest of the summer. Finds the level it wants and stays there. Not sure why I always add in the spring but I guess it gives me some peace of mind. Remember, the water pump SUCKS the water through the engine and radiator, it can't "pile it up" in the top tank.
 
REMEMBER, rust flakes stuck in the upper radumator tubes, is the most COMMON cause of OVERHEATING!!---Be SURE to backflush it, once or twice a year!!!
No matter how much we clean the block & head, this OOOLD CAST IRON is just like a "factory", that produces ONLY RUST FLAKES, on a continual basis.
Rusty Bill W.
 
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