Lower half of radiator stays cold while driving

[bavArian]

Hello everyone,

I took my A for a few trips in the last few days and, while it runs well now, I still have a problem with an overheating engine when driving uphill for extended periods of time or going faster than ~ 45 - 50 mph. (at an ambient temp. of ~70 °F)


First off some info:

- ran 50/50 water/antifreeze
- switched to straight water with diswasher tabs today
- timing was checked with a timing light, it's spot on; manual advance works
- no bubbles in the water with the engine running, just a constant stream of water from the pump
- carb is fine now, jets are within specs


What I noticed is that immediately after stopping when the car starts to overheat, the upper half of the radiator is hot but the lower half is relatively cool. It only gets hot 30 seconds (or more) after stopping.
I understand that the water should exit the rad cooler than it enters it (duh) but is it normal for the water to cool down so much? It seems to me that the heat transfer from the water to the rad is considerably worse in the lower half of the radiator. Idiot-me didn't think to check if the outlet of the rad is hot or cold, will do that on the next run.


I took it on a trip of about 30 mls today with the diswasher tabs in it and then emptied the rad. The water had a yellow/brownish hue and didn't look clean. I assume that's just dirt/grease from the past that's slowly being dissolved by the hot water?
Might add that the antifreeze-mixture that I ran previously had the same color.


Is there anything else I can do without removing the rad and backflushing it with a pump? Or should I just go for a few trips and change the water in between to see if it gets better?

Thanks,


Daniel

[Big hammer]

Alot of good information, but what are your symptoms of overheating? Coolant level cold should be under the baffle in the radiator. When I first bought my A I thought it was overheating, I was overfilling the radiator.

[bavArian]

Symptoms of my overheating engine are a fine spray of water through the radiator cap and, if I then keep driving fast, boiling water in the upper hose to the radiator. (probably boiling water in the head)
The spray may have been a slightly undersized quail-gasket. (there was absolutely no resistance when closing the quail)

Cut an addition gasket today and the quail closes with some resistance now which should be fine.



Coolant level cold is relatively low but it seems to find its own level and the thermoquail registers temperature just fine, so I assume that the waterflow coming from the engine is working as it should. Otherwise the quail would show low temperature as the water wouldn't reach the feeler of the quail.


Running water or 50/50 antifreeze didn't make a noticable change.


EDIT: Setting spark to full advance or 3/4 makes no difference, still overheating if I go full throttle for more than maybe a minute.

[Stingray70]

What type of radiator do you have? Some aftermarket units will cause trouble even if they are clean and clear. How is the physical condition of your radiator? Are any of the fins loose from the tubes?

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[bavArian]

Checked the fins some time ago, all seem tight.

The radiator seems quite old, from the pictures I can find via google I'd say it could be an original radiator. If it's a repro it is at the very least 30 years old.
I'll upload a pic of inside and outside tomorrow, maybe someone can identifiy it.

[Stingray70]

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Count the rows. Make sure it isn't a two row radiator.

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[1930artdeco]

Sounds like you are losing water and or have a plugged radiator. Mine used to puke out from under the cap and I had a lot of boulders in the upper tank. Or you are pressurizing it from an exhaust crack someplace. Do you have water coming out of the tail pipe?

Mike

[nkaminar]

Something is blocking the coolant flow. My advice is to buy a new radiator from Brass Works and make sure the flow through the engine is not blocked. Drain and save your 50/50 mixture. Remove any thermostat you may have. Fill the system with straight water. Remove the radiator cap. Remove the bottom radiator hose. The coolant should drain out of the radiator and engine within 2 to 3 seconds. You can do the test again by keeping the bottom radiator hose off and blocking both sides with something like a rubber balls. Then fill the system again with water and remove the balls one at a time to check the radiator and engine separately.

[jack backer]

Old radiators in good shape can be saved by removing and back flushing with a hot water pressure washer with degreaser, water pump grease and debris plug the tubes.. you need more heat and chemical than dishwasher tabs and engine temp. I know it’s painful to tear her down but cleaning it correctly will save money. Pulling the cylinder head and cleaning the water jacket finishes the job.

[bavArian]

More Info:


- no thermostat
- coolant level seems to stay constant once it has found its level
- when starting the fine spray of water the mercury is all the way to the top
- no water from the exhaust and no white or blue smoke
- checked the rad, it's a 2 row repro which has a tag 'Eureka' on it



From your answers there seems to be no way around removing the rad and flushing it properly. Then I'll just have to do that after the next car meet mid june.

I'll report back when I have the rad removed.


Also I will take my IR-thermometer with me on the next ride to get proper values from head and radiator.

[1crosscut]

Stick a dial meat thermometer directly into the coolant to get accurate temperature readings. Let us know what you are seeing.
The I.R. units are okay for a general idea of temp but the probe in the coolant is the best way to tell the actual temperature of the coolant.

[Gene F]

The radiator is bad.

When I got my car it was mostly fine, till it got worked hard, or if it was a real hot humid day then it would overheat. Turns out back in the day Sears made cheap radiators with not enough capacity. It could have a blockage, but why bother, just call Snyders and get the best one they sell, and be done with it. Seems like they were $585 last I looked. Do it now before you end up with bigger problems.

[bavArian]

Well, the only one in stock atm is 730 $. For me that's around 1100 $ including shipping. Hence I'll check to see if the current rad can be saved before considering a new one.

[WHN]

Originally Posted by bavArian

Well, the only one in stock atm is 730 $. For me that's around 1100 $ including shipping. Hence I'll check to see if the current rad can be saved before considering a new one.

Spend the money and move on to fixing the next problem.

Enjoy.

[ETAModel]

If you can find an old school radiator shop they can unsolder the top and bottom. Then vat the radiator and dissolve the crap that's blocking it. Then they should rod the radiator and solder the top and bottom on.
Now finding a shop who'll do this is harder these days. The local shop near me told me they'd sell me a new radiator but not vat or rod the old one.
The more I drive the better I get at controlling the temp, so I'm good RN.
I wish you luck.

[shew01]

An old school radiator shop can also swap out a plugged core for a new one, and keep the bottom and top tanks.


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[katy]

How is the outside of the radiator core? Can you see through it good? Or is it clogged w/several coats of paint? Dead bugs? Mud? Other crud?

[bavArian]

The radiator is clear of any dirt, mud or excess paint. I can clearly see through the fins. It definitely is not an airflow problem. It also has flat tubes, not round ones.
Btw., I have the engine pans installed as well.


I'm suspecting the lower part of the radiator is at least partially coated with grease or dirt, reducing the heat transfer from water to radiator.

I will probably take a look through the outlet when I have it on the workbench, maybe that will show me why the lower part of the radiator stays cool while driving but the water doesn't.

[eagle]

There are a lot of products out there to clean the radiator. I'd try one or two of those first. Radiator shop should be able to point you towards one that is effective enough to do the job.

[Stingray70]

Originally Posted by bavArian

Well, the only one in stock atm is 730 $. For me that's around 1100 $ including shipping. Hence I'll check to see if the current rad can be saved before considering a new one.

I know you dont want to hear this but I dont think that a 2 core radiator will ever work properly. No matter how good it looks. Don't waste time trying to get an inferior product to work.

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