Lower half of radiator stays cold while driving

[31Tudor]

Original radiator depending on manufacturer:
Ford - 4 rows, 94 tubes
Flintlock - 4 rows, 109 tubes
McCord - 5 rows, 87 tubes

Then I counted about 7 fins per inch on my original 1928 radiator.

[31Tudor]

Original radiator depending on manufacturer:
Ford - 4 rows, 94 tubes
Flintlock - 4 rows, 109 tubes
McCord - 5 rows, 87 tubes

Then I counted about 7 fins per inch on my original 1928 radiator.

[bavArian]

Huh, they were round tubes I guess? Anyone have any idea how round vs. "elongated" (not sure about the name of the new ones) tubes behave regarding cooling capacity?

[31Tudor]

28-29 original radiators all had round tubes
30-31 original radiators were elongated or kind of oval - they had 102 tubes

[31Tudor]

28-29 original radiators all had round tubes
30-31 original radiators were elongated or kind of oval - they had 102 tubes

[Karl Wescott]

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Another thing to check is the impeller of the water pump. The flathead V8 guys often have an issue where at high speed/hot water the pump will cavatate and not move water, while moving water fine at low engine speed. To check this issue you would need to make sure the volume of water continues to increase from idle to full throttle.

[Karl Wescott]

A high tech thought to check the radiator itself is with a thermal imaging camera. This should be able to show gradual cooling (radiator fine, just not moving coolant) or an abrupt temperature change (showing a block in the radiator). These are expensive but you might be able to get the local Fire Brigade to show off their "cool" toys, while you show off your "hot" one.

[bavArian]

Update:

Took apart the entire cooling system today to backflush radiator and engine several times. Used 50/50 vinegar/water on the radiator and diluted amidosulfuric acid for the engine. Got a bit of rust and dirt out of engine and radiator but not much.
At least the radiator seems to drain faster now.


Took a look at the water pump as well. The impreller was a little rusty (not much) but there was no sign of cavitation marks on the 3 blade impreller. I doubt that's the / a problem.


While the fan belt was off I blocked off the water inlet of the engine and filled it up to the outlet. There are no bubbles coming from the engine when spinning up the engine hard or letting it run fast. So the head gasket seems to be fine.


What I did notice today was that the cylinder head warms up unevenly. The drivers side with the pistons warmed up moderately to around 50 °C / 122 °F while testing whereas the intake/manifold side was already at 85 °C / 185 °F. Coolant temp. was at ~ 53 °C / 127 °F.
Is that a normal behaviour?


I will definitely check that on the next test drive. What would be the reason for the manifold side to get much warmer than the rest of the engine? Blocked water passage?

[1crosscut]

I've always found the the passenger side #1 cylinder area is the quickest to warm and the heat generally soaks through the head from that point back to the rear.

[bavArian]

Took it for a short test drive again today. It was ~4 °C/ 7 °F colder today but I think the heat dissipation radiator to ambient is a little better. Still not good enough mind you, but I was able to drive continuously (@ ~ 40mph) without a boiling radiator and the temps actually went down when driving downhill.
I also found that one side of the radiator was considerably cooler right after stopping than the rest. After half a minute or so the entire rad. had a constant temperature, with a difference of about 6°C / 11 °F between top and bottom. So there's obviously still a few clogged tubes. I'll check with a local radiator shop how much removing and refitting both tanks would cost me. If it's reasonable I'll rod it out myself, if not I'll probably have to bite the bullet and order a new radiator.


Head-temperature was more even when driving, under 10 °F difference between cylinder and manifold side.


Question: Which temperature should the water have when entering the block?

I'm measuring ~ 80 °C / 176 °F at the lower tank leaving the radiator.

I assume that's around 15°C / 30 °F too hot?

[WHN]

Originally Posted by bavArian

Took it for a short test drive again today. It was ~4 °C/ 7 °F colder today but I think the heat dissipation radiator to ambient is a little better. Still not good enough mind you, but I was able to drive continuously (@ ~ 40mph) without a boiling radiator and the temps actually went down when driving downhill.
I also found that one side of the radiator was considerably cooler right after stopping than the rest. After half a minute or so the entire rad. had a constant temperature, with a difference of about 6°C / 11 °F between top and bottom. So there's obviously still a few clogged tubes. I'll check with a local radiator shop how much removing and refitting both tanks would cost me. If it's reasonable I'll rod it out myself, if not I'll probably have to bite the bullet and order a new radiator.


Head-temperature was more even when driving, under 10 °F difference between cylinder and manifold side.


Question: Which temperature should the water have when entering the block?

I'm measuring ~ 80 °C / 176 °F at the lower tank leaving the radiator.

I assume that's around 15°C / 30 °F too hot?

To hot.

Get a new radiator. If you are planning on driving the car. You need a good cooling system. Somethings need to be right. This is one of them.

[nkaminar]

I think you should "bite the bullet" as you say. I don't know about where you are but here lots of Model A parts are listed on Craigslist.org. You may be able to find a good used radiator locally. Just make sure it has lots of tubes, is clean inside, and has lots of fins. Compare with what you have. Or order new from Brass Works or Snyders or another vendor.

[bavArian]

Haven't seen a "good" radiator here in Germany for the A. The only available ones are the cheap aluminum rads, but they seem to have fitment problems and they look abysmal to be honest.
You can also get used ones, but chances are that they have the same problem as my current one, so that's out of the question as well.

[katy]

It sounds like there may be something blocking part of the top of the core, possibly a loose baffle, possibly some foreign material?

[Gene F]

Do you think you are gaining any ground? Your comment about draining faster.... there is a driveway test as to how long a radiator should drain, but I don't recall it. Perhaps someone will chime in, with how many gallons/litres it holds too.

[bavArian]

Originally Posted by katy

It sounds like there may be something blocking part of the top of the core, possibly a loose baffle, possibly some foreign material?

Hmm, I can't hear anything loose inside the rad. Tilted and shaked it enough in the cleaning process.
Anyway I'll take a borescope and check the tanks as soon as I have time to do so.

Originally Posted by Gene F

Do you think you are gaining any ground? Your comment about draining faster.... there is a driveway test as to how long a radiator should drain, but I don't recall it.

The radiator does drain a bit faster after the cleaning, it takes around 3 to 4 seconds I would say for it to just trickle out of the outlet. Also I think the cooling was improved, it's just not good enough for hot weather.

[CT Jack]

Based on what you are reporting it sounds you definitely have a plugged radiator. I submitted a post #31 that suggests you remove the radiator and have a radiator repair mechanic clean it. If you have the correct radiator and the metal (brass) is in good condition they can unsolder one of the covers and brush the inside of each tube. This will clear out any blockage and also improve heat transfer. Do not allow them to pressurize the radiator it is not designed to be pressurized and will cause damage.

[nkaminar]

Here is another idea. There is a thing called "Water Wetter" that is supposed to lower the coolant temperature. You could try running that and just water, no antifreeze. Drain it out and save it during the winter where you will need the antifreeze.

Many year ago, before my time, when only water was used, people would drain their radiators while they were at work in the winter so the block would not freeze. They would have to pour the water back in before they could drive home. Not sure how they kept the water from freezing, maybe they wrapped the container in a blanket.

By the way, the radiator should drain in 2 to 3 seconds. 3 to 4 is not bad and may just indicate that there are a reduced number of tubes. Or may indicate that some tubes are blocked, as Jack said.

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