1941 cooling

[TomC750]

I have the running of my '41 Merc pretty well sorted out. Turned out I had both a bad condenser as well as carb issues. But now I have other concerns.

When running it a while in 80 or more temps, the temp gauge is 3/4 the way up the scale and the oil pressure is 20SI cruising and only 3PSI or so at idle. When I let it set for a short while it is around 10 PSI at idle. The result is the same whether running 30wt or 15-40. At cooler temperatures with temp gauge in the middle the oil pressure holds up better. The oil pressure readings are the same with the stock gauge or a mechanical one.

So, I am wondering this: Given that 41's are subject to cooling issues due to fan being positioned low on radiator, might I be better off by bringing the coolant temp down to start with? I think a good solution for this would be an electric fan, which I would rather not do, as it would likely necessitate changing to 12V. Open to ideas.

By the way the engine seems to be in good shape with no smoke or oil burning. It is very quiet.

[JayChicago]

Originally Posted by TomC750

might I be better off by bringing the coolant temp down to start with?

Once up to that warm/hot range, all thermostats will be wide open just the same. Opening at a lower temp may just delay things 5 or 10 minutes.

Likely suspect is the condition of the radiator.

[mcgarrett]

I have a '40 Tudor with similar cooling concerns on hot days here in Texas. '39, '40, and '41 had the fan mounted on the end of the crankshaft and was not one of Ford's better ideas . I had thought about maybe adding one of these...

https://www.speedwaymotors.com/Speed...Fan,56152.html

I would probably go with the big 16" unit. Since it can be converted to be a "pusher" by reversing the wires, it would be easier to install it in front of the radiator which would also help to conceal it somewhat.

[JayChicago]

Originally Posted by TomC750

The oil pressure readings are the same with the stock gauge or a mechanical one.

Good to hear a report that the stock gauge/sender is accurate. Makes me feel a little better about trusting my gauge.

[JayChicago]

Don't understand why a fan low on the radiator is considered a negative. Seems like it should remove heat just as well.

BTW, the fan is needed only at low speeds. When moving, ram air thru the radiator is doing the cooling.

[mcgarrett]

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Originally Posted by JayChicago

Don't understand why a fan low on the radiator is considered a negative. Seems like it should remove heat just as well, maybe better.

The crankshaft mounted fan only turns at engine speed which limits its ability to move enough air. If a radiator is dirty or is in poor overall condition it compounds the problems of heat transfer and makes air movement even more critical. That slow moving, crank-mounted fan just won't do the job. Ford engineers realized this and changed the design back to a fan mounted on a separate idler pulley that increased the fan speed above crankshaft speed.

[cadillac512]

The temp gauge in my '41 Merc runs 3/4 gauge all the time with 180 thermostats. Full scale hot is approx 212-215 degrees. If you're not losing water it's not running too hot. As for oil pressure, first thing to do is test it with a mechanical gauge. You may find it's higher than the dash unit says. However, even if it's running as low as it shows it'll still do just fine and run a long time like it is.

[fortyonerag]

I rebuilt the radiator when I got my 41. Flushed the block (garden hose) and replaced water pumps (noisy).

On hot days it seems to get to around 180 and stay there, although I haven't pushed my luck in stop start traffic.

Interesting that a mech oil gauge gives you the same reading as the old stock set up. I thought I had low oil pressure until I hooked up a capillary SW unit.

[corvette8n]

I suggest cleaning and flushing the block and radiator, checking the thermostats in a pan of water to see if they are opening at the correct temperature, are your water pumps in good condition?

[Seth Swoboda]

I will agree with the others. The radiator needs to be 100% clean and no tubes blocked. This will allow your system to cool properly. I have checked my stock temp gauges against an inferred thermometer and found that the OEM dash gauge reads higher than actual temperature. As for the oil pressure, what is the condition of your main bearings? Is this a new engine or an older engine with many miles? I would not be concerned with either at the moment. If you are not boiling water out the overflow tube, it's not as hot as you might think.

[TJ]

I agree with others that you need to clean the radiator and flush the block.

[TomC750]

Originally Posted by Seth Swoboda

I will agree with the others. The radiator needs to be 100% clean and no tubes blocked. This will allow your system to cool properly. I have checked my stock temp gauges against an inferred thermometer and found that the OEM dash gauge reads higher than actual temperature. As for the oil pressure, what is the condition of your main bearings? Is this a new engine or an older engine with many miles? I would not be concerned with either at the moment. If you are not boiling water out the overflow tube, it's not as hot as you might think.

My problem is that I know nothing of the car's history as to the true mileage. It looks to me that the engine it has never been apart! The radiator looks new, although it may be just that the car was in really good shape prior to the frame off restoration. It looks to me that the restorers were body people and not mechanics. I will assess the main bearings when I install a new rear main seal, drips slightly after running. In the meantime I will flush radiator. Silly me, I did not think of using my laser interferometer to check eng temp.

Good conversation from all.

[TomC750]

Originally Posted by corvette8n

I suggest cleaning and flushing the block and radiator, checking the thermostats in a pan of water to see if they are opening at the correct temperature, are your water pumps in good condition?

Pumps don't leak, otherwise my experience with flathead pumps is that is all that matters. If I flush the radiator and block, what is your procedure, vinegar or commercial product?

[ford38v8]

A cleaning of the cooling system is always a good idea, but as you haven't reported boil -over or losing coolant, I see no imperative that it must be done just now. When you do it, though, be sure to flush it out in the prescribed timeframe, as the caustic does continue to work on the internals.
Your oil pressure is normal, any reading at all at idle shows nothing to be concerned about.
Electric fans are not usually a good choice for a flathead, for several reasons. High or low placement not near as important as some would tell you. What you can do here with really good results is to make sure your radiator's air dams are in position, and to ensure that the fan's position is close to the radiator.
You said the radiator appears to be in a fairly new condition, but a close examination may show otherwise. The tubes must of course be clear for water flow, and the fins open, not bent for air flow, but also, and this is often overlooked, the fins must be solidly connected (soldered) to the tubes for heat transfer. Heat transfewr can also be impaired if there is too much paint on the radiator. A very light application of rattlecan flat black is all you want.
Again, no boil-over, a temp gauge reading not pegged out, and an oil pressure reading that actually moves the needle, enjoy your Ford and don't worry about it.

[TomC750]

Originally Posted by mcgarrett

I have a '40 Tudor with similar cooling concerns on hot days here in Texas. '39, '40, and '41 had the fan mounted on the end of the crankshaft and was not one of Ford's better ideas . I had thought about maybe adding one of these...

https://www.speedwaymotors.com/Speed...Fan,56152.html

I would probably go with the big 16" unit. Since it can be converted to be a "pusher" by reversing the wires, it would be easier to install it in front of the radiator which would also help to conceal it somewhat.

Thanks for the link, very helpful.

[TomC750]

Originally Posted by ford38v8

A cleaning of the cooling system is always a good idea, but as you haven't reported boil -over or losing coolant, I see no imperative that it must be done just now. When you do it, though, be sure to flush it out in the prescribed timeframe, as the caustic does continue to work on the internals.
Your oil pressure is normal, any reading at all at idle shows nothing to be concerned about.
Electric fans are not usually a good choice for a flathead, for several reasons. High or low placement not near as important as some would tell you. What you can do here with really good results is to make sure your radiator's air dams are in position, and to ensure that the fan's position is close to the radiator.
You said the radiator appears to be in a fairly new condition, but a close examination may show otherwise. The tubes must of course be clear for water flow, and the fins open, not bent for air flow, but also, and this is often overlooked, the fins must be solidly connected (soldered) to the tubes for heat transfer. Heat transfewr can also be impaired if there is too much paint on the radiator. A very light application of rattlecan flat black is all you want.
Again, no boil-over, a temp gauge reading not pegged out, and an oil pressure reading that actually moves the needle, enjoy your Ford and don't worry about it.

Thanks for your reassuring perspective. Appreciate it. Yes, although the radiator looks brand new, I will do the flush.

[Seth Swoboda]

Several years ago, I had a radiator out of a car for a while during an engine rebuild. The radiator was in good condition. When I put the car back together, the engine got hot and it did boil over. I double checked head torque, ignition timing....still boiled over. I thought about it for a while and the only variable that was not addressed was the radiator.

I took the radiator out and to an actual radiator shop. What happened was while the radiator was out it dried out inside. There was dried out sludge and slime that came loose. When I refilled the radiator all that junk that had dried out plugged up the tubes. The shop rodded out and hot tanked the radiator.

The shop owner told me that if I ever have a radiator out for an extended time, have it thoroughly cleaned.

[TJ]

Electrolysis can plug up the tubes in a radiator. Especially if a car has sat for awhile and not run. Drain the radiator and then look in the neck of the radiator and you may see mineral deposits around the edge of the tubes. If you see the deposits you can bet some of the tubes have the deposits down in the tubes.

[TomC750]

TJ, I am on that track, thanks.

[38 coupe]

I agree with ford38v8, you don't have a problem to fix. 3/4 hot on a stock gauge is 180 F, normal operating temperature for a flathead V8. What you have is an engine with wear, but not worn so bad it needs a rebuild. If there is any oil pressure at idle, and no bad sounds, then drive with confidence.